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ARTIFICIAL LIGHT

AND ITS

APPLICATION IN THE HOME

ARTIFICIAL LIGHT

AND ITS

APPLICATION IN THE HOME

PREPARED BY

The Committee on Residence Lighting

of Illuminating Engineering Society

MARIQUITA DYGERT, Chairman

Contributing Authors Collaborating Authors

E. W. COMMERY D. W. ATWATER

MARIQUITA DYGERT ELOISE DAVISON

HELEN W. HARDY P. S. MILLAR

M. LUCKIESH ELIZABETH MURRAY

HELEN G. MCKINLAY FRANCES M. ROSENBERG

MARY E. WEBBER SARAI WAUGH

Sponsored by the Illuminating
Engineering Society, New York

FIRST EDITION

McGRAW-HILL BOOK COMPANY, INC.

NEW YORK AND LONDON
1932

PRINTED IN THE UNITED STATES OF AMERICA

parts thereof, may not be reproduced

in any form without permission of

the publishers.

THE MAPLE PRESS COMPANY, YORK, PA,

FOREWORD

The aim of this book is to present a practical, con-
cise, and reliable treatment of artificial lighting and its
application in the home. It is hoped that this text-
book, which contains the fundamental concepts and
the practical interpretations and applications of light
in the home, may satisfy the demands for information
on the part of colleges, universities, normal schools, and
other places where instruction is centered on training
in the various phases of house planning and home
economics.

Since the printed sources of home-lighting informa-
tion have been scattered, difficult to locate, and not
especially prepared for this apparent need, the Illuminat-
ing Engineering Society undertook the preparation of
this book.

Although it is designed primarily as a textbook, it is
hoped that, because of its simple, non-technical style,
it may prove a suitable source of information to the
home keeper herself, who is more and more interested
in the best methods of utilizing artificial light in the
home.

This book has been prepared by specialists who have
devoted either all or a large part of their time and efforts
to the development of the art of home lighting, and,
accordingly, this compilation includes the underlying
fundamentals and practices gained from their researches,
observations and experiences.

CONTENTS

PAGE

FOREWORD v

CHAPTER I

LIGHT AND PEOPLE 1

Progressive Steps in Historic Light Sources — Modern Illum-
inants — Unusual Developments — Photoelectric Tube — Safety
Factors of Light — Light and Vision — Light, Radiation and
Health.

CHAPTER II

FUNDAMENTALS OF LIGHTING 11

Comparisons of Daylight and Artificial Lighting — Effect of
Position and Size of Light-source — Control of Brightness —
Application of These Principles — Table of Reflection-factors of
Colored Surfaces.

CHAPTER III

CHARACTERISTICS OF INCANDESCENT LAMPS 22

Incandescence — Lamp Efficiency — Vacuum and Gas-filled
Lamps — Shapes and Sizes of Lamp Bulbs — Lamp Bases —
Frosted Lamps — Daylight Lamps — Lamp Life — Carbon Lamps
— Table of Application of Lamps in Residence Lighting.

CHAPTER IV

LIGHT AND COLOR 31

Rainbow Composition of Light — Pigment Colors — Color in
Light — Difference between Pigment Colors and Color of Light
Explained — Table of Additive Primary Combinations (light
mixtures) and Subtractive Primary Combinations (pigment
mixtures) — Table of Some Apparent Color Changes Produced
by Contrast Effected by Color Surroundings and Size of Area —
Psychological Significance of Color and Its Effects — Effect of
Colored Light on Colored Objects — Use of Colored Light in the
Home.

CHAPTER V

FUNDAMENTALS OF ELECTRICITY 44

History of Electricity — Conductors and Insulators — Units of
Measuring Electricity — Ohm's Law Explained — Electrical Cir-
cuits— Measurements of Power — Measurements of the Use of
Electricity — Explanation of Meter Reading — How to Compute
Cost of Operating Lamps and Appliances.

vii

viii CONTENTS

PAGE

CHAPTER VI

WIRING FOR THE HOME 53

Electrical Circuits and Principal Wiring Methods Explained —
Requirements and Recommendations for Numbers and Position
of Lighting-outlets, Wall Switches, and Convenience-outlets in
Every Room — Table of Wiring Symbols.

CHAPTER VII

LIGHTING EQUIPMENT 74

Systems of Direct, Semi-indirect, and Totally Indirect Lighting
Explained — Recommended Types of Lighting Fixtures — His-
tory of Fixture Design — Shading Media of Silk, Parchment, and
Glass — Table and Floor Lamps — Modern Lighting Equipment
and Its Trend — Specifications for Evaluating Lighting Fixtures.

CHAPTER VIII

LIGHTING THE ROOMS OF THE HOME 93

Convenience, Eye and Nerve Comfort, Charm and Beauty Goal
of Good Lighting — Requirements at Entrance — Flexible Light-
ing for Living Rooms — Varied Suggestions for Dining-table
Lighting — Requirements and How to Fulfill Them in Kitchen
Lighting — Lighting of Bedroom and Bath — Garage, Closets,
Sewing Room, Basement, and Attic Lighting Suggestions —
Sizes of Lamp Bulbs Recommended Throughout.

DICTIONARY OF ILLUMINATION TERMS 129

QUESTIONS COVERING EACH CHAPTER 139

INDEX . . 143

ARTIFICIAL LIGHT

AND ITS APPLICATION IN THE
HOME

CHAPTER I
LIGHT AND PEOPLE

As man developed he gradually realized that during
each twenty-four hour period one of his most important
senses, that of vision, became useless. To his prob-
able terror and bewilderment the light faded and things
were blotted out into an inky blackness. While this
condition lasted, he was able to see little or nothing
and became especially aware of the dangers, which,
because of their uncertainty, seemed much more formi-
dable than they really were. Because of these lurking
dangers and the insecurity of darkness, the pursuits
of man were of necessity limited to the daylight hours.
The absence of light became a crippling, paralyzing
factor and a severe handicap to pride, which was an
ever present influence differentiating man from the
beasts. It was only the sun each morning which could
sufficiently renew his confidence in himself, and quite
logically it became his god.

The effort to combat darkness symbolizes one of the
first important steps in the progress of the human race.
Light from the sun, moon, and stars brought a certain
amount of confidence and serenity. On the other hand,
light that was reflected in the eyes of wild animals, that
from lightning, the aurora borealis was of a different order
and probably filled mankind with awe and terror. Evi-

2 LIGHT IN THE HOME

dently light was for the most part a benign god but at
least was a whimsical one and rather irregular as the
seasons progressed. Distinctly light was not controllable.
Distinctly it was not portable. Quite certainly, too, the
amount of light which could be placed at a given point was
beyond the power of man to control. The bonfire, which
primarily provided warmth and protection for the physical
being, soon manifested itself as a means of surmounting
the overpowering darkness. Before long, human intelli-
gence prompted the removal of a burning brand from
the fire, thus somewhat feebly enlarging the range of
vision after sunset and lengthening the hours of activity.
How long this method was used is more or less conjecture,
but selection eventually took place and certain vegetable
matter that contained oil and pitch was used, thereby
producing a better vehicle for light.

Development of Light Sources.

As time progressed, oil lamps were made out of natural
receptacles such as hollowed-out stones, and later a
crude wick was found to be valuable in the operation
of such a lamp. Gradually, yet slowly, these utensils
were fashioned to meet the advancement of civilization,
and the plasticity of clay brought a variety of shapes.
Bronze, a more permanent and beautiful medium, came
into use later. These, refined through decoration, very
often were fashioned for multiple wicks, showing always
the desire for more and better light. The utility of
lamps was then enhanced by suspending them from
walls or ceilings or by raising and lowering them on
pedestals.

In most countries the hand lamp seemed to be most
useful and dates back in use to ancient Egypt, China,
Greece, Rome and, at a much later date, again found
its place in colonial America.

Beeswax and tallow candles were used throughout
the Christian era. In fact, some authorities feel that

LIGHT AND PEOPLE 3

they were invented by the Phoenicians. Candles
have long held a very conspicuous place in the rituals
of many religions of the world. Massive brass and
bronze candelabra were used for state and religious
purposes, sometimes singly and often in pairs, a custom
that is practiced even to the present day.

Beautiful craftsmanship developed massive chandeliers,
brackets, and tripods for oil and candles. It was not
until about the middle of the nineteenth century that
camphine (turpentine and alcohol) was used because of
the improvement in the light which the burning of this
mixture produced. Close on the heels of camphine
came kerosene, which still holds a place in lighting in
the more remote parts of this country.

Gas, until the advent of the Welsbach mantle, was only
a moderate improvement as far as light was concerned.
It did, however, eliminate some of the drudgery of filling
and cleaning oil lamps. From the use of gas resulted
the term ''fixture," since the earlier and more generally
devised arrangements for this illuminant required a
fixed position for its use. The necessary piping created
this immobility.

The advent of electricity meant the use of an illu-
minant that was for the first time safe, clean, portable,
and one that promised more comfort than was obtain-
able from the flickering flame of the oil lamp, tallow
candle, or gas jet. The first incandescent lamp to be
generally used was developed in 1879 by Thomas A.
Edison and produced light equal in amount to that
of 16 candles. Since that time this original lamp has
been developed into a great number of varieties which
have not only interesting and romantic but also almost
limitless applications. For example, aviation beacons
now guide planes in their flight and make possible the
night air mail. Outdoor sports, including football and
baseball, are played by the light of the modern incandes-
cent lamps. Vehicular traffic in underground tunnels is

4 LIGHT IN THE HOME

made possible. Divers now explore the depths of the
sea and are helped in salvaging operations by incandes-
cent lamps designed for under-water service.

Unusual Developments.

It was less than ten years ago that Elihu Thomson
and his assistants in his research laboratory bent light
around a corner, took it out of the bulb, and put it into
a quartz rod which obligingly carried it over several feet
of distance without perceptible loss. Not long ago
light was " frozen" in Schenectady, New York, put into
a thermos bottle containing liquid air, and carried on
a train more than 100 miles. When the material
involved was warmed, the light trapped in Schenectady
escaped in New York City.

Even sources, the radiations of which cannot be seen
without special preparation on the part of the man
who wants to see them, have been developed. Sources
whose radiations go through a steel wall, and which
penetrate the internal cavities of the human organism,
or which can be bent around corners, have been developed.

In addition to light-source developments, there has
also been developed a device which, like the human
eye, is sensitive to light. This has been referred to
as an " electric eye/' However, it is correctly termed
the photoelectric tube. Its appearance is not unlike
an ordinary lamp bulb, except that its inner surface
is silvered like a mirror. In place of a filament it has
in its center what might be called a small target, while
on part of the inner mirrored bulb surface there is a
very thin coating of a metal such as potassium, caesium,
or rubidium. Directly opposite the surface covered with
the thin metal layer there exists a small opening in the
silvered inner surface of the bulb through which the
light is admitted. Light, upon entering this cell,
is readily detected by instruments connected to the
inner surface of the bulb and the center " target,"

LIGHT AND PEOPLE 5

although the entering light must strike the thin metal
coating of potassium, caesium, or rubidium to have this
action take place. Changes in amounts of light entering
the cell produce changes in the amount of current flow-
ing through it. These changes of current, while very
small in value, can be amplified, making it, in turn,
possible to operate electric switches and other devices.

The applications of this combination are many and
varied. Artificial lighting may be turned on automati-
cally at the end of the day and turned off at sunrise.
Indoors in offices and schoolrooms artificial lighting
may be turned on automatically when the daylight
falls below a predetermined value. Automobiles pass-
ing through tunnels are automatically counted as each
car in passing interrupts a beam of light which is directed
at a photoelectric tube. The variation in color of
various products can be recorded by the photoelectric
tube, inasmuch as the differences in the amounts of
reflected light are readily detected. These few applica-
tion cases are given merely to emphasize further some
of the wonders of light, electricity, and man's accomplish-
ments with them.

It is fair to conclude that artificial light has been
exceedingly important in permitting man to move
indoors and that it has provided certain compensating
luxuries for the change in the habits of races. Whether
it be for better or worse may be argued, but not the
fact that it has played no small part in the creation
of the home, the apartment, the office, and the factory.
This influence is particularly well illustrated in some
recently built structures wherein all windows have been
eliminated and all light is obtained from well-designed
artificial lighting systems.

Safety.

We find a natural heritage in the fact that light is
generally associated with safety. Perhaps one of the

6 LIGHT IN THE HOME

most dramatic illustrations is the signal system of rail-
roads, particularly underground railroads such. as sub-
ways, where trains whiz along at the rate of a mile
a minute less than five blocks apart, and the really
controlling factor is light signals. It is still more effec-
tive than all the punishments ever invented to combat
crime. Daylight robberies and attacks are only for
the most courageous or the most insane. The time
for the typical prowler today and five thousand years
ago was during darkness.

Light and Vision.

Relative values of our separate senses in acquiring
knowledge give the visual sense first place. It is worthy
of note also that a very high percentage of all muscular
activity depends upon our ability to see — in other words,
three-fourths of our work and play reverts to the eyes for
guidance.

Primitive man in being out of doors used his eyes
under intensities of illumination ranging from a few
thousand to 10,000 foot-candles. Since a foot-candle
is the illumination produced by a standard candle 1
foot away from the surface illuminated, it is seen that
it requires the equivalent of 10,000 lighted candles,
all concentrated into a single candle, 1 foot away from
a surface to equal this sunlight intensity of illumination.
Man today, however, living indoors, has quite changed
the conditions under which he uses his eyes. Unless
sunlight is streaming through windows, daylight intensi-
ties indoors are usually not more than 50 foot-candles,
even though we are within 2 or 3 feet of the windows.
Move away from the windows and the intensity of
illumination usually falls to 8 or 10 foot-candles, and
in many rooms there are plenty of areas where the value
would be not more than 1 or 2 foot-candles. Couple
this greatly lessened value under which we so often
use our eyes with the fact that closer visual tasks over

LIGHT AND PEOPLE 7

longer periods of time are involved, and we obtain a
better appreciation of the desirability of the very best
artificial lighting that can be produced. Using the eyes
for close visual work under the prevalent conditions
of low intensities of illumination has been -likened to
the driving of an automobile in "low gear." Such
driving places undue and unnecessary wear and tear
on the mechanism when engaged in for long periods
of time. It is not unreasonable to assume that the
eyes used in "low gear" would suffer similar impairment.
Poor health, accidents, inferiority complexes, and
backwardness in school and in the social world can
often be attributed to defective vision — a condition
frequently brought about by the employment of the
eyes in close work. Good general lighting in combina-
tion with properly placed localized lighting minimizes
eye strain. Lighting which fails to do this satisfactorily
is ineffective and is characterized primarily by the
following negative factors:

1. Inadequate amounts of lighting.

2. Glaring lighting.

3. Spotty and excessively uneven lighting.

Proper lighting conditions include adequate amounts of
light, shaded light, and properly placed light. Proper
lighting accompanied by correct reading posture defi-
nitely provides improved seeing. This fact is demon-
strable. The average inertia of human beings, however,
is such that a single recitation of such simple statements
scarcely ever leads the listener to examine his or her home
for possible defects.

While the earlier specialists in vision and in lighting,
respectively, did not approach the final product, seeing,
in its fullest sense, we are today building what is termed
the "science of seeing." The correction of eye defects
with glasses does not go all the way any more than just
supplying light with which to see. Furthermore, there
are a number of psychophysiological sciences involved

8 LIGHT IN THE HOME

in lighting which are just coming to be appre-
ciated. The science of seeing, on the other hand,
recognizes the importance of the partnership of light
and vision, and the seeing specialist, a product of our
day, will eventually provide us with information on the
best combination of conditions which will enable us
to see most easily, most accurately, most safely, most
quickly, and most comfortably. In the final sense he is
concerned with the greatest productiveness and with com-
plete conservation of vision and other human resources
which are drained through the process of seeing.

Light of the right sort not only conserves vision
but lends more to the charm of a home than is generally
appreciated. One of the greatest obstacles to its adop-
tion is lack of appreciation of its potentialities. Con-
trary to a general misconception, satisfactory lighting
is not expensive. Furthermore, no one has ever regretted
the additional effort which may be involved in planning
for the comfort and convenience which it can provide.
That we are usually living with inadequate amounts of
light has been proved in the laboratory and in the home
itself. It is unusual to find people changing to lessened
amounts of light after they have lived with properly
distributed levels of lighting which insure comfort and
freedom from eye strain.

Light, Radiation, and Health.

There has always been a health aspect in lighting.
Improper and inadequate lighting impairs eyesight and
unnecessarily wastes human resources through eye strain,
fatigue, and various disorders. Lighting should be
adequate in quantity to enable eyes to see easily, quickly,
and comfortably. Humanitarian lighting aims to make
the eyes most productive with the least drain upon
human beings.

Recently, artificial light has extended its service to
mankind by supplying ultraviolet radiation for health

LIGHT AND PEOPLE 9

along with light for seeing. Summer sunlight is now
known to be beneficial to health. The particularly
effective radiation, as far as is known at present, is the
ultraviolet rays of wave lengths near the short-wave end
of the solar spectrum. High-powered sources of ultra-
violet radiation have been serving well in professional
therapy for many years. These sources emit ultraviolet
radiation throughout a great range of wave lengths. The
short-wave ultraviolet radiation is harmful to the eyes,
causing conjunctivitis or inflammation of the outer
membrane. Therefore, in order to make the radiation
safe for public use in the maintenance of health, filters
had to be developed which absorbed the harmful rays
and transmitted the beneficial ones. Ordinary glass
accomplishes the former but not the latter.

Safe sources of light and beneficial ultraviolet radiation
are now available. Naturally, the early stage of utiliza-
tion of this artificial sunlight is that of the portable
11 treatment" sun lamp. Children need sunlight or its
artificial equivalent in order to develop properly.
Rickets is cured and, better still, prevented. A child
with rickets is handicapped by a deficiency in bones,
teeth, blood, and muscles. Even after the cure is
effected, it is suspected that a handicap lingers for years.
Inasmuch as ultraviolet radiation is beneficial or even
essential to life processes, it seems probable that it is
important to healthy adults.

A natural goal of artificial lighting is to provide all the
benefits of summer sunlight. Artificial lighting is now
crossing the threshold into dual-purpose lighting. New
fixtures and lighting systems are necessary in order to
conserve the beneficial ultraviolet while diffusing the
light. Many advances have already been made along
this line. Researches are determining the threshold
dosages of ultraviolet radiation. Time of exposure to
ultraviolet radiation is an important factor as well as
intensity of this radiation. It is already known that

10 LIGHT IN THE HOME

surprisingly small dosages daily will produce beneficial
results. In dual-purpose lighting the public must rely
upon the knowledge and integrity of the lighting pro-
fession. Ultraviolet radiation cannot be seen directly;
therefore, too much may be obtained before the harm is
discovered or too little may be supplied.

The development of dual-purpose lighting which
supplies the beneficence of ultraviolet radiation along
with light for seeing is now an established fact. It can
be installed so that exposure to it may be as indiscrim-
inate as exposure to sunlight without harmful results.
Excessive dosages of safe ultraviolet radiation manifest
themselves by sunburn. No other harmful effect is
known.

CHAPTER II
FUNDAMENTALS OF LIGHTING

Size of Light Source.

A study of light and shade in nature is most helpful
in creating a concept of artificial-lighting fundamentals.
The artist appreciates this, for he spends many hours
studying nature with brush and crayon. First, the
chief sources of light in nature — the sun and the sky —
and the varied combinations of light from both, afford
us excellent examples of one of the most important
phases of lighting — the size of the source from which
the lighting is obtained. An overcast sky (sun not
visible) illustrates the results obtained when all of the
light comes from a very large area. If one were to walk
on an open road in a level country on such a day, the
shadow of one's self falling on the road would be difficult
to detect. Furthermore, the eyes feel comfortable under
this condition, and there is little or no desire to wear
sun glasses. If indoors the ceiling and walls of a room are
illuminated with a lighting fixture in which the lamps are
not visible and the fixture itself is opaque, the lighting
effect is very similar to that found outdoors on an over-
cast day. Shadows are exceedingly soft and eye comfort
is assured. Reflections from shiny magazine and book
paper are so softened that they are neither annoying
nor do they appreciably interfere with vision. These
parallel cases definitely indicate that the size of the light
source is of first importance, if soft and comfortable
lighting is to be obtained.

In direct contrast to this condition let us again place
ourselves out on the country road on a day with a clear

LIGHT IN THE HOME

FIG. 1. — The sun on a clear day, limited in area with respect to the total
sky area, contributes 80 per cent or more of the light on the earth's surface.
Harsh shadows result and eye comfort is reduced.

FUNDAMENTALS OF LIGHTING

FIG. 2. — The overcast sky, extensive in area as a light source, provides great
softness of shadow and eye comfort.

LIGHT IN THE HOME

FIG. 3. — Illumination provided with unshaded lamp bulbs results in harsh
shadows and impaired eye comfort. The size of the principal light source
(the unshaded lamp bulbs) is too small.

FUNDAMENTALS OF LIGHTING

FIG. 4. — Illumination provided from an extended light source, the ceiling,
similarly found out of doors on an overcast day, provides softness of shadow
and eye comfort.

16 LIGHT IN THE HOME

blue sky and full sun. This time we find a very harsh,
clearly defined shadow of ourselves cast on the road.
While this condition may be cheerful, we eventually
find it trying on the eyes, and unless the sun is behind us
we feel vastly relieved when wearing sun glasses. Under
this condition the sun directly contributes four to five
times the amount of light on the surface of the earth that
the entire sky contributes. The sun occupies but a very
small part of the total area of the sky, and the effect of
having such a large part of the light coming from a
relatively small source results in sharp shadows and may
produce an uncomfortable lighting condition. This
condition is readily simulated indoors by hanging a
single bare lamp from the center of the ceiling in a room.
In this case we again find harsh shadows and also an
uncomfortably lighted room. White walls and ceiling
in a room so lighted assist in softening the effect, but just
as the sun out of doors contributed a considerably larger
part of the light falling on any object near the earth
than the sky did, the sky cannot wipe out the harshness
of shadow or the eye discomfort. Similarly, indoors
the white walls and ceiling cannot wipe out the harshness
of shadow or the eye discomfort. When we try to read
print on shiny magazine or book paper under this lighting
condition, annoying reflections of the small source of
light, the bare lamp, are present unless we orient ourselves
and the book to avoid these reflections. Aside from the
harshness and eye discomfort found in interiors illumi-
nated with bare lamps, there is always a feeling of
garishness.

The importance of the size or extent of light-giving
area in an interior cannot be overemphasized. Being
tangible it is easily visualized, and inasmuch as it is
always apparent, predictions or appraisals of the lighting
satisfactoriness may be readily made in a planned or
existing room respectively.

FUNDAMENTALS OF LIGHTING 17

Position of Light Source.

Next in order, but still involved with the size of source,
we turn our^attention to the position of the source of
light. The sun when it is directly overhead at noon is in
its most favorable position for eye comfort, whereas later
in the afternoon its lower position may become extremely
annoying. This experience we most markedly feel when
we have an afternoon of driving to do " against" the
sun. The nearer the horizon or the closer to our line of
vision the light source the more trying the lighting
condition becomes. Carrying the illustration still fur-
ther, bright sunlight on a field of snow is most unpleasant,
for our eyes no longer receive the protection of our fore-
head. The brightly lighted snow has considerable
extent or area which should assist in providing comfort,
but its position (that of being beneath us) plays a large
part in making it uncomfortable to view. Another
factor in this case is the actual brightness of the snow, for
it may be considerably brighter than the sky. Physi-
cally, human beings are not constructed for higher values
of light from below.

Indoors the position of lighting equipment and the
need for controlling the brightnesses of this equipment
should be governed by the experiences obtained out of
doors. Wall brackets, due to their closeness to our line
of vision, should be of low brightness. With the more
conventional candle and similar types of brackets, shades
should always be used to assure low brightness. We
feel more comfortable wearing sun glasses when driving
against the sun. Indoors instead of placing these
glasses on our eyes, we place them on the brackets, and
improvement in effect results.

Lighting Fundamentals Applied.

After considering the extent (area) and positioning of
lighted wall and ceiling areas of the room, we next apply

18 LIGHT IN THE HOME

these same principles to the lighting equipment itself—
ceiling fixtures, wall brackets, and portable lamps. The
more extensive the lighted surfaces of lighting fixtures,
assuming that these surfaces are of material sufficiently
diffusing to conceal the lamp bulbs, the lower will be the
brightness of these areas and, due to the more extensive
surface, the less harsh are the shadows. The limited
surface areas of bare lamps are inadequate for producing
comfortable brightnesses and freedom from harsh shad-
ows. In rooms having darker finishes it is extremely
important that the light-giving surfaces of the fixtures
be low in brightness and as extensive as possible, for
while the dark surfaces of the room reflect light, it is
difficult to make them bright enough, due to their poor
reflecting qualities, to be valuable in affording the " sky-
area" effect which is the softening factor. Light-colored
linings in portable lamps are of great value both from the
point of efficiency of the portable lamp and from that of
the lighting results obtained. The bare lamp inside a
shade having a dark inner surface provides harsh lighting
beneath it, for most of the light is coming from the bulb
itself and relatively little from the inner surface of the
shade. This condition may be thought of as being simi-
lar to the sun without the softening aid of the surrounding
sky areas. Lighten the inner surface of the shade and the
effect of the softening sky area is added; at the same time
a greater amount of light will be given off by the lamp
and shade combination.

Overhead lighting equipment may create effects rang-
ing from harsh, non-uniform downward light from small
light-source areas to highly diffused, soft, practically
shadowless lighting. The latter, due to its high degree
of uniformity and shadowless character, is apt to be
lifeless, monotonous, and lacking in interest and sparkle,
yet its eye-comfort qualities are not to be overlooked.
The former, due to its excessive contrasts and harshness,
can possess great sparkle and interest, yet when depended

FUNDAMENTALS OF LIGHTING 19

upon for visual work has many shortcomings. These
opposite attributes of the two extremes definitely point
to the desirability of combining modified forms of each
of these types of lighting, thereby gaining the advantages
of each and at the same time largely eliminating such
disadvantages as either possesses when used alone.
This can be done in a variety of ways, and it is this lati-
tude in effect that makes it possible to produce individ-
uality in the lighting of various rooms of the home and
also in varying the character of entire homes. A central
fixture can supply the softening (sky area) effect if it
reflects light to the ceiling. Portable lamps containing
reflecting bowls can provide this component, and the
more usual open-top shades on portable lamps can assist in
accomplishing this result. Smaller apparent light-source
areas may be a part of the fixture, bracket, or portable
lamp to furnish the interest element of the lighting.

Reflection and Reflection Factors.

The ease or difficulty of lighting interiors is in a large
measure dependent upon the reflecting qualities of the
walls and particularly the ceiling. White paints and
wall papers are now obtainable which reflect more than
80 per cent of the light striking them. Rooms finished
with such surfaces are easily lighted inasmuch as the
backgrounds for lighting devices are so easily made
luminous, and hence excessive contrasts are avoided. In
such cases a large part of the light striking extremely light
surfaces is reflected, making it simple to provide large-
area sources of softening light. The use of such white-
ness does, however, often introduce coldness and
unpleasantness in an interior and is confined largely to
bathrooms, kitchens, and basements. It is not difficult
to find individuals whose sensibilities are offended by
the use of this extreme whiteness, which is therefore
rapidly coming into disfavor even in these rooms. Light
ivories, buffs, greens, blues, pinks, and warm grays can

20 LIGHT IN THE HOME

be obtained which reflect 60 to 70 per cent of the light
which strikes them, and slightly darker tones of these
colors can be obtained which reflect 50 per cent of the
light striking them. This range of values is both
practical and economical for wall use, although wall
coverings which go as low as 50 per cent will often be
found to be too dark to be pleasing.

Paneled walls of oak, walnut, mahogany, and other
woods, which are finished in the usual rich, dark manner,
are very poor reflectors of light, and accordingly rooms
paneled with these woods are more difficult to light
comfortably than lighter-walled rooms. If, however,
the ceilings of such rooms are left light in color, the prob-
lem is simplified, for much of the light for illuminating
the room can be first directed against the ceiling to
obtain extensive light-source area. When, however, the
ceiling is beamed and the wood or plaster surfaces of the
ceiling are dark, which is so often the case, the softening
effect of light coming from the ceiling and walls cannot be
economically created, and from the decorative point of
view it is not usually desirable. The principal amounts
of useful light will then have to come directly from the
fixtures and lamps. Since the lighting equipment
receives so little assistance from walls and ceiling in
rooms of this character, the shades, reflectors, and other
apparent light-giving surfaces of the fixtures should be
lower in brightness and more extensive in area than simi-
lar parts for rooms finished in the more usual light-colored
walls and ceiling. Shades on portable lamps should also
be denser than those used in lighter-colored rooms, for the
lighter shades and particularly the lightest shades create
undesirable contrasts with the backgrounds (the dark
wall areas) against which they are viewed.

Quantity of Light versus Glare.

If in planning interiors the foregoing principles are
incorporated, the lighting will be usually free from that

Reflection Factors

The proportion of light reflected by walls and ceilings of various colors, that
is, their reflection factors, has an important bearing on both the natural and
the artificial lighting. The proportion reflected will depend somewhat upon the

No. 1

White
Paper
80%

No. 9

Ivory

White

80%

No. 2
Gray

70%

No. 10

Caen
Stone

78%

No. 3

Gray
60%

No. 11

Ivory

77%

No. 7

Gray

28%

No. 8

Gray
19%

No. 12
Ivory
Tan
63%

No. 13

Primrose

68%

No. 14

Lichen

Gray

63%

No. 15

Pearl

Gray

72%

No. 16
Silver Gray
and Caen
Stone

52%

of Colored Surfaces

color of the incident light. The figures here given show what proportion of
the light of tungsten-filament incandescent lamps these painted surfaces reflect.
The reflection factor of any colored surface can be approximated by comparing
it with these samples.

No. 17

Buff Stone
and Pale
Azure
39%

No. 18

Buff

64%

No. 19
Buff Stone
41%

No. 20
Tan

35%

No. 21

Cocoanut

Brown

19%

No. 22

Satin

Green

56%

No. 23
Bright Sage
and Ivory
Tan

48%

No. 24
Bright Sage
41%

No. 25

Forest

Green

20%

No. 26

Olive

Green

21%

No. 27

Pale Azure
and White

55%

No. 28
Pale Azure
40%

No. 29
Sky Blue

37%

No. 30
Shell Pink

54%

No. 31

Pink

52%

No. 32
Cardinal
Red
20%

S1712 S31 534

FUNDAMENTALS OF LIGHTING 21

demon of lighting — glare. We have, however, still one
more factor to consider — amounts of light. Artificial
lighting has long had the stigma of "too much light"
associated with it. This is most unfortunate, for both
physiologically and economically too much light is difficult
to attain, but it is, however, so easy to produce glare
that practically every case of so-called "too much light"
is really a case of glare.

When 23 out of every 100 persons under twenty years
of age have defective vision; when 39 out of every 100
under thirty years of age have defective vision; when
48 out of every 100 under forty years of age and when
82 out of every 100 under sixty years of age have defec-
tive vision, it is not unreasonable to assume that there
must be something wrong with much of our artificial
lighting. True, we have imposed tremendously greater
tasks on our eyes with each step ahead in our civilized
world, but that should warn us to provide better and
better lighting to compensate for the gradually increasing
eye work. Every function of vision which has ever been
tested has always shown improvement with increasing
amounts of light, whether it be speed of reading, accuracy
of vision, sharpness of vision, or any one of the many
phases of vision. These researches definitely point to the
desirability of using intensities of illumination consider-
ably higher than those commonly now in use.
i While it is difficult to assign fixed values of illumina-
tion intensities for the various rooms of the home, due
to the wide variety of decorative schemes which may be
created, suitable equipment for the many services
involved provides a means of obtaining satisfactory
illumination intensities in the majority of cases. Inas-
much as lamp sizes and fixtures, portable lamps, and their
various uses are so closely connected, it is best to consider
these elements together. Since Chapter VIII discusses
these elements in a correlated way, the sizes of lamps
(bulbs) are not discussed in detail in this chapter.

CHAPTER III
CHARACTERISTICS OF INCANDESCENT LAMPS

Incandescence.

A material becomes incandescent when it is heated to a
high temperature. A piece of metal held in a forge until
it is glowing is an incandescent light source of very
elementary form. The hotter a given metal the more
light it emits. The glow from this metal after it is with-
drawn from the fire will furnish light as long as the metal
remains sufficiently hot.

Heat is produced when an electric current flows
through a wire, and it is possible to heat the wire to the
point of incandescence in this way thereby producing
light. As long as the current continues to flow, heat and
light will be produced. For example, if a piece of fine
copper wire were connected between the terminals of an
ordinary dry cell and the length of the connecting wire
gradually shortened, the wire would begin to glow. If
the wire were shortened still more or the number of cells
increased, thereby increasing the voltage, the glow
would become brighter. If this process were continued,
the wire would burn and eventually be destroyed, for
even metals will burn when heated to high temperatures
in the presence of oxygen. For this reason, the filaments
of incandescent lamps are operated always either in a
vacuum or in an inert gas. In general, as the tempera-
ture of an incandescent solid increases, the amount of light
it gives increases, and the color of the light grows whiter.

So-called " white" light is made up of all of the wave
lengths of the visible spectrum in approximately the
proportions found in sunlight or daylight. The charac-

CHARACTERISTICS OF INCANDESCENT LAMPS 23

teristic color of any particular light is determined by the
proportions of different colors of light (wave lengths)
present in its composition. Blue light is made up largely
of short wave lengths, and red light contains a predomi-
nance of long wave lengths. Incandescent lamps pro-
duce a greater amount 'of radiant energy at the longer
wave lengths toward the red end of the spectrum than at
the shorter wave lengths toward the violet end. With
higher filament temperatures the energy distribution is
more even, and the light, therefore, is "whiter." Day-
light, however, is by no means constant in color value,
ranging from clear blue sky through cloud light, to noon
sunlight, and on to late afternoon sunlight. The present
method of obtaining artificial daylight is by filtering out
the excess red light of the incandescent lamps with blue
glass. Such lamps approximate the color of late after-
noon sunlight and are an approach to daylight.

Efficiency.

The relation between light output and the energy used
is known as the efficiency of the lamp and is expressed in
lumens per watt. (When one lumen of light falls on one
square foot of area, an illumination of one foot-candle is
produced on the surface.)

The efficiency of a lamp increases with the tempera-
ture. Therefore, it is desirable to operate the filament
at as high a temperature as possible without melting it.
The filament, however, vaporizes at temperatures below
the melting point, and the lower the temperature the
lower the rate of vaporization. The filament becomes
thinner as its surface evaporates until it finally burns
out. Thus, the higher the temperature the shorter the
life of the filament, so the operating temperature must be
considerably below the melting point in order to gain a
reasonable length of life for the filament.

The selection of a suitable material for filaments was
one of the first difficulties which faced the early lamp

24 LIGHT IN THE HOME

makers. Edison, like other experimenters, tried hun-
dreds of materials before he found a practical method
of carbonization which enabled him to produce the
carbon filament used in his first successful incandescent
lamp (1879). The very high melting point of carbon
recommended it for filament use. The efficiency of the
early carbon lamp was 1.4 lumens per watt.

The development of the osmium and tantalum lamps
marked the first successful attempt to use a metal fila-
ment. These could be operated at higher temperatures
than the carbon lamp and were, therefore, more efficient.
The efficiency of the tantalum lamp in 1906 was approxi-
mately 5 lumens per watt.

In 1907 tungsten lamps were commercially introduced.
Tungsten is particularly suitable for incandescent lamp
filaments because it has a very high melting point — more
than 3000°C. — and does not vaporize so fast as carbon.
Hence, tungsten filaments can be operated at much higher
temperatures than carbon lamps and at, therefore, greater
efficiencies. Each of the steps ahead in these develop-
ments resulted in a higher efficiency as evidenced by the
fact that the drawn-tungsten wire lamps of 1913 operated
at an efficiency of practically 10 lumens per watt or
nearly seven times the light per unit of energy that was
derived from the first incandescent lamp of 1879.

Vacuum and Gas-filled Lamps.

If the air in the lamp bulb were not removed, the oxy-
gen present would combine chemically with the hot
tungsten filament, producing a white smoke and burning
out the filament immediately. The presence of white
powder in a lamp is an indication that some air has
leaked into the bulb, usually through a crack in the glass.

By filling the bulb with an inert gas which will not
combine chemically with the hot filament, the rate at
which the filament material vaporizes may be retarded
and the efficiency of the lamp increased, since the fila-

CHARACTERISTICS OF INCANDESCENT LAMPS 25

ment may be operated at a higher temperature without
shortening its life. The higher operating temperature
of the gas-filled lamps provides a light more nearly white.
Today most incandescent lamps of 40 watts or more
are gas filled. In these lamps, the gas, when heated by
the filament, rises to the upper part of the bulb where it
becomes cooled. It then descends, the cycle being
repeated, so that the gas circulates in the bulb as long as
the lamp is lighted. In rising, the gas carries with it the
particles of tungsten which are evaporating from the
filament and deposits these particles on whatever, part
of the bulb is uppermost. This results in the blackening,
due to filament evaporation, being confined to one area,
thus cutting off less of the light than in the vacuum
lamp where the blackening is more evenly distributed
over the entire inside of the bulb.

Shapes and Sizes of Bulbs.

i am v**'

The various shapes and sizes of lamp bulbs are indi-
cated by a letter and a number. The letter identifies

FIG. 5. — Lamp bulb shapes and their designations.

the shape of the bulb and the number shows its diameter
in eighths of an inch. The A-21 bulb, for example, is
the A shape and is 2>£ or 2^ inches in diameter.

The lamps generally used in home lighting are of the A
shape and are frosted on the inside. Bulbs of the A
shape may be obtained in sizes from 15 to 100 watts;

26 LIGHT IN THE HOME

G (round), F (flame shaped), and T (tubular) bulbs are
used for various decorative applications.

Bases.

The bases of the usual lamps used in home lighting
may be grouped as medium, intermediate, and candelabra
screw bases. The candelabra and the intermediate bases
are used generally for small decorative lamps, while the
medium screw base is used on lamps for general lighting.
The mogul screw base is used on lamps over 200 watts in
size. Some of the indirect-lighting floor lamps employ
the mogul-type base.

FIG. 6. — Lamp bases (actual size). 1. Medium screw base. 2. Intermediate
screw base. 3. Candelabra screw base. 4. Miniature screw base.

A fifth type of base, the miniature screw, is used only
on the low-voltage lamps for flashlights and series-burn-
ing lamps for Christmas-tree strings.

Frosting.

Frosted lamps are preferable to clear lamps, as the
frosting assists in shielding the eyes from the intense
brightness of the filament itself. The resulting illumina-
tion is softened and the shadows cast by the fixture
parts — shade, frames, etc. — are less marked. The inside
frosting, used today in most lamps for general lighting,
absorbs but a small amount of light, less than 1 per cent.
This very small loss is more than compensated for by the
improved lighting obtained.

CHARACTERISTICS OF INCANDESCENT LAMPS 27

Daylight Lamps.

The " daylight" lamp has a bulb of greenish-blue glass
which screens out some of the excess red and yellow rays
in the light emitted by the filament, making the resulting
light which passes through the bulb a practical and
economic daylight approximation.

Life.

i"""""

A lamp may be designed for any average life desired,
but long life is obtained at a sacrifice of efficiency. Two
major items in the cost of light are the cost of energy
and the cost of lamp renewals. Long-lived lamps, being
relatively inefficient, will make the energy cost high for a
given amount of light but will reduce the lamp renewal
cost during a given period. Short-lived lamps, while
reducing the energy cost, will increase the lamp renewal
cost. Theoretically, therefore, the most economical
life is where the sum of these two costs, for a given amount
of light, is a minimum.

All lamps are designed for a certain average life,
depending upon the uses to which they will be put. The
standard general lighting lamps in the A bulb are rated
at 1,000 hours' average life; the decorative G-bulb
lamps at 750 hours, and the F-bulb, 1 amp. at 600 hours.

It should not be expected that every lamp will burn
exactly its rated life, for lamps are like people — some
will live longer than others. The average of any con-
siderable number of lamps, however, produces results
close to the rated life.

Voltage.

Lamps are designed to give the best performance at
specific voltages, such as 110, 115, or 120 volts. The
voltage for any community may be determined from the
lighting company. Everyone knows that the perform-
ance of an automobile tire is affected by inflation above

28 LIGHT IN THE HOME

or below normal pressure. Incorrect voltage acts
similarly on incandescent lamps. A 110- volt lamp
burned on a 11 5- volt circuit produces more light and is
brighter than when it is burned on a 110- volt circuit, but
only about 58 per cent of the normal life of the lamp is
obtained. Vice versa, a 120- volt lamp used on a 115- volt
circuit will burn longer — about 60 per cent — but only
about 86 per cent of its normal light or brightness will be
produced. Longer life can be obtained only at the cost
of poor economy. Lamps should be burned always at
their rated voltage and, therefore, should be selected
with the same voltage rating as the circuit on which they
are to operate.

Carbon Lamps.

The so-called 16-candlepower carbon lamp consumes
slightly more than 60 watts of energy but it provides only
one-third the light produced by one of the modern gas-
filled tungsten-filament 60-watt lamps. Judging from
the great number of carbon lamps in use today, the low
efficiency of the carbon lamp is not universally appre-
ciated. The amount of energy wasted in burning a car-
bon lamp 1,000 hours — the average life of the modern
gas-filled lamp — equals in cost one dozen modern gas-
filled tungsten-filament lamps. It is not uncommon to
find people appraising the quality of incandescent lamps
only in terms of the number of years that a lamp has
continued to burn. Light, rather than electricity or
lamps, is really the commodity being purchased. The
modern gas-filled tungsten-filament lamp affords the
greatest amount of light for a given expenditure.

Summary.

An incandescent lamp is essentially a filament of some
material that is able to withstand high temperatures
without too rapid vaporization. It gives light by virtue
of its being heated to incandescence by the passage of

CHARACTERISTICS OF INCANDESCENT LAMPS

TABLE I. — PRINCIPAL APPLICATIONS OF LAMPS USED IN

RESIDENCE LIGHTING
(Shapes and Finishes as of August 14, 1931)

Watts

Bulb

Base

Finish

Application

A-17

Medium

Inside frosted

Decorative lamps and wall
brackets

A-19

Medium

Inside frosted or
ivory

Decorative wall brackets and
wall pockets

A- 19

Medium

Flame tint, ivory
or old rose

Decorative lighting effects

A-19

Medium

Inside frosted or
ivory

Ceiling fixtures, wall brackets,
and portable lamps

A-19

Medium

Flame tint, ivory
or old rose

Decorative lighting effects

A-21

Medium

Inside frosted

Ceiling fixtures, utility brackets,
and portable lamps

100

A-23

Medium

Inside frosted

Ceiling fixtures and portable
lamps

150

PS-25

Medium

Inside frosted

Enclosing globes and semi-indi-
rect ceiling fixtures

200

PS-30

Medium

Inside frosted

Indirect ceiling fixtures and
lamps

300

PS-35

Medium

Inside frosted

Indirect ceiling fixtures and
lamps

A-21

Medium

Daylight

Bathrooms, laundries, kitchens,
and sewing rooms (for local
applications)

100

A-23

Medium

Daylight

Bathrooms, laundries, kitchen,
and sewing-room ceiling fixtures

150

PS-25

Medium

Daylight

Bathrooms, laundries, kitchen,
and sewing room ceiling fixtures

S-6

Candelabra

Clear

Light ornaments and pilot lights

S-ll

Intermediate

White, flame tint,
and colored

Decorative lamps, light orna-
ments, and coves

G-16M

Intermediate or
candelabra

White or flame
tint

Decorative wall brackets and
lamps

F-10

Intermediate or
candelabra

White or flame
tint

Decorative wall brackets and
lamps

F-15

Medium

Flame tint or
white

Decorative wall brackets and
lamps

G-18>£

Medium

Flame tint or
white

Decorative wall brackets and
lamps

G-25

Medium

Flame tint or
white

Decorative fixtures and wall
brackets

G-25

Medium

Flame tint or
white

Decorative fixtures and wall
brackets

T-6K

Intermediate

Clear

Modernistic wall brackets,
special fixtures, and coves

30 LIGHT IN THE HOME

an electric current through it. To prevent the filament
from oxidizing or burning up, it is operated either in a
vacuum or in an atmosphere of inert gas. In a vacuum,
the filament suffers by reason of the absence of a pressure
to assist counteracting the tendency to vaporize. This
difficulty is overcome in the gas-filled lamps by the use
of an inert gas in the bulb which permits operating the
filament at a higher temperature with a less rapid rate of
vaporization.

CHAPTER IV
LIGHT AND COLOR

Spectral Composition of Light.

Light is the master painter and sculptor, for light
colors and models everything. Obviously, without light
our eyes would be of no value, and the presence and shape
of objects would have to be detected largely by touch;
color would not exist, for without light all things are
black. It is light which possesses the color and not the
objects. Nature reveals the fact that sunlight, which
we may call a " white light," is a "mixture" of a great
many colored lights when she exhibits her marvelous
display — the rainbow. The raindrops in the air reflect
the light of the sun back to us during this phenomenon
and while doing this they also break the white light into
its component parts, and we readily see these parts as
red, orange, yellow, green, blue, and violet lights strung
in bands of color. These colors are called spectral
colors. The rainbow provides us with conclusive proof
that white light is made up of all the spectral colors.

Without some optical device such as the raindrop,
prism, or finely ruled lines on glass (a grating) it is doubt-
ful if we would be permitted to see the color composition
of light. Our eyes are not analytical. They see only
the summed-up effect of light mixtures. They do not in
themselves break these mixtures into their component
parts.

When we view an object, we usually see this object
by the light which is reflected from it to our eyes. If
the surface viewed is painted white, practically all of the
light striking it is reflected. If it is painted medium

32 LIGHT IN THE HOME

gray, one-half of the light'may be absorbed by the surface,
and the remaining one-half reflected. When we view, a
surface painted black, as much as 90 per cent or more of
the light striking it may be absorbed, leaving only a
small amount to be reflected to the eye. Surfaces
painted white, medium gray, and black, placed alongside
of each other and illuminated with the same amount of
light, appear white, medium gray, and black, respec-
tively, because they absorb different amounts of light.

The entire absence of light or the condition of no light
is perfect black. A room with tight-fitting, opaque
curtains becomes black the moment the light with which
it is illuminated is extinguished. All surfaces absorb
some light; even the very lightest surfaces exhibit this
characteristic.

White light or any given composition of colored light
can be considered as a mixture in which very definite
amounts of each of the spectral colors involved are
present. Change the amount of any of the l ' ingredients' '
in such mixtures and the color of the resulting light will
be changed. For example, we can consider white light
as a mixture in which practically equal amounts of each
color are present; reduce the amount of blue present but
slightly, and the white light becomes yellowish; reduce the
red component but slightly, and the white light becomes
bluish; reduce the green slightly, and the resulting light
will be purplish. On the other hand, if all colors present
are reduced equally in amount, the color of resulting
light is not changed. A neutral gray (a gray which
exhibits no colorfulness) is gray and not colored, because
it absorbs equally all the colors in white light which
strikes it.

Pigments.

Surfaces which appear colored under white light
possess in themselves the ability to absorb some colors
and reflect others. The pigment on the surface can be

LIGHT AND COLOR 33

thought of as having " likes" and " dislikes," and further-
more, except for fading, a given pigment or a mixture of
pigments will always exhibit the same likes and dislikes.
In the case of a surface which appears red under white
light, the surface likes (absorbs) the blue, green, and
yellow components of the white light striking it, but it
does not like red, it " rejects " (reflects) the red component
of the white light to our eyes, and the sensation is exactly
the same as though red light were entering the eye from
a primary light source.

In viewing a card which appears blue, the pigment
absorbs the red, yellow, and green components of the
white light, and only the blue is left to be reflected, and
accordingly only blue is reflected to our eyes. Green
pigment absorbs all colors but green; yellow pigment
absorbs all colors but yellow; and so on. Actually few
pigments possess the ability completely to absorb all
colors but one. The red pigment readily absorbs all the
colors but red. It does not, usually, completely absorb
orange; hence there will be some orange reflected with
the red. The green pigment may completely reflect
green light, but it does not completely absorb blue and
yellow, and accordingly both blue and yellow will be
partly reflected with the green. If a considerable amount
of blue is reflected with the green, the result is a bluish
green; whereas if considerable yellow is reflected with
the green, the result is a yellowish green. From this it is
seen that the purity of color reflected depends upon the
ability of the pigment to absorb color. When all colors
but one are absorbed, very high purity of the color
reflected may result.

Pigment Mixtures.

The colors resulting from the mixing of pigments
involve the same physical processes as just discussed. A
mixture of yellow and blue pigments produces green.
The yellow pigment is one that does not absorb every-

34 LIGHT IN THE HOME

thing but yellow. In fact it also reflects green. The
blue pigment will, of course, reflect blue, but inasmuch
as the yellow pigment with which it is mixed absorbs
practically all the blue, there will be little or no blue
reflected. Therefore, the blue used reflects green, and
inasmuch as the yellow pigment reflects green, they
both reflect green. Thus far we have only green reflected.
The yellow pigment of the mixture reflects yellow,
but the blue does not; hence the blue will suppress the
yellow. Finally, we see that green is the only color which
is reflected in common by both elements of the mixture,
and the surface so coated appears green. Colors result-
ing from mixtures of pigments always take on their
apparent colors in accordance with the principles just
described.

Colored Light.

Thus far we have dealt with light reflected from
surfaces coated with some form of pigmentation. A
discussion of color would not be complete without
dealing with mixtures of lights of various colors directly
from light sources. Colored light may be produced
by interposing a " colored" transmitting medium (dyed
fabric or gelatin and colored glass) between the light
source and the surface to be illuminated. These materi-
als possess the ability to absorb light of certain colors
and to transmit others. The color or colors transmitted
produce a definite color to the transmitted light. For
example, a so-called "red" piece of silk or gelatin
may have any color of light fall upon it but only red
light will be freely transmitted through it. Accord-
ingly when white light, which is composed of all the
spectral colors, falls on the silk or gelatin, it will freely
transmit only the red component of the white light,
and the resulting transmitted light is red. Due to
the vast numbers of dyes and their mixtures it is possi-
ble to obtain a vast variety of colored lights in this

LIGHT AND COLOR 35

manner. Colored glass also occupies an important
position in this field, although the variety of available
colors is more limited. Pigments on glass are also used
to produce colored light, although their use is limited
chiefly to incandescent-lamp bulb coatings placed either
on the outside or on the inside of the bulbs. In this
case light striking the small pigment particles is altered
in color by absorption. Only a very small part of the
resulting light actually passes through the pigment
particles, for most of it is reflected from the surface
of the pigment particles; and inasmuch as there are
spaces between the particles, the emerging light after
striking the pigment particles escapes through these
minute spaces.

Colored-light Mixtures.

After the consideration of a single light source with
a given color medium for producing colored light, we
may consider the lighting of surfaces with several light
sources, each equipped with a different color medium,
to produce a vast variety of desired colors of the surface
so illuminated. This variety of color can be obtained
from three light sources and three properly chosen color
media. The light sources used, however, must illumi-
nate the same given surface. The colors used are red,
green, and blue, and they are called the additive pri-
maries. When used to illuminate a white surface,
various quantitative mixtures of red and blue light can
produce an extensive series of purples, ranging from
reddish purple through mid-purple to a blue-purple.
Mixtures of red and green produce yellows, ranging
from pinkish yellow to greenish yellow. Some of the
colors produced in this series are known as the ambers.
Mixtures of blue and green produce a series of colors
ranging from blue-green up to mixtures which are diffi-
cult to name as either blue or green on through to green-
blue. In each case the various colors of a series are

36 LIGHT IN THE HOME

produced by using varying proportions of the two colors.
A large amount of blue with a small amount of red
produces a bluish purple, while a large amount of Ted
with a lesser amount of blue produces a reddish purple.
While it is not particularly practicable to produce
white light with mixtures of red, green, and blue lights,
the proper proportions of these three primaries used
together do produce white light.

Additive and Subtractive Primaries.

It should be noted that these three primary colors
(red, green, blue) are not the same primary colors
used by the artist in dealing with pigments. The
pigment primaries are usually named red, yellow, and
blue. If, however, the artist had to produce all of
his work from three pigment colors, it would be found
that the pigment primaries would be more accurately
described as a reddish purple, yellow, and blue-green.
While it may appear that these two differing sets of prima-
ries present an inconsistent situation, nothing could be
further from the truth. There is the closest of relation-
ships between the two. We do, however, have to bear
in mind that for a surface to be colored with the "light"
primaries, one or more of these primaries must fall
upon a white surface to produce the possible range
of colors with these primaries, while all the colors in
white light must fall on a pigment-covered surface
in order that the surface may select out of the entire
assortment the color it always absorbs and in turn
reflect that color or those colors which it always reflects.
Colors of the first set are always added either in space
or at the surface to be colored; while with the second
set (the pigments), white light — a composition of all
the colors — must fall on these pigments in order that
subtraction may take place. As previously stated,
the " light" primaries (red, green, blue) are termed
the additive primaries, and the " pigment" primaries

Fig. 7. — The subtractive method of mixing colors. The result
obtained when mixing pigments.

Fig. 8. — The additive method of mixing colors. The result
obtained when mixing colored lights.

From " Color and Its Application " by M. Luckiesh.

By permission of the D. Van Nostrand Company, Inc., New York, N.Y.

LIGHT AND COLOR 37

(reddish purple, yellow, blue-green) are termed the
subtractive primaries. When the action which is taking
place on the surface illuminated (namely, the addi-
tion of colored light to produce the color and the sub-
traction of lights of certain colors at the surface to
produce a resultant color), the significance of the terms
1 ' additive ' ' and ' i subtractive' ' primaries becomes obvious.

TABLE II. — ADDITIVE AND SUBTRACTIVE PRIMARY
COMBINATIONS

Additive Primary Combi- Subtractive Primary Combi-
nations (Light Mixtures) nations (Pigment Mixtures)
Red + blue = reddish purple Reddish purple + yellow =

red

Green + red = yellow Yellow + blue-green = green

Blue + green = blue-green Blue-green + reddish purple

= blue

The close relationship between the two sets of pri-
maries is verified when we allow red and blue light to
fall on a white surface, for this pair produces reddish
purple, one of the pigment primaries. Again, when
we allow green and red light to fall on a white surface,
yellow light results, another one of the three pigment
primaries. Last allow blue and green light to fall on
a white surface, and a blue-green results, the third of
the pigment primaries. Furthermore, any two of the
pigment primaries may be mixed together in proper
amounts to produce one of the light primaries. Reddish
purple and yellow pigments mixed produce red, one
of the additive primaries. Yellow and blue-green
pigments mixed produce green, another of the light
primaries; while blue-green and reddish purple pigments
mixed can produce blue, the third of the light primaries.
These relationships are readily demonstrated with the
proper choice of pigments and light filters. In checking
these combinations it becomes apparent that it is all
readily understood with the exception of the addition

38 LIGHT IN THE HOME

of the red and green light which produce yellow light.
In this case yellow need not be present in either the red
or the green light used to produce the sensation of yellow
light. Actually the yellow sensation is produced when
the eye is stimulated by red and green light. This
method of producing a yellow may be thought of as a
synthetic one, for pure yellow light entering the eye
also creates the sensation of yellow.

Apparent Color Changes.

Some of the peculiarities and attributes of color are
invaluable in making an intelligent use of it. For
example, colors appear less colorful when viewed under
high illumination or at high brightnesses. The artist
will paint a deep-red object which is illuminated by
direct sunlight of high intensity, orange-red instead
of red, because the high-intensity illumination on the
deep-red object robs this object of its deep colorfulness.
View this same object in the shade, and it will take
on its full colorfulness.

The extent of a given area of color plays an important
role in apparent color. Researches indicate that larger
areas of a given color appear more colorful than smaller
areas.

Time of exposure apparently has much to do with
how colorful a color appears. The longer one views
a color the less colorful it appears to be. An hour or
more spent in a red-illuminated photographic dark
room provides excellent proof of this.

When two colors are placed close together — for
example, when red and green are juxtaposed — they
appear accentuated in color and deeper in hue. These
same two colors separated appear, however, very much
the same as though they were viewed separately. Sur-
rounding a relatively small area of a given color by
another color often produces very striking changes
in the color of the smaller area. A black pattern on a

LIGHT AND COLOR

red ground may appear blue green; a white surrounded
by green will appear brighter and of a pinkish tint.

TABLE III. — SOME APPARENT COLOR CHANGES PRODUCED BY

CONTRAST

Color of Smaller Area
Viewed Alone

Color of
Surrounding
Smaller Area

III
Apparent Color of
Smaller Area when
Surrounded by Color
in Column II

Light green

Red

1 Dark green

Light blue

\ Green
[Blue

Red
o

| Brownish yellow
[ Yellow-green

Dark blue

"D 1

Light red . . .

Green
[Blue

Red
r~\

Purple
[Brownish gray

Reddish brown

Green
Blue

Bright red
Orange

These effects are obtained only when the proper
colors are chosen and proper brightness of the colors
employed.

Symbolism of Color.

Association, usage, sensation, all contribute toward
a more or less universal " language of color."1

Red is associated with danger and blood. It is
characteristically a stimulant or excitant.

Yellow or orange is often significant of light and
warmth due to the association of this color with the

^UCKIESH, M., "Language of Color," Dodd, Mead & Company, Inc.
LUCKIESH, M., "Light and Color in Advertising and Merchandising,"
D. Van Nostrand Company.

40 LIGHT IN THE HOME

sun or with sunlight. Yellow and orange are mildly
stimulative and are described as warm colors.

Green is the most conspicuous garb of nature and
thus represents life. It is particularly associated with
freshness and newness of springtime, and from analogy
there have arisen many uses of green symbolizing youth,
immaturity, etc. Green is most generally characterized
as a neutral color, perhaps due to continued adaptation
to large areas of this color in nature. Nature's greens
are darker or deeper in shade than is commonly realized.
Certain greens can be very disagreeable.

Blue, due to its earliest association with the sky
or heaven, took on a divine significance. The darker
blue found toward nightfall, a time of quietude, has
undoubtedly bestowed on this color the attribute of
sedateness. Blue may be serene, cold, sedate, or
depressing, depending upon its tint and hue.

Purple of a hue resulting from mixtures of approxi-
mately equal parts of red and blue lights has long
been a color of state. We know that it was one
of the most costly colors in early history, and this may
account for its use as a regal color.

White is the logical color for symbolizing purity,
innocence, chastity, etc. The purity of freshly fallen
snow brings this to mind again and again. It produces
the extreme of contrast when used with black. It is,
however, coming into some disrepute for interiors, for
it is harsh.

Alack is the antithesis of white, and its association
with gloom and darkness renders it a fitting symbol
for woe and fear. As it provides an environment for
evil deeds, it is emblematic of crime.

Gray is the color of age because the hair of the aged
is hoary gray. This association also results in a signifi-
cation of ripened judgment and maturity. White is
enlivening; black is gloomy; and gray is intermediate,
sad. Colors and their combinations may be agree-

LIGHT AND COLOR 41

able, cheerful, stimulating, neutral, tranquilizing, depress-
ing, warm, cold, stern, stately, weak, or impressive. These
are factors which should always be borne in mind when-
ever color schemes are being evolved.

Use of Colored Light.

In using colored light for illuminating interiors and
objects contained therein, it must be remembered that
distortion of the color of areas and objects so illuminated
is likely to occur. Sometimes the resulting distortion
or change of color is a sought-for effect, whereas in
other cases it may be so disastrous that entire color
schemes must be discarded or the lighting scheme
abandoned. An exact prediction of the appearance
of a color under lights of various colors cannot be made
without an exact knowledge of the reflecting char-
acteristics of the surface illuminated and of the spectral
composition of the light used. If, however, we consider
the use of colored light that would be commercially
termed medium, red, yellow, green, or blue, the changes
in the appearance of colored fabrics, wall surfaces,
and colored objects illuminated by these lamps can be
approximately stated. A number of these predictions
are indicated in Table IV.

In recent years a marked advance in the use of color
in the home has taken place. This is evidenced in
hangings, colorfully painted furniture, dishes, and even
in kitchenware. This prompts the question as to what
we may do with colored light in the home. In fact
discussions of the possibilities of lighting given rooms
with colored light have appeared from time to time.
With the emotive power of colored light in mind, it
would seem that rooms might be fitted with lighting
systems which would bathe an entire room in red, green,
or blue light or resulting mixtures of these colors, thereby
creating a room which could be changed from one of
warmth to one of coolness, or one which would stimulate

LIGHT IN THE HOME

or depress, and so on. Theater auditoriums employ
such systems of lighting, and inasmuch as we go .to
the theater to be entertained and spend but a short
time in them, such systems of lighting are extremely
valuable and appropriate. On the other hand, but

TABLE IV. — RESULTING EFFECTS OF COLORED LIGHT ON THE
APPEARANCE OF OBJECTS

Appearance of Object
under White Light

Color of Light Illuminating Object

Red

Orange

Yellow

Green

Blue

Purple

Black
White

Red
black

Red
Red

Orange
black

Orange
Scarlet

Yellow
black

Yellow
Orange

Green
black

Green
Brown

Blue
black

Blue

Purplish
black

Purple
black

Purple

Reddish
purple

Red

Orange
Yellow

Red

Orange
red

Red

shade

Orange

Yellow

orange

Yellow
green

Yellow
orange

Yellow

Greenish
yellow

Yellowish
green

Green

Black

Greenish
black

Blue
green

Reddish
purple

Yellowish
orange

Brown
black

Light green

Deep green
Light blue

Black
Purple
Purple

Greenish
black

Dark
gray

Blue
gray

Yellowish
green

Yellowish
shade

Gray

Green

Blue
green

Greenish
blue

Blue
Blue

Blue
black

Blue

grayish

Blue

Deep blue

Purple

Red

shade

Red

shade

Red

shade

Blue

black

Blue

Purple

few people can tolerate the use of a general distribution
of pure colored light in the rooms of the home and partic-
ularly over a considerable period of time. This is
not surprising, because the more usual home can scarcely
be expected to permit of highly theatrical treatments.
Delicate tints of generally distributed colored light

LIGHT AND COLOR 43

can, however, be used, particularly for secondary
effects. For example, dining-room fixtures may be
designed which provide several separately controlled
tints of light directed toward the ceiling, while the table
itself is provided with uncolored light from lamps
independent of the tinted lamps. Similarly, the light-
ing from coves in the dining room may be tinted. Since
the dining room is occupied but a short time each day,
its lighting treatment may be considerably more theatri-
cal than that employed in other rooms.

Small, highly colorful spots of light, when judiciously
selected and placed, possess qualities not found with
other decorative media. Colored lamps, used in small,
translucent art objects, purely decorative portable
lamps which may be quite colorful, and restricted spots
of wall area may be illuminated to silhouette art objects,
using appropriate tints or colors of light. The more
subtle and delicate effects are to be preferred in most
cases, and until one's experience has been rounded
out, they are considerably safer and more desirable
to employ.

CHAPTER V
FUNDAMENTALS OF ELECTRICITY

Beginnings of Electricity.

About twenty-five centuries ago, Thales of Miletus,
a Greek philosopher, recorded the fact that amber,
when rubbed, will attract objects. This period of
Thales, about 600 B.C., is generally taken by historians
as the genesis of electrical discovery.

Pliny records that the Syrian women called amber
the "clutcher," from its use in spinning. It is con-
ceivable that the name came down from the old Phoeni-
cians. The distaffs of the wealthy were made of amber,
and when the amber was electrified by rubbing, it
drew to itself such small bits of dust and chaff as might
be near. The color and luster of the amber reminded
the fanciful Greeks of the yellow sunshine. They named
their beautiful amber " electron" from which our word
" electricity " descends.

For two thousand years Thales' original observation
lay dormant and was unproductive. Then toward
the close of the sixteenth century Dr. William Gilbert,
physician to Queen Elizabeth, extended the early
observations and showed that many bodies besides
amber, such as glass, sulphur, tourmaline, etc., possess
the strange property of first attracting, then repelling
bodies brought near them. Gilbert published his obser-
vations in the year 1600 in a book called "De Magnete, "
which is among the very earliest printed records relating
in any way to electricity. He described a large number of
experiments and divided bodies into two great classes-
electrics, or those which could be electrified by friction,

FUNDAMENTALS OF ELECTRICITY

and non-electrics, or those which could not be so
electrified.

A little later Otto von Guericke, philosopher and
burgomaster of the city of Magdeburg, conducted
experiments on the attraction of amber. In order to
save time and labor in rubbing the amber by hand,
he made, in 1650, a machine consisting of a large ball
of sulphur mounted on a shaft which could be rotated.
He found that the electricity generated when the hand
was pressed against the globe as it rotated could be
conducted away by a chain and would appear at the
other end of the chain. Thus the principle was estab-
lished that electric attraction could be " conducted"
and made evident at a point distant from its source.
The transmission of electrical energy was born in this
primitive laboratory at Magdeburg.

Conductors and Insulators.

Some substances will conduct electricity and others
will not. However, there is no sharp line dividing
conductors from non-conductors. (The latter are called
insulators.) Most insulators conduct a small amount
of electricity, and even the good conductors vary greatly
in conductivity. The following table classifies a few
common substances:

TABLE V. — PRINCIPAL CONDUCTING AND INSULATING
SUBSTANCES

Good Conductors

Poor Conductors

Insulators

Aqueous solutions

Alcohol

Amber

of salts and acids

Dry wood

Bakelite

Carbon

Kerosene

Dry air

Gas

Paper

Glass

Graphite

Pure water — —

^Hard rubber

Metals -

Porcelain

Sulphur

46 LIGHT IN THE HOME

Electricity is fundamentally an agency or force in
nature, and through the harnessing of this force accord-
ing to certain established laws, it may be made to pro-
duce heat, light, and power. We know how to measure
electricity and how it will behave under certain
conditions.

Units of Measurement.

In order that water may flow through a pipe, it
is essential to have some driving or motive force such
as the pressure furnished by a pump. Similarly,
electricity will flow along a wire, under the influence
of an electromotive force, such as is furnished by a
battery or a dynamo. The unit of electromotive
force is the volt. A volt may be defined as the electro-
motive force needed to drive a current of one ampere
through a resistance of one ohm.

Electricity flowing along a wire is somewhat analogous
to water flowing through a pipe. The rate of flow of
the water can be measured in cubic feet or gallons per
minute or per second. In much the same way electric-
ity is spoken of as flowing along a wire. Just as the
gallon per minute is a unit expressing flow of water,
so an ampere is a unit expressing flow of electricity.

Although substances may be divided into two classes,
conductors and non-conductors or insulators, even the
best conductors of electricity are not perfect. This
means that all conductors offer some resistance to the
flow of electricity which is manifested by the conversion
of a part of the electrical energy into heat. A stream
of water flowing through a pipe is retarded by the fric-
tion of the pipe. The amount of this friction depends
upon the smoothness of the inner surface, the length,
and the cross-section of the pipe. So with electricity,
the resistance of a conductor depends upon the con-
ductivity of the material used (which varies slightly
with temperature) and upon the length and cross-section

FUNDAMENTALS OF ELECTRICITY 47

of the conductor. The unit of resistance is called the
ohm, which is the amount of resistance through which
an electromotive force or potential of one volt will
force a current of one ampere.

In general, the current increases as the electromotive
force increases, and the current decreases as the resist-
ance in the circuit increases. A German physicist,
Ohm, was the first to state this relation between current,
electromotive force, and resistance. This relation, known
as Ohm's law, may be stated as follows : The rate of flow
of electricity along a conductor equals the electromotive
force divided by the resistance.

In electrical units : Amperes = -r-

In symbols: 7 = T>-

where / is rate of flow of electricity in amperes.

E is electromotive force in volts.
R is resistance in ohms.

Thus, if any two of the above quantities are known,
the third may be calculated.

Circuits.

An electrical circuit is a series of insulated, good
conductors leading from a source of electricity through
some device using electricity and back again to the
source. If a bell is to be operated by an electric battery,
for example, a dry cell, it is so connected that the elec-
tricity passes through it as a part of the circuit. When
this circuit is broken at any point by a switch, key,
or push button, so that no electricity jumps the gap,
the circuit is said to be open. When the switch or key
is closed so that a continuous conducting path is made,
the circuit is said to be closed or made.

LIGHT IN THE HOME

short circuit results when two conductors touch,
forming a continuous low-resistance path back to the
source of supply so that the current is turned from
its intended path and sent back to the source before it
has passed through the current-using device. Such a
condition may exist when flexible cord becomes worn
so that the insulation on the wires is frayed, permitting
the two conductors to touch. Sparking results, and
generally a fuse is blown.

When pieces of electrical equipment such as lamps
or other current-using devices are arranged so that

O
O
O
o
o

FIG. 9. — A series
circuit.

FIG. 10.— A parallel or
multiple circuit.

the current passes through first one, then the second,
and so on in a continuous path back to its source, a
series circuit is said to exist (Fig. 9). An example
of a series circuit is found in the strings of eight Christ-
mas-tree lamps where all of the lamps go out if one
burns out, thus making a break in the circuit through
which the current cannot flow. If these eight lamps
had been so arranged that the circuit was divided among
them instead of going through first one and then the
second, and so on, the circuit would be described as
parallel or multiple. Lamps operated in the home
are usually arranged in parallel circuits (Fig 10).
The laws governing series circuits are:

FUNDAMENTALS OF ELECTRICITY 49

The current (7, amperes) in every part of a series
circuit is the same.

The resistance (R, ohms) of the several resistances
in series (lamps or other current-consuming devices)
is the sum of the separate resistances.

The voltage (E, volts) across several resistances
in series is equal to the sum of the voltages across the
separate resistances.

The laws governing parallel circuits are:

The total current through the combination of resist-
ances is the sum of the currents through the parts.

The voltage across each separate resistance of the
parallel resistances is the same.

Measurement of Power.

To measure electric power it is necessary to know the
quantity of electricity flowing per second (amperes) and
the pressure or voltage. The watt is the unit of electric
power and may be defined as the power required to keep
a current of one ampere flowing under pressure of one
volt. This may be expressed as

W (watts) = E (voltage) X / (current).

In other words, electric power or watts is the product
of volts times amperes.

Since the watt is a very small unit of power, a unit
of 1,000 watts — 1 kilowatt — is usually employed. The
term employs the prefix kilo meaning thousand. The
watt is readily convertible into other units used to
measure power. For example, 1 horsepower equals
746 watts, or 1.34 horsepower equals 1 kilowatt.

Power means the rate of doing work. The total
work done is equal to the product of the rate of doing
work multiplied by the time. If an electric generator
is delivering electricity at the rate of 15 kilowatts for 8
hours, it does 8 times 15, or 120 kilowatt-hours of work.
The consumption as well as the production of electricity

50 LIGHT IN THE HOME

is measured in kilowatt-hours. For example, if ten
50-watt lamps burned for 3 hours, the consumption

. , , 10 X 50 X 3
would be — — . nnrt or 1.5 kilowatt-hours.

1 jUUU

Measurement of the Use of Electricity.

The watt-hour meter is a device used to record the
use of power over a given period. Essentially it is a small
electric motor the number of revolutions of which is
directly proportional to the amount of energy passing
through it. By means of gears, the revolutions are
registered upon a series of dials scaled in kilowatt-
hours. Each dial is graduated into ten divisions,
and each has a pointer which travels around the dial.
The mechanism is so arranged that a complete revolu-
tion of one pointer causes the pointer immediately at
its left to advance one division. Thus, reading from
right to left, one complete revolution of the pointer
of the first dial represents 10 kilowatt-hours; of the
second, 100 kilowatt-hours; of the third, 1,000 kilowatt-
hours; and of the fourth, 10,000 kilowatt-hours.

In the ordinary household meter each division of the
dial on the extreme right represents 1 kilowatt-hour
or 1,000 watt-hours. If a 100-watt lamp were burned
for 10 hours, the pointer on this dial would advance
one division.

The electricity meter operates under more varied
conditions and must do a more exacting task than almost
any other measuring device. It is frequently subjected
to vibration, moisture, and extremes of temperature;
it must register accurately on varying voltages and
loads; it must operate for long periods without any
maintenance or attention. It meets all of these condi-
tions, and it measures the use of electricity with an
extremely high degree of accuracy. The watt-hour
meter is, in fact, one of the most accurate commercial
measuring devices with which we come in contact.

FUNDAMENTALS OF ELECTRICITY 51

Figures 11 and 12 show the dials which indicate, in
Fig. 11:

The first pointer (extreme left hand) between 6
and 7.

The second pointer between 9 and 0.

The third pointer between 3 and 4.

FIG. 11. — The meter registers 6,931 kilowatt-hours.

The fourth pointer (extreme right hand) between
1 and 2.

Taking the lower value in each case, the reading
is 6,931 kilowatt-hours. Taking a second reading
at a later period (Fig. 12), the pointers show 7,123
kilowatt-hours. The difference between the second
reading and the first, or 192 kilowatt-hours, is the energy
consumption registered during the period.

HOURS

FIG. 12. — The meter registers 7,123 kilowatt-hours.

In cases where any pointer is about on a figure and
it is doubtful whether the reading should show that
figure or the one preceding it, the reading may be checked
by the position of the pointer on the next right-hand
dial. For example, if the pointer on the 10,000 dial
(Fig. 11) is directly on the figure 7 and it is uncertain
whether to note the reading 7,931 or 6,931, the reading

52 LIGHT IN THE HOME

may be checked by reference to the pointer on the
1,000 dial. It will be noted that this pointer had passed
the 9 but has not yet passed the zero mark. Therefore,
a complete revolution from zero to zero has not yet
been made and the pointer on the 10,000 dial should
be given the lower reading.

Cost of Operating Lamps and Appliances.

Charges for electric service are based upon the kilowatt-
hour consumption and are stated as so many cents per
kilowatt-hour, which is referred to as the rate. If the rate
is known, it is a simple matter to calculate the cost of
operating lamps or appliances. Each lamp has a watt-
age rating stamped on it, and each appliance carries
a name plate which shows either volts and watts or
volts and amperes. If only the latter are given, the
wattage is obtained easily by using the formula

Watts = volts X amperes.

The cost of operation is obtained by multiplying the
wattage by the hours of use and dividing by 1,000;
then multiplying this quantity by the rate in cents.
The result is the operating cost in cents.

CHAPTER VI
WIRING FOR THE HOME

A well-wired house might be described as one in
which there are outlets equal to the number required
for all present as well as future needs; these outlets
are thoughtfully placed for the uses to which they will
be put; the lighting outlets are conveniently controlled;
adequate circuits are provided; and good materials
are used throughout. To provide such an installa-
tion helps to lay the foundation for convenience, comfort,
satisfaction and beauty in this present electrical age.

Because the wiring is a thing unseen, it usually does
not receive the attention it deserves. Wiring contriv-
ances such as cords for lamps carried for distances around
baseboards, tucked under rugs, fastened over door
frames, and then connected to ceiling and wall-bracket
sockets are commonly seen. There is a decided lack
of wall switches in most homes, making it difficult
to turn on the light when entering a dark room. Such
wiring is a great handicap, yet little concern is given
to correcting it in existing homes or improving it when
building new ones, unless one has lived in a well-wired
home, thereby appreciating the benefits a good wiring
system offers.

Electrical Circuits.

Briefly, electrical circuits may be explained thus:
First, the service entrance is the construction on the
outside of the building, extending from the service
switch, which is usually in the basement, through the
foundation and up to a point some 10 or 12 feet above
the ground. At this point the connection to the power

LIGHT IN THE HOME

METAL.
BOX FOR

WALL
OUTLET

METAU
BOX FOR
CEILING

OUTLET

TUMBLER
SWITCH AND

METAL BOX

FLEXIBLE
CONDUCTORS

CONVENIENCE
OUTLET AND
METAL BOX

BELL

RINGING
TRANSFORMER

SAFETY
DISTRIBUTION
PANEL

SAFETY
ENTRANCE
SWVTCH

CODE
WIRE

FIG. 13. — Electrical parts for house wiring installations.

WIRING FOR THE HOME

FIG. 14. — Entrance safety service switch with door open. Meter mounted

above it.

56 LIGHT IN THE HOME

company's wires is made. The service switch connects
the house wiring to the service entrance. Directly
connected to the service switch is found the meter box,
generally placed in the basement. In some localities,
however, the meter is placed on the outside of the house
or housed in the foundation of the building to assure
easy access for the meter reader. From the meter, the
line is taken to a panel box which usually contains
the fuses. The panel box in the past was frequently
placed in the cellar or attic, but in the newly built homes
it is customary to put it in a more accessible place,
in a back hall closet or even in the kitchen. The panel
box is simply a distributing box from which the main
supply of current is subdivided into branch circuits.
To protect these circuits so that they will not be taxed
in excess of what they are designed to carry, a fuse
is placed at the beginning of each circuit. Each circuit
should be plainly marked so as to indicate the part of the
house which it serves. Then when the " lights go out " in
a certain room, it is a simple matter to identify and replace
the burned-out fuse. In some of the older wiring layouts
there may be two fuses to each circuit, and accordingly
two fuses may have be to replaced to reestablish service.
There is now on the market a circuit-breaking device
(circuit-breaker) which eliminates fuses. When a
circuit becomes overloaded this device automatically
opens before any harm is done. After removing the
cause of the overloading, it is necessary only to snap
its handle as you would an ordinary wall switch to have
the circuit-breaker resume service. The circuit-breakers
may also be used to turn off circuits if repairs are to be
made. Where fused panel boxes are used, the fuses
may be removed for the same purpose.

Wiring Methods.

The safety precautions for wiring systems are governed
largely by the National Electrical Code of the National

WIRING FOR THE HOME 57

Board of Fire Underwriters and by the local inspection
departments. The Code does not attempt to state
adequacy from the standpoint of convenience for any
given installation but simply fixes the minimum require-
ments which must be met by the contractor for safety
in order that his work be approved by the inspection
department having jurisdiction.

Of the various methods that may be used in the
wiring of houses, four of the more usual ones are briefly
discussed.

Knob and Tube.

This method employs single rubber-covered wire,
the rubber covering to have a covering of fibrous mate-
rial braided directly on to its surface. This wire is
concealed between partitions and floors and is supported
on porcelain knobs. Porcelain tubes are used where
it is necessary to tunnel through wooden joists, beams,
or studding. The wires are kept separated from each
other by at least 5 inches and are kept at least 1 inch
away from the surface on which they are mounted. At
those places where it is impossible to keep the wires
separated by 5 inches, each wire is encased in an unbro-
ken length of flexible tubing of fibrous material commonly
known as loom.

Non-metallic-sheathed Cable.

In this case the two conductors, each separately
insulated with rubber and other insulating-material
layers, are contained in an outer sheathing of braided
fibrous material. This cable is run from outlet to
outlet in continuous lengths without joints or spliced-
in connections. The cable itself is fastened directly
to the wood joists, studs, etc., by means of metal straps
similar to those used for supporting water pipe to joists
and beams.

58 LIGHT IN THE HOME

Armored Cable.

The armored-cable assembly consists of a wound
flexible-metal cover over rubber-insulated wires. As
in the case of non-metallic-sheath cable the assembly
is run from outlet to outlet in continuous lengths.
The cable is fastened with straps similar to those used
for water pipe, and when it is necessary for it to pass
through wood joists, studs, etc., holes are bored in the
center of the members, and the armored cable is placed
directly through these holes. The armored covering
of the assembly is both mechanically and electrically
connected to all outlet boxes and fittings.

Conduit.

In this case all outlets are supplied by rubber-covered
wires which are brought from the panel box through
metal pipes, termed conduit. In practice the entire
assembly of conduit is put in place, and the wire
drawn into the conduit afterward. From the order
of procedure in the original installation it is obvious
that any or all lengths of wire may be withdrawn from
the conduit at any time and accordingly replaced.

Branch Circuits.

Branch circuits for various lighting and appliance
arrangements and ratings are either defined or described
in the National Electrical Code. An interpretation
of these definitions and descriptions along with further
suggestions pertaining to these circuits follows :

Lighting branch circuits are circuits supplying electrical
energy to lighting outlets only. Number 14 wire may
be used, but the length of run (panel box to outlets
served) should be taken into account to minimize
voltage drop to 2 volts or less. As branch circuits
in general, except as described in following paragraphs,
should be protected by fuses of no greater rated capac-

WIRING FOR THE HOME 59

ity than 15 amperes at 125 volts, lighting branch
circuits should be protected by fuses of no greater
rated capacity than 15 amperes at 125 volts.

Combination lighting and appliance branch circuits
are circuits supplying energy to both lighting outlets
and appliance outlets. Fixed or portable electrical
appliances each rated at 660 watts or 6 amperes or less
may be connected to this type of circuit. This type
of circuit might normally be applied to the ceiling fix-
ture of a living room, and the convenience outlets
in the bedrooms above it. Number 14 wire may be used,
and fuses of no greater rated capacity than 15 amperes to
protect the circuit. Practically all of the smaller appli-
ances such as toasters, waffle irons, table grills, percolators,
etc., may be used on this type of branch circuit.

Ordinary appliance branch circuits are circuits supply-
ing electrical energy to permanently wired or attachment-
plug outlets, i.e., appliances or convenience outlets
or a combination of them. Such circuits are not to
be employed for permanently connected lighting fix-
tures. The receptacles at the outlets and the attach-
ment-cord plugs on the appliances are not to be rated at
over 15 amperes, 125 volts. Number 14 wire may be
used, and the circuit may be fused at 15 amperes. As
in the case of other branch circuits, wire sizes should be
selected to minimize the voltage drop to 2 volts or less.
Fixed or portable devices, each rated at not more than
1,320 watts or 12 amperes may be used on ordinary
appliance branch circuits. All of the smaller appliances
and certain of the heavier current-consuming devices
may be used. Illustrative of the latter are 1,200- watt
tailor irons, 15-pound 1,200-watt laundry irons, single-
unit 1,000- watt hot plates, etc.

Medium-duty appliance branch circuits are similar
to ordinary appliance branch circuits but are wired with
No. 10 wire and fused at 25 amperes. They are limited
to 125-volt circuits. Fixed or portable electrical appli-

60 LIGHT IN THE HOME

ances, each rated at not over 1,650 watts or 15 amperes,
may be supplied by this type of branch circuit. This
type of circuit is more specifically for locations in which
appliances larger than 660 watts or 6 amperes are likely
to be used. The laundry, kitchen, and bathroom
are examples of the locations involved.

Heavy-duty appliance branch circuits are two-wire
branch circuits which are wired with No. 10 wire and
fused at 25 amperes. They are limited to 250-volt
circuits. Fixed or portable electrical appliances, each
rated at not less than 1,650 watts and at not more than
20 amperes, may be supplied by this type of branch cir-
cuit. Attachment plugs and receptacles when used must
be rated at not less than 20 amperes, 250 volts. Certain
of the hot-water heaters, two- and three-unit hot plates,
etc., would be used on this type of circuit.

It will be noted that each of the types of circuits
other than the lighting branch circuits allows the use
of more than one appliance of a given range of rating
to the particular kind of circuit involved up to and includ-
ing devices rated at 20 amperes, 250 volts. When,
however, devices are rated at 20 amperes or more, only
one such device may be supplied with a given branch
circuit. The majority of electric ranges would accord-
ingly require a separate branch circuit.

Branch -circuit Wire Sizes.

! The National Electrical Code does not directly
specify wire sizes for ordinary branch circuits (that
portion of a wiring system extending from the panel
box containing fuses to the lighting and appliance
outlets) except the requirement that nothing less in size
than No. 14 B. & S. gauge shall be used for this service.

The Code in this case as in many of its provisions
provides primarily for safety. Number 14 wire does
carry 15 amperes, the limit as set by the fuses required on
ordinary branch circuits. Actually it will carry this value

WIRING FOR THE HOME 61

of current for an unlimited distance, but it does not carry
this current for any considerable distance before the loss
of voltage becomes of sufficient magnitude to warrant con-
sideration. Voltage drop in circuits cannot be entirely
eliminated, for all known conductors offer some resist-
ance to the flow of current. Voltage drop can, however,
be minimized by using sizes of wire which take into

TABLE VI. — ALLOWABLE CARRYING CAPACITIES OF WIRES*

Wire Size, Amperes,

Gauge No. Rubber Insulation

18 3

16 6

14 15

12 20

10 25

8 35

6 50

4 70

2 90

* From the National Electrical Code.

account the voltage drop likely to be encountered and
also by providing a liberal number of branch circuits.
Good wiring practice allows a 2-volt drop in a given
branch circuit. The limits of the use of No. 14 wire to
hold voltage drop to 2 volts is further visualized by
referring to Table VII.

For short runs, designed for full allowable current (15
amperes), it is satisfactory. Runs over 30 to 40 feet
require wire sizes larger than No. 14 wire, and even
though this size of wire is and has been predominantly
used for branch-circuit wiring of houses, its use will
undoubtedly diminish in the future. All electrical
devices are designed to operate most efficiently when
connected to circuits furnishing the voltage for which
they were designed, and usually this value is indicated
on the device. This is particularly true in the case of

LIGHT IN THE HOME

tungsten-filament incandescent lamps. One hundred
and eleven volts applied to a one hundred and fifteen
volt lamp represents a case where the circuit is only
4 volts low, but it is sufficient to reduce the amount of
light about 12 per cent, while the electrical energy con-

TABLE VII. — BRANCH-CIRCUIT WIRE SIZES REQUIRED TO

RESTRICT VOLTAGE Loss TO 2 VOLTS (Two WIRE, 115-

VOLT CIRCUITS)

Watts per Circuit

Length
of

100

200

300

500

750

1,000

1,500

1,725

2,000

3,000

Circuit,1
Feet

Amperes per Circuit

0.87

1.7

2.6

4.4

6.1

8.7

13.1

152

17.4

26.1

100

150

200

1 The length of wire is twice the length of the circuit. The length of
circuit is the distance between the panel box and the outlet.

2 Fifteen amperes is the allowable current capacity of No. 14 wire as set
forth in the National Electrical Code.

sumed in the lamp is reduced only slightly over 5 per
cent with the amount of light decreasing over twice as
fast as the electrical energy consumed decreases. It is
not difficult to see that proper voltage is an important
consideration.

Wiring Outlets.

Each room in the house, as well as the halls, the base-
ment, the attic, and the garage should be wired to include

WIRING FOR THE HOME

FIG. 15. — Wiring layout suggested for the procurement of electrical comfort
and convenience. Typical first-floor plan.

LIGHT IN THE HOME

FIG. 15-A. — Wiring layout suggested for the procurement of electrical comfort
and convenience. Typical second-floor plan.

WIRING FOR THE HOME

REAR ENTRANCE

LAUNDRY

FRUIT
CELLAR

FIG. 15-B. — Wiring layout suggested for the procurement of electrical comfort
and convenience. Typical basement plan.

66 LIGHT IN THE HOME

all the following outlets : lighting outlets, wall-switch out-
lets, and convenience outlets. By subdividing these into
their respective groups they can be discussed collectively
in detail with regard to the suggestions and recommenda-
tions for the number, position, and general requirements
for their installation. Following is this subdivision:

Lighting Outlets.

Ceiling Outlets.

A very good rule to follow is to have a center ceiling
outlet in every room of the house, although sometimes
the architectural treatment of certain rooms prescribes
that the ceiling fixture be omitted. It is recommended,
even where a ceiling fixture is not installed, that when
building, the rooms be wired for a fixture, particularly
the living room and bedrooms. In such cases the outlet
is capped over and plastered or otherwise covered,
ready for easy connection at any future time.

Ceiling outlets will usually be found preferable to
wall-bracket outlets in the basement of the house,
since these ceiling outlets will be used for utility pur-
poses and should, therefore, be carefully placed in
relation to their uses.

In houses where the third floor is an open square
or rectangular attic, usually one ceiling outlet will
be sufficient, unless the attic is large, and then two
or more are recommended. It is well to keep in mind
that at some future time the third floor may be fin-
ished into separate rooms and the wiring should be
treated in accordance with that consideration.

Garages are most satisfactorily lighted if the ceiling
outlets are placed over the hood and at the rear of the
car and not centered over the top of the car. For two-
car garages, three outlets are recommended, one over
the hood of each car and one between and at the rear
of the cars. An exterior light on the garage is recom-
mended.

WIRING FOR THE HOME 67

Wall-bracket Outlets.

In living rooms, dining rooms, and bedrooms, wall
brackets are primarily intended to provide decoration
and, therefore, may be installed whether or not a center

WIRING SYMBOLS

<j>-CEILING OUTLET
Kj>-WALL BRACKET

-(>>" DROP CORD
N^f- DOUBLE CONVENIENCE OUTLET

-^>--FLOOR OUTLET

@- SPECIAL PURPOSE OUTLET

S1- 1 WAY SWITCH

S°- AUTOMATIC DOOR SWITCH

SP- SWITCH AND PILOT

FIG. 16. — Interpretation of symbols for reading the wiring of house plans.

lighting outlet has been incorporated in the wiring plan.
Unless indirect brackets are contemplated, it is inadvis-
able to depend upon the wall brackets to take the
place of ceiling fixtures. It is recommended that the
wall brackets be placed on opposite walls for balance
in distributing the light evenly, particularly in those

68 LIGHT IN THE HOME

rooms where there is no ceiling fixture. Wall brackets
should scarcely ever be centered in wall spaces, because
their presence on these areas interferes with the hanging
of pictures and tapestries and with the placing of
high pieces of furniture. It is usual to place wall
outlets 5 feet, 6 inches from the floor, except where
ceiling height or the design of the brackets calls for
a higher or lower position.

The wall outlets in the laundry and kitchen are usually
placed over the laundry trays and sink. They will
be more satisfactory in providing light closer to the
work if they are mounted approximately 5 feet from
the floor. The wall outlets in the bathroom should
also be mounted 5 feet from the floor, one on each
side of the mirror.

Outdoor Outlets.

The type of front entrance dictates whether a pair
of brackets, lanterns, or a ceiling lantern is used. For
the large, covered front porch, a ceiling outlet may
be provided; while the shallow porch or the uncovered
platform, so universally popular at present, invites
different treatment — usually a single wall outlet on
each side of the doorway or one centered directly above
it. If only one wall outlet is installed at one side of
the doorway, it should be placed, if possible, on the
door-opening side. Where architectural detail permits,
the lighting result from a pair of brackets possesses
enough points of superiority to warrant their use.

For all rear entrances one lighting outlet will usually
be sufficient. This may be placed directly over the
door, at one side of it, or, where there is a porch, the
outlet may be installed in the ceiling.

Many houses are wired with a lighting outlet at the
rear corner of the house on a level with the second floor.
Such an outlet can provide lighting for the entire length

WIRING FOR THE HOME 69

of the driveway to the garage. It is usual to connect
this and other exterior outlets to a master switch.

Wall Switches.

The principal lighting fixture in each room should
be controlled by a wall switch placed on the door-opening
side of the most used doorway and about 4 feet from
the floor. In rooms where there is more than one
important doorway, a second or a third switch (com-
monty called three-way and four-way switches) is
recommended if the doorways are more than 10 feet
apart. Where there is more than one wall switch
at any one place, these switches are all put under one
cover plate. It is inadvisable, however, to have more
than three switches at one place, simply to avoid con-
fusion in remembering which lights or convenience
outlets each controls.

Exterior house lights near door entrances should be
controlled by wall switches within the hall entrances.

Good wiring practice prescribes that all wall brackets
in a room be placed on a wall switch for convenience.

Three-way switches are commonly used in the down-
stairs and upstairs halls to operate the lighting outlets
in either place . Three-way switches sh ould be installed at
each doorway of bathrooms located between bedrooms
for the convenience of operating the lighting outlet
upon entering either door. It is also advisable to con-
trol garage lights by three-way switches, one placed
in the garage, the other in the house. If an outlet
is controlled from more than two different places, two
of the places of control employ three-way switches,
while all additional points of control use switches known
and specified as four-way switches. These switch
designations are used by contractors, architects, and
builders, primarily to convey the information on neces-
sary wiring and types of switches required.

70 LIGHT IN THE HOME

The master switch is discussed under the subdivision
of Special Considerations.

Convenience Outlets.

Good wiring dictates that convenience outlets (some-
times termed base plugs or floor plugs) be placed on
all wall spaces large enough to accommodate any piece of
furniture, and at least one on each of the four walls of a
room. Extensive experience indicates that these outlets
should be placed so that no point in any unbroken wall
space is more than 6 feet from an outlet. " Standard'7
convenience-outlet bodies and cover plates should be used
so that they will serve both the standard appliance and
lamp plugs.

Whether the convenience outlet is placed in the base-
board or in the wall a few inches above it will usually
be determined by local practice and personal preference.
Of course, in those rooms such as the pantry, laundry,
kitchen, and bathroom, convenience outlets will be
used largely to connect appliances and not lamps and,
therefore, will be found more convenient to reach
easily if they are installed in the wall 3 to 4 feet above
the floor.

When ventilator fans and electric wall clocks are
to be used, a convenience outlet should be placed near
them for convenient connection, thereby eliminating
trailing and unsightly extension cords. Many of these
appliances may not be in general use at the present
time, but the wiring should be contemplated with the
modern devices and future developments in mind,
for the cost of installing additional outlets will be greater
after the house is built than during its construction.

It is recommended that duplex (double) convenience
outlets be installed on all combination lighting and
branch circuits and also on ordinary appliance branch
circuits throughout a house, because they provide,
at very small additional expense, twice the facilities

WIRING FOR THE HOME 71

for connection as do single convenience outlets. Con-
venience outlets in the dining room, kitchen, and
laundry (or those which will be used to serve larger
appliances) are frequently placed on either ordinary or
medium-duty appliance branch circuits.

The convenience and lighting outlets in any one
room should be placed on separate circuits. This
wiring arrangement eliminates total darkness in any one
room if the fuse which controls either the lighting
circuit or the convenience-outlet circuit blows out.

At least one convenience outlet is recommended for
both the garage and the unfinished third floor. Such
outlets will be of value for connection of lights on portable
extension cords in either of these places where they
are so frequently needed.

It is well to install weatherproof convenience outlets
out of doors. One or more placed near the front door
will provide a means of having lighted decorations
at the entrance for Christmas effects or other seasonal
ornamentation. If only a single outlet is installed,
it should be placed on the porch at the hinged side of
the door, thereby allowing the placing of lighted decora-
tions on the door. Another convenience outlet will
be useful if there is a small garden to be lighted. The
outlet should then be placed on the side of the house
nearest to the garden. These exterior outlets should
be mounted approximately \Y% feet from the ground
in the foundation of the house.

Floor Outlets.

It should be kept in mind by those who wish to use
appliances on their dining tables that an outlet in the
center of the dining-room floor will be of great con-
venience. The placing of a floor outlet in the living-room
floor near the center of the room or near the fireplace is
helpful in supplying light for furniture groupings centered
in the room or placed before the fireplace.

72 LIGHT IN THE HOME

Special Considerations.

There are many " refinements " which will add greatly
to the electrical convenience and comfort of the home.
After full consideration and proper allowance for a
good practical wiring installation has been arrived
at, specialties may be considered. When the reverse
procedure is indulged in, with a given expenditure,
the wiring installation too often contains clever special-
ized conveniences but, unfortunately, is lacking in
the essential and practical elements that find everyday
use. For example, automatic door switches for closet
lights are the acme of convenience, but if funds are
limited, the higher price of the switch mechanism and
its installation should be borne in mind.

The master switch is a highly recommended refine-
ment for emergencies. This is a switch which is supreme
in its control of all the outlets connected to it. It is
usual to wire exterior house lighting and some first-
floor lighting to the master switch. The switch is
usually placed in the master bedroom.

There are countless wiring devices which will be of
value if they are installed. Prominent among them
are tell-tale pilot lights which show when a circuit is
turned on. For example, those for the iron or the
cellar light come under this category. Bell ringers
should be connected to the wiring system, thereby
supplying current for door bells and buzzers. Luminous
paint or compound, luminous screws, or luminous pend-
ants may also be used to indicate the location of the
device itself, making it easy to find in the dark.

Future Provisions.

It is well to have extra circuits on the panel board
for future connection, because this provides for expansion
in electrical growth. Appliances not even known to
us at present may be developed in the future. Such

WIRING FOR THE HOME 73

devices would make demands upon the wiring system
for which it was not designed; overloaded circuits
would result. Electrical air conditioners, water heaters,
heavy-duty irons, built-in bathroom heaters, and many
other appliances, quite uncommon today, will undoubt-
edly be in everyday use in most homes within a short
span of years. This should be kept in mind when
wiring a new house or rewiring a house already built.

CHAPTER VII
LIGHTING EQUIPMENT

Lighting Effect.

Once the wires which carry the electric current are
brought into the several rooms of the home to carefully-
determined ceiling, wall, and convenience outlets, the
problem then becomes that of selecting the right equip-
ment to produce ultimately appropriate and satisfactory
lighting. Paradoxically, the fulfillment of these require-
ments, which would seem to be paramount in all light-
ing equipment, has been largely lost sight of in the
slavish imitation of those historic forms which carried
earlier illuminants and in the meticulous seeking
after traditional architectural features. Although it
is often desirable to reproduce these old, artistic forms
and usually essential to create designs appropriate
architecturally, these aims should never precede in
importance that primary purpose of producing useful
and charming lighting effects.

Light Source.

The human race has evolved through so many
centuries with an artificial light which allowed but one
uncontrolled effect — that of the open flickering flame-
that many designers even today are prone to confine
themselves too closely to old habit-accustomed usage
as found in the earlier candelabra, chandeliers, and
lanterns instead of utilizing the infinite possibilities
of the completely controllable modern illuminant —
the electric lamp.

This concentrated light source — the modern electric
lamp — because it is so many times brighter than the

LIGHTING EQUIPMENT 75

original flame, if it is to be kind to the eyes and to the
appearance of its surroundings, must be so shaded as
to control and direct the light comfortably and effec-
tively. The argument is advanced that in adding
shades to the reproductions of the old forms, the spirit
of the original is lost. Actually, is not its soft, pleasing
appearance being preserved while the gross mechani-
cal imitation (the lamp bulb) is being concealed? Cer-
tainly modern lighting equipment should not be a mere
copy of old forms but should provide a more fitting
housing for electric lamps which can then furnish any
desired lighting effect, at the same time incorporating,
when desirable, the characteristic detail of older archi-
tectural forms.

Systems of Lighting.

Multitudinous lighting effects are obtainable from the
varied combinations with varying equipments of two
lighting systems, direct and indirect. A direct system
of lighting is one in which the lower portion of an interior
receives most of its light directly from a visible lighting
fixture. Direct, lighting is commonly depended upon
for lighting specific areas and results in fairly definite
shadows unless it is properly diffused. Light, shade,
and depth that give interest to a room are created by
this type of lighting.

An indirect system of lighting is one in which the lower
portion of an interior receives its light indirectly by
reflection from the ceiling alone or ceiling and upper
walls. The light sources may be concealed in opaque*
or very dense diffusing bowls, suspended from the ceil-
ing or in vases, ornaments, cornices, wall boxes, or
floor and table lamps. This type of lighting, which
depends upon a light-colored ceiling, produces a general,
evenly diffused, nearly shadowless illumination and is,
therefore, most desirable in relieving harshness. Used
alone, however, its effect by its very evenness is flat,

LIGHT IN THE HOME

uninteresting, and tends to be monotonous. Com-
binations of these two effects (termed semi-indir*ect
lighting) in varying proportions of direct and indirect
lighting provide us with a means of obtaining the good
points of both systems.

The resultant efficiency and effectiveness of these
systems in the last analysis depend upon the wattage

FIG. 17. — Fixture sketches which illustrate the three systems of lighting;
A, direct; B, indirect; and C, semi-indirect.

used; the reflecting, diffusing, and transmitting quality
of the surrounding equipment: the position of the
equipment in the room; and the finish of the interior;
so that all these factors need to be taken into account
in the selection of the lighting equipment for a given
room.

Although the illuminating qualities of lighting equip-
ment are especially emphasized, its decorative quali-
ties should be considered simultaneously. It should

LIGHTING EQUIPMENT 77

harmonize with its surroundings in scale, finish, work-
manship, and architectural design and should offer
decorative appeal both lighted and unlighted. This
points to the desirability of incorporating a decorative
element of light, especially when the lighting effect
is being gained from opaque equipment. This element
gives the fixture vitality and interest and is often more
pleasing when it is obtained from a number of light
sources.

Ceiling Fixtures.

The lighting equipment for general use in the home
may be classified into three distinct types familiarly
known as ceiling fixtures, wall brackets, and portable
(floor and table) lamps. The term " fixture'7 is unfor-
tunate, for it carries the very definite implication of
permanency, and, after all, there is no reason why
fixtures should not be changed with advances of knowl-
edge and an improvement of light sources. The term
probably came into common usage with the advent
of gas lighting when, on account of the gas pipe to which
it was attached, the equipment was indeed " fixed. "
Then, when electricity first became practicable but
not too dependable for home use, jutting appendages
were added to the gas fixture to accommodate the wires,
sockets, and lamp bulbs, and there resulted that unsightly
gas and electric fixture which unfortunately is not yet
an historical relic.

Obsolescence.

In a national survey of residence lighting conditions
made in 1923, it was definitely established that over
30 per cent of the ceiling fixtures of the twelve million
homes which were then wired for electricity were obsolete
types producing unsatisfactory lighting. The accom-
panying chart (Fig. 18) pictures these types and also
shows the prevalence of these fixtures in the separate

LIGHT IN THE HOME

rooms of the home. Furthermore, estimates based
on observations indicate that 50 per cent of the remaining
fixtures could not be approved because they comprised
either bare lamps or lamps shaded so inadequately
as to be equally unsatisfactory.

IVU

.•i

A f\

! •

Z
bl

f\ f\

C f\

A. f\

5
0

2
O

** \J

*^n

o
tr

z
o

Q f\

o
w

tL\J

10
n

—

_ § _

FIG. 18. — Percentages of total ceiling fixtures in various rooms and in entire
home which are unquestionably obsolete.* Results apply only to rooms
indicated and not to basement and closets where, for example, drop cords
may be satisfactory.

History of Fixture Change.

The complete lack of any artistic merit in the earliest
fixtures designed for the use of electricity soon led to
the discontinuance of their manufacture, and then
came the great popularity and vogue for fixtures which,
although more artistic, were designed, unfortunately'
for use with unshaded, round-bulb lamps. Although
these fixtures when unlighted are esthetically an advance,

* Analysis of Home Lighting Contest Primer. AT. E. L A Publication
25-19, 192^1925.

LIGHTING EQUIPMENT

iH*Ptr

FIG. 19. — Typical modern ceiling fixtures of approved design.

Direct lighting Direct lighting

Multiple Direct Single

semi-indirect semi-indirect

Semi-indirect Totally indirect

80 LIGHT IN THE HOME

they introduce when lighted a jarring, uncomfortable,
inartistic element, because they offer no softening
control or distribution of the light.

The trend now is very definitely away from the use
of the round-bulb lamp or any equipment utilizing
visible light sources and toward ceiling fixtures which
entirely conceal the lamp bulbs and so diffuse, reflect,
and control the light that desirable lighting effects
are produced. Although lighting fixtures take on a
limitless variety of shapes, styles, and finishes, actually
the majority of satisfactory fixtures fall into one of
three principal types: the enclosing unit, the shaded-
candle fixture, and the inverted fixture. The enclosing
unit, usually made of diffusing glassware or parchment,
provides direct light and may be hung within a few
inches of the ceiling, flush with it, or recessed in it.
The shaded-candle type of fixture (preferably with
special built-in direct and indirect components for dining-
room use) produces a partial semi-indirect lighting
effect, usually with a predominance of direct light,
and is suspended several feet from the ceiling. The
inverted fixtures, either with single bowl or with a
number of smaller bowls, result in semi-indirect lighting
predominating in indirect light. These are generally
hung one to three feet below the ceiling. A very few
totally indirect fixtures for the home are manufactured
for use mainly in children's rooms, for there it is desir-
able to avoid any possibility of the harsher direct light
striking immature eyes. It is to be borne in mind that
the successful use of the indirect or semi-indirect system
of lighting is dependent always upon a very light-colored
ceiling finish. Light-colored walls are also desirable,
although they need not be so light as the ceiling.

The size and finish of the room, the height of its
ceiling, and the lighting effect best suited to its require-
ments are the determining factors in choosing the
room's fixture.

LIGHTING EQUIPMENT 81

Wall Brackets.

Wall brackets, which fulfill very definite needs for
utility and decoration, are of three types, the pendent,
the inverted, and the candle. The pendent bracket
with the lamp so shaded with white diffusing glassware
as to direct the light downward is usually a utility one,
designed to provide local light, as, for example, at the
sink or over the range. The upright wall bracket
may be either utilitarian or decorative, depending upon
its design and shading medium and placement. Upright
brackets equipped with white diffusing glassware and
40 or 60-watt inside-frosted lamps and hung at face
height on either side of a mirror are indeed 100 per cent
utility lights. On the other hand, this same type of
bracket in a more artistic form equipped with denser
glassware, mica, parchment or silk, and a low-wattage
lamp (15 to 25) may prove a very delightful decorative
spot for the halls, dining room or living room. This
same decorative type of bracket designed for higher-
wattage lamps serves both utility and decorative needs.
The candle-type bracket should usually be depended
upon for its decorative qualities only and must, of course,
be well shaded.

Shades.

Shades of silk, parchment, glass, etc., may be used
and, if thoughtfully selected, effectively change harsh
raw light into comfortable illumination and afford,
as well, pleasing decorative elements. In choosing
shades for fixtures or portable lamps, and especially for
the latter, consideration must be given to their shape
and color. The shade should be deep enough so that
the lamp bulb is not visible and should be shaped to
throw the light where it is needed. Open-top shades are
doubly useful, for they permit light to strike the ceiling
from which it is diffused generally in addition to the

LIGHT IN THE HOME

FIG. 20. — -Recommended wall brackets which illustrate the newer trend of
lighting practice.

LIGHTING EQUIPMENT 83

direct local light. The material of the shade should be
translucent enough to allow ample light to come through,
with no bulb outline showing. In lamp shades, red,
blue, and green are wasteful colors in that they absorb
a high percentage of the light. In addition, the strength
of these colors often distorts the color scheme of a room
so that its beautiful daylight appearance is destroyed at
night. Pale colors, on the other hand, enhance the
decoration of a room. In general, those glowing colors,
tints, shades, and light-colored mixtures of red, orange,
and yellow that give the effect of sunshine are a safe
choice. Eliminating pure white, they give the greatest
amount of light and also a quality of light which is the
most pleasing. At the same time, the result will usually
harmonize with almost any color scheme. The pre-
dominating colors of the room may be picked up as
decorative motifs on the shade or in its binding. The
linings should always be light colored so that the light
from the lamp will be well reflected.

Portable Lamps.

Portable lamps, because of their easy portability and
decorative value, solve many lighting problems for the
home, particularly that of the renter, and prove a most
essential supplement to the ceiling and wall fixtures.
They should, with few exceptions, be selected for their
utilitarian as well as their artistic qualities, for indeed
both floor and table lamps can be beautiful and at the
same time perform definite lighting functions. The
height of a portable lamp is of considerable importance
and depends largely upon the location in which it is to
be used. For example, a tall lamp on a low table beside
a low lounging chair is unsuitable, for then the lamps
(bulbs) are uncomfortably visible to anyone occupying
the chair. On the other hand, a low base with a
spreading shade to throw the light beyond the table
and at the same time avoid any possibility of its reach-

LIGHT IN THE HOME

LIGHTING EQUIPMENT 85

ing the eyes is a wise choice for this particular furniture
group.

A number of the disadvantages of the ordinary floor
and table lamps have been overcome in the indirect
lamp. This lamp is equipped with a single socket
(intended for a large-wattage lamp, 200 or 300 watts)
and a reflector which directs the light to the ceiling for
redistribution (Fig. 22, B). The latest trend in the
indirect lamp is toward a more flexible model which
incorporates three or four sockets for smaller-wattage
lamps, 60 or 100 watts, so that one or more may be used
at a time and thereby attain the amount of light needed
for the purpose of the moment (Fig. 22, A). When the
maximum light is needed, it is easily available but does
not need to be turned on when lesser amounts will
suffice.

One recent development offers a really ideal reading
lamp (Fig. 22, C) which is obtainable in either the floor
or the table type. Its main purpose is to produce soft,
plentiful illumination and to avoid that harsh direct light
from the lamp bulbs themselves which so often rebounds
from the work into the eyes and is so annoying. To this
end, the lamps, instead of projecting from the usual
sockets attached to a center rod beneath the shade, are,
in this newer lamp, embedded in a shallow metal dish
which is wide enough to cut off any direct downward
light from the lamp bulbs. Most of the light strikes
the lining of the shade, which must be white or very
light in color so that it will act as an effective surface to
reflect the light down where it is needed. Although
some of the light rays are allowed to escape out of the
top of the shade for a part of the general lighting of the
room in which the lamp is used, many are reflected down-
ward by a small aluminum cone placed just above the
lamp bulbs. This portable lamp is designed for three
60-watt lamps (bulbs) and includes a switch which
controls each lamp separately so that for flexibility, one,

LIGHT IN THE HOME

FIG. 22. — Illustrating the arrangement of lamp bulbs and reflectors incor-
porated in the portable lamps designated in Fig. 21 as A, B, C, and D,
respectively.

LIGHTING EQUIPMENT 87

two, or all three may be turned on or off as desired — one
lamp (bulb) merely to keep the shade luminous; two lamps
to provide some general illumination; and all three
lamps for reading, sewing, or other close visual work.
The resultant light on the book or sewing is unusually
and amazingly plentiful, free from any annoying reflec-
tions, and most restful to the eyes.

With the increasing popularity of floor and table
lamps and the consequent larger market for them,
there are being developed a great number of very well-
designed models which, beneath the shade, conceal
equipment producing most satisfactory direct as well as
indirect components of light (Fig. 22). These, it is
hoped, will so attractively point out the benefits of
good lighting that they will lead to the greater
appreciation and utilization of all well-designed lighting
equipment.

Maintenance.

If the initial efficiency of the lighting equipment is to
be maintained and it is economically advisable, a regular
schedule for cleaning must be established. Investiga-
tion reveals the astounding fact that even in the most
orderly households the lamp bulbs and the shading
equipment are seldom, if ever, touched by duster or
water. It is also a fact that when dust is allowed to
accumulate on the lamps and shades over a period of two
or three months, the decrease in light output is of the
magnitude of 15 to 35 per cent, the variation depending
upon the location and the types of units used. In the
kitchen, for example, where there are constant greasy
fumes, the lighting units should be washed with soap and
water frequently in order to maintain the high level of
illumination this room requires.

Also lamps that are burned in inverted equipment will
need especial and frequent attention, because this type
of unit is an excellent and speedy dust collector.

88 LIGHT IN THE HOME

Ultra-modern Trends.

Lighting equipment shows an increasing tendency
toward the incorporation of some of the characteristict
of Vart moderne, which abounds in flat surfaces, straighs
lines, angles, and general simplicity. Also with the
growing appreciation of lighting there is the tendency
toward building in luminous panels, coves, and other
constructions whereby the light source becomes an
integral architectural feature of a room. Due to the
rather specialized character of this type of installation,
space does not permit of more than its mention.

Specifications for Evaluating Lighting Equipment.

To encourage the availability and acceptance of better
home-lighting fixtures, the Illuminating Engineering
Society and the Association of Edison Illuminating
Companies have evolved specifications1 by which a
fixture may be scientifically and accurately evaluated.
All those factors which contribute to the satisfactoriness
of a fixture are separately considered and rated under
the three classifications — illumination qualities, con-
struction, and appearance. The method of evaluating is
so worked out as to pass and thereby recommend
only fixtures which meet the specified illumination
qualifications.

By way of illustration of this appraisal system
and its specific application, two of the fixtures shown
in Fig. 19 (A, the direct lighting fixture in the upper
right-hand corner of the illustration; and B, the direct
lighting fixture in the center) are rated as shown on
page 89.

Some notion of the method of determining the ratings
which a fixture merits may be gained from the following
very brief discussion of each qualification.

1 Transactions of the Illuminating Engineering Society, vol. XXII, p.
1027, New York, 1927.

LIGHTING EQUIPMENT 89

TABLE VIII. — FIXTURE SPECIFICATIONS AND RATING METHOD

Maximum
Possible
Rating

Rating
Attained,
Fixture A

Rating
Attained,
Fixture B

I. Illumination qualities:

1. Efficiency of lamps employed

2. Light output of fixture

3. Maintenance of light output

4. Suitability of distribution. . . .

5. Freedom from shadows

6. Variable distributions

7. Freedom from glare

Total points (must rate at least 20

on point 7 or fixture is rejected)

100

II. Construction, finish:

1. Mechanical construction

2. Electrical construction

3. Ease of assembly

4. Suitability for standard types

of lamps

5. Finish

Total points (passing mark, 80) . . .

100

III. Appearance:

1. Lighted

Individual taste dic-

2. Unlighted

tates rat

Final rating

100

Efficiency of Lamp Employed.

Higher-wattage lamps are more efficient in light output
in terms of energy consumed, and hence fixtures utilizing
the higher-wattage lamps receive the better ratings.
Specifically, a fixture which utilizes lamps of 75 watts
or greater receives the maximum rating of five points;
one utilizing 40 or 60-watt lamps receives but three of the
allotted five points; and one utilizing lamps under 40
watts receives but one point.

90 LIGHT IN THE HOME

Light Output.

By a laboratory photometric test, the total lumen
light output of the fixture is determined. The light
output of the fixture is then divided by the sum of the
lumen outputs of the lamps used therein. The result is
expressed as a percentage and is rated according to the
following scale of values:

TABLE IX. — SCALE OF VALUES FOR RATING LIGHT OUTPUT
Light-output

Percentage Rating

100 20

80 16

60 12

40 8

20 4

Maintenance of Light Output.

This item takes into account the permanence of the
surfaces affecting light output, their freedom from exces-
sive dirt accumulation, and simplicity of cleaning. The
judgment of the appraiser will govern the number of
points allotted.

Suitability of Distribution.

Here again the appraiser will assign points for this
quality in accordance with his judgment as to the merit
of the suitability of the fixture's distribution for the pur-
pose for which it is utilized.

Freedom from Shadows.

Any fixture which does not cause objectionable streaks
and shadows on walls, ceiling, or floor should be credited
with all of the points allotted. Only those which are
definitely undesirable in this respect will be penalized
therefor.

LIGHTING EQUIPMENT 91

Variable Distributions.

A fixture which gives two or more desirable light dis-
tributions of a different character will be credited with
the maximum points not obtainable where only one light
distribution is supplied.

Freedom from Glare.

The points to be accorded to a fixture under this
heading are determined by a comparison test of the
lighted fixture with a device known as a glare standard.
This consists of five 6-inch crystal globes frosted on the
inside and equipped with incandescent lamps, 10, 15, 25,
40 and 50 watts respectively, which represent a very
definite scale of comfort or discomfort, and against which
the fixture is separately compared and rated as follows:

TABLE X. — COMPARISON TEST VALUES FOR RATING FREEDOM

FROM GLARE

Fixture Points

Matching Allotted

10- watt globe 40

15- watt globe 40

25-watt globe 38

40-watt globe 30

50-watt globe 20

Fixtures more uncomfortable to view than the globe con-
taining the 50-watt lamp are rejected.

Mechanical and Electrical Construction.

Fixtures should attain reasonable excellence in mechan-
ical and electrical construction to assure safety and
continuity of service without incurring needless increase
in cost. Reference to the National Electrical Code may
be made for guidance in judging electrical safety, mate-
rial, workmanship, wiring, and operating temperature.

92 LIGHT IN THE HOME

Ease of Assembly.

Fixtures should be simple to assemble and install and
should be accompanied by directions for assembly.
Parts should be easily removable for cleaning and for
relamping.

Suitability for Standard Types of Lamp.

Lamp sockets should be standard, and equipment must
be adapted for standard types of lamps of suitable sizes.

Finish.

Corrodible materials should be covered, and the finish
of all parts should not peel or be subject to damage or
easy soiling during installation or after being placed in
service.

Appearance.

Obviously no definite specifications can here be laid
down. Taste and artistic appreciation must govern.
It should be possible to avoid designs which do violence
to the canons of both and to avoid undue regard for the
dictates of style. No alleged requirement of design
should be permitted to nullify requirements for good
illuminating qualities and good construction.

Cost of Lighting Equipment.

Some indication perhaps should be made of an esti-
mated figure for the cost of lighting equipment for a home.
Exclusive of the portable lamps which are considered in
the furnishing budget of the home, an allowance from
2 to 3 per cent of the cost of the house can produce a very
creditable result. This figure, of course, varies, for it is
affected by a number of considerations, but certainly
the 1 per cent that is too often allowed is entirely inade-
quate and shows a very incorrect evaluation of the impor-
tant role that lighting may play in home making.

CHAPTER VIII
LIGHTING THE ROOMS OF THE HOME

In an age when the lighting art in the commercial and
industrial world has made such encouraging progress, it is
astonishing that the kind of lighting found in the average
home is so far behind good modern practice. Undoubt-
edly, this is due in large measure to the fact that lighting
for the home is not amenable to the degree of standard-
ization which has been practicable for these other fields
and which has made better lighting there more easily
attainable. In the home, on the contrary, there is such a
diversity in size, cost, architecture, decorative scheme,
manner of living, individual family taste, and require-
ments that it has been impracticable to set up fixed
rules for lighting the various rooms.

On the other hand, a close study of the actual lighting
requirements, room by room, points out the possibility
of defined recommendations in so far as lighting princi-
ples and lighting effects are involved. Given the living
requirements of a room, a very definite type of lighting
which will satisfactorily meet these needs may be readily
determined and considered as standard for all similar
conditions. The actual physical form of the lighting
equipment itself can vary in material, workmanship,
scale, artistic detail, and still be in decorative harmony
with the individual room surroundings.

Before the various rooms of the home are separately
considered for their living and lighting requirements —
and it is to be remembered that lighting may and should
contribute abundantly to better living conditions — a few
general lighting principles can well be restated.

94 LIGHT IN THE HOME

If the goal of good lighting in the home — convenience,
eye and nerve comfort, and charm— is to be attained,
care must be maintained to utilize adequate amounts of
distributed light, free from excessive contrasts, and to
shade properly all light sources (lamp bulbs). The
material of the shade, be it parchment, mica, glass, or
silk, aside from being a good and suitable light diffuser
and director, is restricted only by the decorative require-
ments of the room. One fundamental purpose of shading
is to increase the size of the light source and simulta-
neously to decrease the harshness of the light. Shades
which are open at the top and which thereby throw the
light to the light-colored ceiling and walls carry this
principle still further in utilizing these surfaces as larges
and softer light sources. To accomplish these results
effectively, lamps of sufficiently high wattage must be
employed. The actual wattage required for a given room
will depend upon the size of the room, the wood and wall
finish, and the type of equipment used. The age in
which electrical current was expensive is fortunately
over, but too often that spirit of economy necessary
then is now handicapping the freer and more adequate
use of light which is actually one of the cheapest com-
modities today. In this matter of lighting, we have to
overcome the habits of many years' use of uncomfortable,
unattractive, and, in most cases, harmful bare lamps.

Following is a discussion of the specific rooms of the
house and their particular requirements, regardless of
cost or style.

Entrances.

The evening appearance of any home is much enhanced
by warm, cheering light shining forth hospitably from the
front entrance. The lanterns producing this welcoming
glow must fulfill very definite tasks, namely harmonize
with and emphasize the architectural detail of the door-
way, light clearly the faces of guests, and safely illuminate

LIGHTING THE ROOMS OF THE HOME

FIG. 23.— The pair of lanterns fulfills the lighting needs of this doorway,
and the lighted house number because of its size and position is easily visible
from the street 150 feet away.

96 LIGHT IN THE HOME

the steps. Two lanterns, utilizing 40 watts each, open
at the bottom and balanced on either side of the entrance,
fulfill the latter requirements best. Sometimes, how-
ever, a single lantern utilizing at least 60 watts, either
over the doorway or at one side, proves architecturally
desirable. Lanterns equipped with crystal or amber-
diffusing glassware prove most effective.

An illuminated house number, operated by a low-wat-
tage lamp (10 to 25 watts), is a thoughtful courtesy and
proves a great convenience. The number can, also, be
incorporated in one of the lanterns or so placed as to be
illuminated by it. Houses located at more than average
distance from the sidewalk or roadway often require the
placing of illuminated numbers on the lawn to assure
legibility. This type of installation is fed by lead-
sheathed wires buried beneath the lawn.

The side, rear, and garage entrances need utilitarian
lighting, too, although their decorative appearance is not
always so important as at the front entrance.

Hallways.

An impression of the character of a home is gained from
the main hallway, so that special thought should be given
to assure its lighting charm. A lantern type (with dif-
fusing glass panels) or shaded-candle type fixture (with
a total wattage of 40 to 100) usually proves pleasing.
It should, of course, direct considerable light to the
ceiling so that the area will be softly but generally well
lighted and should, too, be so designed as to throw light
on the stairway so that there will be no possibility of
accident. Special precaution should be taken against
the possibility of seeing any part of the bright lamp bulb
upon ascending or descending the stairway, for a harsh,
bright, unshaded light is annoying. If the hallway is
large enough, floor torcheres, a table lamp, or even wall
brackets add delightfully decorative notes. The tele-
phone table should have a small lamp on the stand or a

LIGHTING THE ROOMS OF THE HOME 97

FIG. 24. — This hall fixture with its soft diffusing glassware casts ample
light down the stairway. The telephone table is lighted by the midget lamp
which also makes a most efficient and inexpensive night light.

98 LIGHT IN THE HOME

wall lamp or bracket (using a 25 or 40-watt lamp bulb)
directly over the table to enable one to read the directory
conveniently and in turn locate numbers and letters on
the telephone dial.

For an upper hall and stairway, the lighting unit
should provide good general illumination and plenty of
downward light on the stairway. The back and minor
hallways are satisfactorily lighted with small glass-
enclosing units mounted close to the ceiling equipped
with 25 to 60-watt lamps.

Living Room.

The living room is the setting for such a diversity of
family activities that its lighting must be most flexible
to be truly adaptable. This room is often planned only
for daytime appearance and use, but it must not be
forgotten that in reality considerably more than half of
the family life is spent there, and accordingly its night-
lighted appearance and use should be given equal
consideration.

For those times when plenty of general lighting is
needed, when, for example, there are several tables set
up for games, or the children are playing on the floor,
or the rug is rolled back for the young folk's impromptu
dance, just the right center fixture cannot be surpassed
in effectiveness. In selecting this, the first consideration
is the height of the ceiling. The low-ceilinged room,
which is more prevalent in modern building, main-
tains its size and attractiveness best when the fixture
selected is to hang close to the ceiling and to encase
the lamp bulbs. The higher-ceilinged room allows
somewhat more leeway in selection, for it permits
a fixture to suspend from a few inches to as much as a
few feet from it; the shaded-candle fixture or any of
the more modern semi-indirect fixtures are then usable.
In any case, the ceiling fixture should usually include
a total of 200 watts, even though it is expected

LIGHTING THE ROOMS OF THE HOME

ass

100

LIGHT IN THE HOME

LIGHTING THE ROOMS OF THE HOME 101

to be used always in conjunction with floor and table
lamps.

When a smaller amount of general lighting is desir-
able, as when a few people are gathered for conversation,
the table and floor lamps alone may suffice. When
these are selected with open tops, enough light is allowed
to escape to the ceiling and walls to produce some general
lighting. At the same time, a more balanced lighting
effect in the lower and upper portions of the room
is obtained. As a consequence, those harsh contrasts
so trying to the eyes and so commonly experienced with
all closed-top portables are avoided. Balance in light-
ing is quite as important as balance in furniture arrange-
ment to which today more and more home keepers
are giving attention. Similarly, floor and table lamps
should be placed in the room to maintain balance with one
another and placed to service each furniture grouping.

The recommendation for wattage of lamps used,
of course, varies with the use of the portable lamp,
the character of the shade, and the number of sockets.
Generally, however, it is safe to suggest a 60-watt lamp
(bulb) for a single-socket lamp, two 60-watt lamps
(bulbs) for a two-socket lamp, and two 60 and a 25-watt
lamp when there are three sockets. This latter recom-
mendation allows flexibility in the use of the lamps,
for the small-wattage lamp alone is sufficient to make
the shade luminous and thereby provides a decorative
touch when it is not needed for useful lighting.

The truly hospitable reading chair has, besides a
small table to hold a book and an ash tray, its own
lamp as the final note of comfort. The right lamp
will be selected with regard to the correct height and
the spread of the shade so that the light will fall on
the book and never toward the eyes. A really ideal
reading lamp together with a number of indirect port-
ables which are suitable for reading purposes are dis-
cussed in Chapter VII under Portable Lamps.

102

LIGHT IN THE HOME

FIG. 27. — The floor and table lamps shown are a happy selection for this
oak-paneled room, for their open tops allow plenty of light to escape to the
ceiling for redistribution and their dark color tone avoids any possibility of
trying contrast between the shades and the paneled background.

LIGHTING THE ROOMS OF THE HOME 103

FIG. 28. — The truly hospitable reading chair has, besides a small table for
needed accessories, its own lamp.

104

LIGHT IN THE HOME

FIG. 29. — The vast difference between discomfiture and restfulness, ugliness
and decorative harmony, is clearly indicated in this corner shown with its
unwisely (above) and wisely selected lamp shade (illustrated in Fig. 29 A).
The poorly chosen shade (above) is too shallow, dense in color, and closed
at the top, thus causing harsh contrasts and concealing the oil painting above.

LIGHTING THE ROOMS OF THE HOME 105

FIG. 29 A.

106 LIGHT IN THE HOME

The desk, wherever possible, should be placed to
receive daylight from a window at the left, and. its
lamp should be placed at the left-hand side to avoid
shadows on the page which would otherwise be cast
by the right hand. For the secretary desk, so that
the desk may be closed, a bridge lamp [with a 60-watt
lamp (bulb)] is most convenient.

The davenport is best lighted when a lamp is provided
at each end, although a tall lamp placed in the center
of a table behind it may serve the entire davenport
well. When floor lamps are used, the lamps should
be placed slightly behind the furniture to avoid the
possibility of glare striking the eye.

A piano light is now available which incorporates
two 25-watt tubular lamps and which fits inconspicuously
on the music rack. This lamp performs its duty excel-
lently by sending light upon the music sheet. A floor
lamp placed near may serve. However, the selection
of an entirely satisfactory lamp of the more usual type
for this purpose entails considerable care, for a lamp
providing sufficient spread of light to illuminate the
music sheet exposes bare lamps to the one seated at
the piano, while the one which shields the eyes does
not often provide a sufficient spread of light. One of
the so-called indirect lamps using a 200-watt lamp in
a reflector fills the piano corner of the room with even,
shadowless light. This latter type of lamp may be used
to advantage in those living rooms for which no ceiling
fixture has been provided.

In discussing the lighting possibilities of the living
room, the charm of purely decorative lighting must not
be slighted. Although wall brackets serve utilitarian
purposes on some locations, their chief right to exist
in the majority of living rooms is as vital spots of orna-
ment, and 15 or 25-watt lamps are usually the correct
size. On account of closeness to our usual line of vision
they are sources of real visual discomfort if they are

LIGHTING THE ROOMS OF THE HOME 107

FIG. 30. — The bridge lamp correctly placed at the left of the secretary may
also serve an adjacent lounging chair.

108

LIGHT IN THE HOME

LIGHTING THE ROOMS OF THE HOME

109

FIG. 32. — This new music-rack lamp fits most inconspicuously and performs
its duty excellently.

110

LIGHT IN THE HOME

FIG. 33. — An indirect floor lamp fills the piano corner with even, shadowless
light of which the sheet music receives its adequate share.

LIGHTING THE ROOMS OF THE HOME 111

not shaded. They are usually most attractive when
located in balanced arrangements on opposite walls
and should be placed near enough to the casements
so that they do not infringe upon wall areas that might
be used for hangings, pictures, or furniture placement.

Light ornaments, using varicolored low-wattage lamps,
also introduce interesting and enlivening spots of
decoration.

Dining Room.

There has always been considerable controversy
as to the most satisfactory method of lighting the dining
room, and it seems that here personal taste concerning
the most desirable atmosphere for dining is the con-
cluding factor. There are several types of equipment
available that give good results, and these will be pre-
sented separately. In each case, the motive is to have
the light predominantly on the table, which is after
all the center of interest in this room.

The five or six-light candle fixture is one of the most
popular fixtures for dining-room use and is very com-
mendable when the lamps (40 watts each) are shaded and
when the fixture is hung about 36 inches above the table top.

The semi-indirect type of fixture has its place too
in the dining room, although it does not primarily light
the table. This kind of fixture gives even, general
illumination throughout the room but has a tendency
to be monotonous, although it has a very definite place
in the home in which the children or other members
of the family use this room for study purposes. If
the fixture has but one socket, a 150-watt lamp is usually
necessary; and in the case of multiple sockets, 40 to
60-watt lamps should be used.

Modern adaptations of the old-style dome type of
fixture are smaller (providing 100 watts) and less heavy
and have real suitability when hung low over the table
top — that is, within 24 inches.

112

LIGHT IN THE HOME

FIG. 34. — This modern adaptation of an old-style dome fixture produces
unusual softness and cheer with its rich amber glassware.

LIGHTING THE ROOMS OF THE HOME

113

114 LIGHT IN THE HOME

Special units, usually combinations of these three
types just mentioned, often combine the advantages
of each and eliminate their disadvantages. For example,
a fixture may be designed to incorporate a central direct-
lighting component artistically embodied in the fixture,
furnishing light for the table; an indirect component,
furnishing general lighting for the room; and in addition
a number of light-source areas affording the decorative
touch which is so desirable.

For those people who prefer to eat by the charming
flickering light of wax candles, either the use of a number
of wall brackets or a cove system of indirect lighting
is most heartily recommended to overcome the most
uncomfortable and eye-fatiguing contrasts formed
between the candle flames and the dark surroundings.
In large rooms plaster or metal coves may be mounted
around the room about 18 or 24 inches from the ceiling.
If the room has not sufficient height to allow 18 inches
between the trough and ceiling, this type of lighting
should be abandoned. The inside of the lip of the
trough may be painted black to avoid any spottiness
immediately above the cove on the wall. Either 10-
watt round or 25-watt tubular lamps, having inter-
mediate sockets (10-watt lamps separated by 3^
inches, 25-watt lamps separated by approximately
6 inches), are placed in the trough. In smaller rooms
where the door and window openings are balanced,
troughs of this type may be almost invisibly mounted
over the door and window casements, with the resultant
effect a charming background for the candle-lit table.

Similar cove-lighting effects are also suitable for use
in a number of living rooms.

The breakfast nook should be considered, of course,
as a miniature dining room, but because this room is
primarily used in the early morning, when so often it is
dark and cheerless, a small dome-type unit (60-watt
lamp) of sunny hue seems to give the most cheerful effect.

LIGHTING THE ROOMS OF THE HOME

115

FIG. 36. — This close-to-the-ceiling dining-room fixture has two circuits,
one to spotlight the table top and one to lighten the ceiling for general
distribution.

116

LIGHT IN THE HOME

LIGHTING THE ROOMS OF THE HOME 117

Kitchen.

Plenty of well-diffused illumination is the keynote
of lighting the kitchen. A single diffusing glass-enclosed
unit with a 100-watt lamp at the center of the ceiling
answers the need. Light-colored walls and ceiling
assist in directing much of the light downward and
minimize shadows. However, shadows are almost inev-
itable at the sink, which should always have its own
bracket or pendent light fitted with a white glass shade
and hung 5 feet from the floor or a small enclosing
unit at the ceiling using a 60-watt lamp. Similarly,
a pendent unit over the range or a lamp inside the hood
above may also be required. If the ironing is done in the
kitchen, the daylight quality obtained from the " day-
light" lamp is advisable. In this case the ceiling
unit should be equipped with a 150-watt " daylight"
lamp, and to keep the room uniform in appearance
the local sink and range units should utilize 60-watt
" daylight" lamps.

Bedroom.

It is unfortunate that the central fixture is being
omitted from so many bedrooms in new homes, for
there are times, particularly if the bedroom is also
the dressing room, when that high level of illumination
obtainable best from a center fixture is needed. It
should be of low brightness so that it will not be a source
of discomfort for one lying in bed. Either a glass unit
of good diffusion hung close to the ceiling or an indirect
fixture (100-150 watts) is a happy choice. If the room
is large and formal, and ceiling height permits, a shaded-
candle type fixture is fitting (25 to 40 watts each).
In this latter case, there is usually a separate small
dressing room, and this should most certainly be equipped
with a fixture (60-100 watts) that will insure ample light.

There is a real advantage in placing the dressing
table in front of windows so that when sitting at the

118

LIGHT IN THE HOME

LIGHTING THE ROOMS OF THE HOME

119

FIG. 39. — A dressing table placed and equipped with real^thought for both
day and night make-up.

120 LIGHT IN THE HOME

table, revealing daylight shines on the face, which is
then reflected distinctly in the mirror. Too often the
true aim of lighting at the mirror is misunderstood,
and it actually should be to light the face and not
the mirror. Similarly the artificial light should be
placed to light the face, and accordingly two dressing-
table lamps, equipped with 40-watt bulbs, should be
tall enough to be at face height in relation to the mirror.
Accordingly boudoir lamps on a dressing table, before
which one always sits, should be shorter than on a bureau,
before which one usually stands. Brackets may also
be very satisfactorily attached directly to the mirror
at face height.

The bedtime reading lamp is indispensable, either
on the wall (with a 60-watt lamp) above the bed or on
the night table (with a 60-watt lamp). In the latter
case, the lamp must be high enough to shed light on the
book, and the shade with a wide spread of light should
by all means be open at the top to allow some light to
diffuse into the room to decrease the visually trying
contrast between the lighted book and the otherwise
dark surroundings.

A small lamp (15 watts) fastened under the bed and
controlled by a conveniently placed switch at the head
of the bed proves a great convenience, especially if there
are children or sick persons to be attended during the
night. This simple attachment provides enough light
on the floor to find one's way around without arousing
or disturbing other occupants of the room.

The children's room should be painstakingly lighted,
because their immature eyes are most susceptible to
eye strain. There must never be any possibility of
subjecting these young eyes to uncomfortable bright-
ness, a warning which includes that against allowing
the crib or bed to face the window spaces unless these
are carefully shaded. The lighting unit should be
preferably of the indirect or very dense semi-indirect

LIGHTING THE ROOMS OF THE HOME

121

122

LIGHT IN THE HOME

FIG. 41. — A pull chain right inside the closet door controlling a 60 or 100-
watt lamp makes clothes selection a simple and quick task.

LIGHTING THE ROOMS OF THE HOME 123

type (with 100 to 150-watt lamp). As soon as the
child is old enough to turn a bedside lamp on or off,
one should be provided, for psychologically it is a com-
forting protection against any possible uneasiness in
the dark.

Closets.

Clothes closets can be well lighted by a bracket
light inside and above the door (on the opening side)
controlled by a pull-chain switch or by an automatic
door-operated switch. Although a small lamp might
be fairly satisfactory, a lamp of 60 or 100 watts may
be used to provide really excellent lighting at trifling
expense, because of the fact that it is used but a few
hours a year.

Bath.

In most modern bathrooms proper light at the mirror
will serve to illuminate the entire room. This may
best be accomplished by two upright brackets, one on
each side of the mirrftr, with the light centers 5 feet
6 inches from the floor, which is average face height.
Lamps of 40 or 60 watts will be sufficient, and of course
these are shaded with diffusing glassware. An excep-
tionally large or dark-colored tiled bathroom should
have an additional light at the ceiling, similar to,
although probably somewhat smaller than, the kitchen
unit. Oftentimes the shower stall needs its own light,
and this should be recessed in the ceiling and controlled
by a switch outside the stall.

Sewing Room.

The sewing room, for best eye comfort, should < be
provided with both a ceiling fixture (having, a total
of from 150 to 200 watts) of such type that it will throw
a quantity of light to the ceiling, and a floor or table
lamp for local light.

LIGHT IN THE HOME

FIG. 42. — Carefully shaded wall brackets at face height on both sides of the
bathroom mirror constitute very satisfactory lighting.

LIGHTING THE ROOMS OF THE HOME 125

A totally enclosing direct-lighting fixture is also
permissible provided the glassware is an efficient trans-
mitter and diffuser of the light. The " day light"
lamp is recommended here. The sewing ma<!hine,
preferably located near the window, should be equipped
with a small attached lamp to give light where most
needed — at the needle point — for dark days or evening.

Basement.

An enclosing glass unit, similar to the kitchen unit,
controlled from the head of the stairs, can often be
so placed as to light both the furnace and the stairway.
A 100-watt lamp will be sufficient in such a unit. The
fruit-storage room and coal bin should have their own
lamps (60-watt size).

The lighting of the laundry should be given its rightful
consideration, for the very thorough and careful work
which must be done there needs every lighting advantage.
Since the light from daylight lamps is of such a color
quality as to render dirt and scorches readily apparent,
these lamps are recommended for laundry use. Two
enclosing globes, each fitted with a 150-watt daylight
lamp, are needed to perform adequate service. One
should be hung directly over the tubs and the second
directly over the ironing location.

The work bench can be satisfactorily lighted by such
an enclosing glass globe mounted at the ceiling and far
enough from the wall so that work clamped in the vise
will not be in shadow. This will usually be about 3
feet. A 100-watt lamp should be used. If the bench
is more than 6 feet long, two such units are very desirable.

The recreation room, which is usually long, narrow,
and low-ceilinged, is best equipped with two shallow,
enclosing ceiling fixtures (100 watts each) hung close
to the ceiling or preferably recessed in it. Due to the
prevalence of low ceilings, semi-indirect wall brackets
can also serve equally well. Suitably decorative wall

126

LIGHT IN THE HOME

LIGHTING THE ROOMS OF THE HOME 127

brackets add atmosphere, and if the room is used fre-
quently as a card room, one or two of the indirect
floor lamps will prove indispensable.

Garage.

An economical and efficient means of lighting the
garage is by an RLM standard dome reflector with
a 150-watt lamp, mounted at the ceiling, just over
the hood of the car, possibly hung from a horizontal
suspension wire across the garage, so that it may be
slipped back and forth, wherever desired. In the double
garage, each car space is individually equipped in this
manner and a third outlet is added between and at
the rear of the cars.

DICTIONARY OF ILLUMINATION TERMS

Absorption.

The loss which results when light strikes any object or
traverses any medium.

Reflection J

The lost, or absorbed, light is converted
to heat, raising the temperature of the interfer-
ing body or medium. The percentage of
incident radiation absorbed depends upon
Wave length of the radiation and the
nature of the interfering object; density,
opacity, physical structure, and surface smoothness being
controlling factors.

The amount of light absorbed, expressed as a percentage of
the total amount striking the object or medium, is known as
the absorption factor.

Adaptation.

The adjustment of the eye according to the brightness of the
field of view. This adaptation is accomplished
iris of £ye by the opening or closing of the iris.

Adapted To

Brightness.

M™s;fy

™ Any object emitting or reflecting light is

said to be bright and, through the fact of its
brightness, is visible. Used in this sense, the term " bright"
is purely qualitative, and, in order to fix the brightness of
objects for comparison purposes, a quantitative scale is
necessary.

To supply such a quantitative scale, the brightness of a
surface when viewed in any direction is considered to be the
ratio of the luminous intensity or flux — either emitted or
reflected — expressed in candlepower or lumens measured in
that direction, to the area of this surface projected on a plane
perpendicular to the direction considered.

129

130

LIGHT IN THE HOME

The brightness of a surface is always expressed in terms of
luminous intensity per unit of projected area. The units^used
to define it are the lambert, millilambert, foot-lambert, candle-
power per square inch, candlepower per square centimeter,
apparent foot-candle, and the lux. (See definitions of these
terms.)

CONVERSION FACTORS FOR VARIOUS BRIGHTNESS VALUES

Candles
per
Square
Centi-
meter

Candles
per
Square
Inch

Lam-
berts

Milli-
lamberts

Foot-
Candles

Lux

Candles per

square

centime-

ter
Candles per

6.452

3.14

3,141.6

2,918

31,416

square
inch
Lamberts

0.155
0.318

1
2.054

0.4867
1

486.7
1,000

452
929.03

4,867
10,000

Millilam-

berts ....

0.000318

0.002054

0.001

0.929

Foot-can-

dles
Lux

0.000343
0.0000318

0.00221
0.0002054

0.00108
0.0001

1.076
0.1

1
0.0929

10.76
1

* Values in units in column A times conversion factor equal values in
units at top of other columns.

Brightness is independent of distance — which means that
no matter at what distance from a light source, or other
bright object, an observer places himself, it will appear always
of the same brightness. The explanation for this lies in the
fact that while the total quantity of light entering the eye
varies inversely as the square of the distance between
the observer and the object, the area of the image formed
by the object on the retina of the eye varies in like pro-
portion, so the intensity of this image remains constant. In
other words, the brightness of the retinal image is always
the same.

DICTIONARY OF TERMS 131

Candle.

In illumination practice the word candle refers to the
international candle, which is the unit of luminous intensity
and which resulted in the year 1909 from agreements effected
between the three national standardizing laboratories of
France, Great Britain, and the United States.

Since that time this unit has been maintained by means
of standard incandescent lamps in these laboratories.

Color of Light.

The subjective analysis or evaluation by the eye as to the
particular part of the spectrum in which certain light or
luminous flux belongs. Color can be expressed in terms of its
hue, saturation and brightness.

Cove Lighting.

A system of indirect lighting in which lamps and reflectors
are concealed by a molding or other suitable
cove LI htin structural element around the edge of the
area to be illuminated. The light is directed
to the ceiling, from which it is diffusely
reflected.

Diffusion.

The scattering of light rays so that they travel in different
cross directions rather than in parallel or radiating lines.
Sunlight, in passing through the earth's atmosphere, is more
or less diffused by the particles of dust and moisture, so that
the entire sky appears to be a source of light and the light
from the sky, entering a window, is spread throughout the
room without striations. strong contrasts, or

Diffuse Reflection &

from Rough Mat Surface dense shadows. This sort of effect is known
as diffuse, or diffused, illumination. Due to
the cross light the shadows are luminous, soft,
and free from harshness, while, because of the
large size of the source, a considerable amount

of light may be received without the source appearing bright

enough to produce objectionable glare.

Artificial lighting may be rendered diffuse by various means,

of which the following are some of the more important:

132 LIGHT IN THE HOME

Diffusing bulb, in which a frosting or coating makes
the lamp bulb translucent, so the light appears to come
from its entire area, masking the high brilliancy of the
filament.

The use of several diffusing bulbs in place of a single one
of higher power increases the degree of diffusion.

Diffusing globe, in which opalescent or roughened glass
is interposed between the filament and the eye as so to make
the entire globe appear luminous, with corresponding softness
of shadows. Since globes are larger than lamp bulbs, they
usually produce a higher degree of diffusion.

Diffusing reflector, in which the reflecting surface is
roughened or made of translucent enamel so as to act as a
large secondary light source of low brightness. This type of
reflection is known as diffuse reflection. With indirect and
semi-indirect lighting, a dull white ceiling becomes a very
effective diffusing reflector.

Enclosing Unit.

In the ordinary use of the term a direct-lighting unit in the
form of a diffusing globe entirely surrounding

Enclosing Unit ji

—Fitter

Flame Tint.

.Globe The color designation of a lamp which has
such a coating that it emits light of approxi-
mately the color of the kerosene-oil-lamp flame.

Foot-candle.

The unit of illumination, with the English units as a basis.
It is defined as the illumination at a point 1 foot from a
source emitting 1 candlepower in the direction of the sur-
face. It is the illumination received when 1 lumen of light
falls on 1 square foot of area. A fair idea of the illumination
represented by 1 foot-candle can be obtained by holding
a piece of paper 1 foot away in a horizontal direction from
an ordinary wax candle, or about 5 feet away from an ordinary
25- watt (i.e., 25-candle) lamp.

DICTIONARY OF TERMS 133

Foot-candle Meter.

A small, compact illumination photometer, with a fair

degree of accuracy, about 4 by 8J£ inches in size, weighing 2
screen, .Scale pounds, having a range of from 0.012 foot-
candle to 100 foot-candles. Its principal
advantage is found in its ready portability,
which permits taking readings quickly, and
Rheostat Knob directly in foot-candles, on the work bench,
desk, etc. Its simplicity of construction and of operation makes
it especially desirable for inexperienced persons.

Illumination.

In general, the visual sensation produced when radiant
flux within the limits of wave length of so-called visible light,
of sufficient intensity and duration, impinges on the retina.
It is often used synonymously with the term lighting. Spe-
cifically, illumination is sometimes used to designate visible
radiation falling on a surface as distinguished from light
emitted from a source. Its quantitative unit is the foot-
candle.

Intensity.

The power of light emitted in any given direction. It is
measured in candles or apparent candles.

Inverse -square Law.

A general geometric principle applying to light, magnetism,
and other effects which radiate out from a central point and
so become attenuated through being spread over greater
space as the distance from the point increases.
In illuminating engineering this law assumes
a source of light of sufficiently small dimen-
sions as to be considered a point source. For
ordinary calculations, this condition is
assured if the distance from the source to
the point of measurement is at least five
times the maximum diameter of the source. The accuracy is
greater if this factor is larger. If we had a screen, with an
opening 1 inch square cut in it, placed 1 foot from an incandes-

134 LIGHT IN THE HOME

cent lamp, it is obvious that the light passing through this
opening and falling on a second screen at 2 feet from the
light source would give a spot 2 inches square, or 4 square
inches; at 3 feet, 3 inches square, or 9 square inches; etc. In
other words, as the beam travels away from the lamp it is
spread over an area which increases with the square of the
distance. Obviously, the same flux spread over a larger area
correspondingly reduces the illumination.

The law of inverse squares does not take into account any
absorption of light by the atmosphere, smoke, or any other
medium. It does not apply to parallel light nor to light sources
of large dimensions, as can be shown by repeating the above
experiment.

This law of inverse squares is made use of in photometry
and in theoretical calculations. It was formerly used exten-
sively in predicting the illumination provided by lighting
installations, but, because of the arduous calculations involved
and the difficulty in evaluating the light added by reflection
from ceiling and walls, it has given way for such purposes to the
simpler flux-of-light method, q. v.

Lambert.

The average brightness of any surface, or the uniform
brightness of a perfectly diffusing surface, emitting or reflecting
1 lumen per square centimeter.

For most purposes the millilambert (0.001 lambert) is the
preferable practical unit for evaluating the brightness of
illuminated surfaces. (See Brightness.)

Light.

The term light is used in various ways:

a. To express the visual sensation produced normally
when radiant flux, within the proper limits of wave
length, of sufficient intensity and duration impinges on the
retina.

6. To denote the luminous flux which produces the sensation.

c. Often in common parlance the word light is applied
to wave lengths outside the visible spectrum (ultraviolet
light). A better term is, of course, ultraviolet radiation.

DICTIONARY OF TERMS 135

Lumen.

The unit of luminous flux: the amount of light (1) emitted
over a given solid angle around a source or (2) received on a
given area. It differs from the candle or foot-candle in that it
takes account of the extent of space or area over which the
light is distributed. It is obvious that for a given illumination
the flux or amount of light (lumens) varies directly with the
area over which this illumination is distributed. Whether
representing light sent out by a source or received by a surface,
a lumen represents the same amount of light.

Lux.

The practical unit of illumination, using the metric system
of measurement, the illumination of a surface 1 square meter
in area receiving an evenly distributed flux of 1 lumen, or
the illumination produced at the surface of a sphere having
a radius of 1 meter by a uniform point source of 1 inter-
national candle situated at its center. Since 1 square meter is
equal to 10.76 square feet, 1 foot-candle is equal to 10.76 lux.
This unit is used in France and other countries where building
dimensions are given in meters.

Mat or Matte Surface.

Any surface which scatters completely light falling on it
so that the surface appears of almost equal brightness, no
matter from what direction it is viewed. (For illustration see
Diffuse Reflection.)

Opaque.

Impervious to light rays. The quality of an object or
material that prevents the transmission of light. This quality
as regards materials is relative; for example, gold is ordinarily
regarded as opaque but in very thin sheets becomes trans-
lucent. Conversely, certain materials ordinarily regarded as
transparent or translucent, if sufficiently thick, become
opaque. It is therefore common in speaking of materials to
refer to the degree of opacity somewhat as a reciprocal
of transmission.

136 LIGHT IN THE HOME

Photometer.

An instrument used for measuring light intensities; Briefly,

it is an incandescent lamp the candlepower of which is known

and calibrated with respect to a scale of foot-candle values

marked on the photometer. The light from this lamp is then

balanced on a photometric screen with that

The human eye has the power of recognizing
ecluatity of brightness on adjacent fields, the
degree of accuracy depending upon the
similarity of colors . In obtaining the balance,
the illumination received from one or both of
the light sources is varied by changing the relative distances
or by other means until equality of brightness is obtained.
The candlepower of the unknown source can then be calculated
or read directly from a scale provided for the purpose.

Photometers take a variety of forms, the distinguishing
feature being a balance of accuracy against portability. The
least portable are, obviously, the most accurate, and vice
versa. Lamps used for such purposes are known as photo-
metric standards.

Reflection.

The light flux striking an object which is turned back (i.e.,
is neither transmitted nor absorbed).

Light striking any object will be absorbed, transmitted,
or reflected. No object will perform any one of these opera-
tions perfectly, the practical condition being that most
objects both absorb and reflect the light incident upon them,
while many objects perform all three operations, in that they
partially reflect, absorb, and transmit the incident light.

The percentage of incident light reflected by an object is
called its reflection factor and is used as a criterion of the
reflectivity of that particular object.

The degree to which an object receiving light upon its
surface can reflect it is called its reflectivity.

Spectrum.

The arrangement of colors in order of wave length produced
when a beam of light is refracted by a prism or diffraction

DICTIONARY OF TERMS

137

Electromagnetic Series
Wave Length Kind of

Millimeters Radiation

40,000,000.0-*^

30000.0-

20.0-

0.000,7..
0.000,3---^
0.000,03—* =
0.000,001-— =

VeryShort
Electric Waves
(notused)

Infra-Re^
Rays

VisibleLight
Ultra-Violet
X-ffays

Rays

grating. Of the visible rays, the violets or short-wave rays

are bent (or refracted) most, and the red or long-wave rays
are bent least. The order of colors is red,
orange, yellow, green, blue, violet.

In the prismatic spectrum, or that pro-
duced by a prism, the red and yellow bands
are relatively wider and the blue and violet
bands relatively narrower than in the diffrac-
tion spectrum which is produced by a
diffraction grating.

In reality, the spectrum extends in both
directions beyond the visible spectrum, which
has been defined above. The invisible
radiations beyond the violet end of the
visible spectrum are known as ultraviolet or

chemical rays. Those beyond the red end are commonly

known as infra-red or heat rays.

Spread Reflection.

The manner in which light is reflected when it falls on a
slightly roughened mirror surface, such as matt aluminum.
The reflected light has the same general direc-
tion as if the law of regular reflection held,
yet the roughened surface introduces a certain
amount of diffusion. This has the effect of
making the reflected beam of considerably
greater spread and, of course, reduced maxi-
mum intensity.

Translucent.

The characteristic of an object which permits light to
pass through it and yet, unlike a transparent object, diffuses
the light so as to break up images. For example, opal or
frosted glass.

Transmission.

The passage of light through an object or medium. It
may be said that all substances, no matter what their density
may be, will, if made thin enough, transmit light to some
degree. The ratio of transmitted light to incident light is

Spread Reflection

from semi -Mat surface

Angle of Incidence -Angleaf 'Reflection

138 LIGHT IN THE HOME

known as the transmission factor of an object, or of a material
of specified thickness.

Ultraviolet Radiation.

Invisible radiation of slightly shorter wave lengths than
those of the violet light. Its characteristics are evidenced
through actinic properties as well as the producing of the
effect of so-called sunburn on the skin.

Because of their effect on photographic plates, and in con-
nection with other chemical reactions, ultraviolet^rays are
sometimes called chemical rays. Certain of these radiations
have power to injure the eye seriously; on the other hand,
properly employed therapeutically they have beneficial
physiological effects related to the production of vitamines.
Quartz is transparent to all but the shortest wave lengths of
ultraviolet light. Ordinary glass is practically opaque to
such radiation. The absence of ultraviolet radiation is the
cause of rickets in human beings and "weak legs" in chickens.

QUESTIONS
Chapter I

1. Name the various light sources utilized previous to the

incandescent lamp.

2. Who was responsible for the invention of the first com-

mercially practical incandescent lamp? At what date?

3. What practical applications has the photoelectric tube?

4. What are some of the possible far-reaching effects attrib-

utable to defective vision?

5. What lighting conditions are largely responsible for eye

strain?

6. What radiations are particularly effective in health main-

tenance?

7. What is the single possible harmful effect of overdoses of

safe ultraviolet radiation?

Chapter II

1. What means are we afforded to secure soft and comfortable

lighting?

2. What creates annoying reflections from paper (book,

magazine, and writing)? Name ways of avoiding and
eliminating this disturbing condition.

3. Why are dark-finished paneled rooms difficult to light

comfortably?

4. Explain the importance of the position of the light source.

5. Why is a light-colored inner surface of a lamp shade so

much more desirable than a dark one?

6. Why are several portable lamps and a ceiling fixture a

happy lighting combination for a living room?

7. Discuss glare in relation to amount of light.

8. Discuss the prevalence of defective vision.

Chapter III

1. What is incandescence?

2. The ratio of what two terms forms the unit of measure for

lamp efficiency?

139

140 LIGHT IN THE HOME

3. What causes a lamp to burn out? To blacken?

4. What advantages accrue to the user of gas-filled lamps?

5. Why are lamps having frosted bulbs preferable to those

having clear bulbs? How do they compare in effi-
ciency?

6. What is the daylight lamp (bulb)?

7. What is the average lamp life of a standard lamp with

an A bulb; a G bulb; an F bulb?

8. What is the disadvantage of burning a lamp at a voltage

higher than its rated voltage; lower than its rated
voltage?

9. What constitutes quality in a lamp?

10. Why is it not economical to buy cheaper lamps of poor
quality?

Chapter IV

1. What does the rainbow reveal about the composition of

sunlight?

2. How can three surfaces, with three shades of grayness,

be made to appear alike?

3. Explain how white light reveals the color of objects.

4. Why do mixtures of yellow and blue pigments appear

green when illuminated with white light?

5. Name the three subtractive primaries; the additive

primaries.

6. Why when a red medium is placed around a light source

is the resulting light red?

7. What three colors of light are needed to produce practi-

cally all of the spectral colors?

8. Name the colors resulting from two-color mixtures of the

additive primaries. What relation exists between the
three colors so produced and the subtractive primaries?

9. What four factors influence the apparent color of a surface?

10. Name the emotional value of the principal colors.

11. Name color appearance of red, green and blue objects

when illuminated with red, yellow, blue and purple
light respectively.

12. Discuss the usableness of colored and of tinted light in the

home.

QUESTIONS 141

Chapter V

1. What materials are good conductors; poor conductors;

insulators?

2. What is the unit of measurement of rate of flow of elec-

tricity; of electromotive force; of resistance? What
is their relationship?

3. When is a circuit open; when closed? Explain a short

circuit.

4. What is a series circuit; a parallel circuit? With eight

lamps of equal resistance connected in series to a 120-volt
source, what is the voltage applied to each lamp?

5. What electrical terms are involved in measuring power?

What is their relationship?

6. At a 6-cent rate, calculate the cost of operating the following :

a. A 200-watt lamp for 3 hours.

b. Heater, 700 watts, 6 minutes.

c. Table lamp, two 60-watt lamps, 3^ hours.

d. Kitchen unit, 100 watts, 2^ hours.

Chapter VI

1. What is the purpose of a fuse?

2. What is the purpose of the Electrical Code of the National

Board of Fire Underwriters?

3. Explain the four principal systems of wiring.

4. What are lighting branch circuits; ordinary appliance

branch circuits; medium-duty appliance branch circuits?

5. What is accomplished when No. 12 wire is used for branch

circuits?

6. At what height and in what position is it advisable to

place wall brackets, both decorative and utilitarian?

7. a. When are three-way switches employed?

b. When is the symbol S-4 required?

c. Is there any limit to the number of switches which can

be employed to control a single outlet?

8. What simple guides have we for the placing of convenience

outlets?

9. Why is it advisable to place the convenience outlets of a

room on a separate circuit from the fixtures?
10. What is the function of a master switch?

142 LIGHT IN THE HOME

Chapter VII

1. Why is it more necessary to shade carefully our present

illuminant (the incandescent lamp) than previous
sources of light?

2. Name the three systems of lighting and the characteristics

of each.

3. In selecting the lighting equipment for a given home, what

factors, aside from personal taste, should be considered?

4. In what three types does home-lighting equipment divide

itself?

5. What factors determine the type of ceiling fixture selected ;

of wall bracket?

6. What purposes do correct shades serve? What char-

acteristics should they exhibit?

7. What causes the depreciation in the amount of light

produced by lighting equipment? What is the simple
remedy for this?

Chapter VIII

1. What is the goal of good lighting in the home?

2. What broad lighting principles must be incorporated to

obtain good lighting?

3. What determines the lamp wattage in any given equip-

ment?

4. What functions should entrance lighting perform?

5. What are the advantages of a ceiling fixture in the living

room?

6. Why are open-top lamp shades generally desirable?

7. What suggestions would you make for lighting a secretary;

a davenport; a telephone table; a reading chair; a
piano?

8. Discuss the various methods of lighting the dining room.

9. What is the standard recipe for kitchen lighting?

10. What are the lighting requirements, and how are these

attained, at a dressing table; in a child's bedroom?

11. How should light at the bathroom mirror be provided?

When is a ceiling fixture there desirable?

12. What kind of lighting does a sewing room require?

13. How should the laundry be lighted; the garage?

INDEX

Absorption, definition of, 129
Adaptation, definition of, 129
Armored cable, wiring method, 58

Basements, lighting of, 125, 126
Bathrooms, lighting of, 123, 124
Bedrooms, lighting of, 117
Branch circuits, wire sizes, 60, 62

wiring for home, 58
Brightness, definition of, 129

Candle, definition of, 131
Carbon lamps, 28
Carrying capacity of wires, tabu-
lation of, 61
Ceiling fixtures, cost, 92

historical changes, 78

maintenance of, 87

mechanical and electrical con-
struction, 91

modern trends, 80

rating of, 88

shades for, 81

specifications for, 88

types in use, 77, 79
Cellars, lighting of, 125, 126
Childrens' rooms, lighting of, 121
Circuits, electrical, 47
Closets, lighting of, 122, 123
Coefficient of reflection, 19
Color, light and, 31, 34, 35, 131

primaries, 36

symbolism of, 39

Colored light, additive and sub-
tractive primaries, 36

discussion of, 34, 131

mixtures, 35

use of, 41

Conductors, electrical, 45
Conduit, wiring method, 58
Convenience outlets, wiring and

location, 70
Cove lighting, definition of, 131

"Daylight" lamps, 27
Development of lighting, 1, 2
Dictionary of illumination terms,

129

Diffusion, definition of, 131
Dining rooms, lighting of, 111
Dressing table, lighting of, 119
Dual-purpose lighting, 8

Early development of light sources

1,2
Efficiency of incandescent lamps,

23
Electricity, circuits, 47

conductors and insulators, 45

cost of power, 52

fundamentals of, 44

historical, 44

measurement of power, 49, 50

units of measurement, 46
Entrances, lighting of, 94
Eyesight, adaptation, 129

effect of light on, 6

size of light source and relation
to, 11

143

144

LIGHT IN THE HOME

Fixtures, cost of, 92

development of, 78

maintenance of, 87

mechanical and electrical con-
struction, 91

modern trends in, 80

rating of, 88

shades for, 81

specifications for, 88

types used, 76, 77, 79, 81, 83
Foot-candle, definition of, 132
Foot-candle meter, description, 133
Fundamentals, of electricity, 44

of lighting, 11, 17, 74

Garages, lighting of, 127
Glare, deleterious effects of, 20

Hallways, lighting of, 96
Health, relation of good lighting
to, 8

Illumination terms, definitions of,

129

Impaired vision, causes of, 7
Incandescence, 22
Incandescent lamps, applications
of, 29

bases, 26

carbon, 28

characteristics of, 22

cost of operation, 52

daylight lamps, 27

development of, 3

efficiency, 23

frosting, 26

life, 27

shapes and sizes, 25

vacuum and gas-filled, 24

voltage, 27

Insulators, electrical, 45
Inverse-square law, explanation
of, 133

Kitchens, lighting of, 116, 117
Knob and tube, wiring method, 57

Lambert, definition of, 134
Life of incandescent lamps, 27
Light and color, additive and sub-
tractive primaries, 36
colored light mixtures, 35, 131
contrasts in, 39
pigments, 32

spectral composition, 31, 131
symbolism of, 39
use of, 41
Light sources, characteristics of,

development of, 2
importance of shading, 20, 74
operating cost, 52
position of, 17, 74
size of, 11
Lighting, equipment for, 74, 76, 81,

fixtures, 76, 77, 79, 81
fundamentals of, 11,17, 74
rooms of home, 93-127
shades, 81
specifications, 88
systems of, 75
wiring for, 53

Lighting equipment, cost, 92
fixtures, 76, 77, 79, 81, 83
light source, 74
maintenance of, 87
mechanical and electrical con-
struction, 91
obsolescence, 77
rating of, 88
shades for, 81
specifications for, 88
systems, 75

INDEX

145

Living rooms, lighting of, 98
Lumen, definition of, 135
Lux, definition of, 135

Maintenance of lighting equip-
ment, importance of, 87
Measurement of electricity, 46, 49

Non-metallic-sheathed cable, wir-
ing method, 57

Photoelectric tube, uses of, 4, 5
Photometer, description of, 136
Pigments, discussion of, 32
Plans, house wiring, 63-65
Portable lamps, maintenace of, 87

requirements for, 83

types in use, 84, 85
Power, measurement of, 49, 50
Primary colors, discussion of, 36

Quantity of light versus glare, 20
Questions, list of, 139

Rating of lighting equipment,

specifications for, 88
Reflection factors, 19

Safety enhanced by light, 5
Sewing rooms, lighting of, 123
Shading of light sources, impor-
tance of, 11

Shapes and sizes of bulbs, 25
Specifications for evaluating light-
ing equipment, application
of, 88

Spectrum, explanation of, 136
Switches, wall, wiring for, 69
Symbols, wiring, 67

Ultraviolet radiation, composition

of, 138
effect on health, 8

Vacuum and gas-filled lamps, 24
Vision, adaptation, 129

effect of light on, 6

glare, 20

size of light source, 11
Voltage, importance of proper
maintenance, 27, 60, 61

relation of wire size to, 61, 62

Wall brackets, types of, 82

use of, 81

Wall switches, wiring for, 69
Watt-hour meter, description of,
50

installation of, 55

reading of, 51
Wires, carrying capacity, 61, 62

sizes for residence use, 60
Wiring, branch circuits, 58

convenience outlets, 70

electrical circuits, 53

equipment necessary, 54

floor outlets, 71

future provisions, 72

layouts, 63-65

methods in use, 56

requirements for, 53

special considerations, 72

symbols, 67

wall switches, 69

wire sizes, 60, 62

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