The Forest Products Laboratory : a brief account of its work and aims

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scientific knowledge, policies, or practices.

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FOREST SERVICE - UNITED STATES DEPARTMENT OF AGRICULTURE
MISCELLANEOUS PUBLICATION NO. 306 - 1938

THE
FOREST PRODUCTS
LABORATORY

A BRIEF ACCOUNT OF

ITS WORK AND AIMS

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SD Ey ART VWoEyN hw Or AGRI CULT URE

MISCELLANEOUS PU BiahCA TT 1ON NO. 306

UNITED STATES GOVERNMENT PRINTING OFFICE -«- WASHINGTON . 1938

For sale by the Superintendent of Documents, Washington, D. C. Price 15 cents

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A NATIONAL INSTITUTION
FOR WOOD UTILIZATION RESEARCH

) Tue Forrest Propucts Lasora-

TORY Is a unit of the research or-
ganization of the Forest Service, United
States Department of Agriculture. It
is the only institution in the United
States concerned wholly with the in-
vestigation of wood and wood products
and their adaptation to diversified fields
of use. It was the first and for several
years the only institution in the world
conducting general research on wood
and its utilization; other Governments
have since followed the lead of the
United States in developing labora-
tories along similar lines.

Importance of
wood utilization

The forest, distinct from all its other
services and. benefits, supphes a basic
raw material—wood—which from the
earliest times has furnished mankind

with necessities of existence and with
comforts and conveniences beyond
number. Forests will return maximum
values to the people of the United
States, only if they are fully and profit-
ably utilized and at the same time are
maintained in vigorous condition for
the continuous production of timber
crops.

Nearly one-third of the continental
United States is either in forest or suited
by nature mainly or solely to the grow-
ing of forests. In a broad sense, the
erowing of forests appears to be the
only economic use to which this enor-
mous area, amounting to over 600 mil-
lion acres, can be put. The fullest
development of this use is of profound
importance to the country’s prosperity.
Aside from providing timber, forested
land affords benefits of far-reaching 1m-
portance, through its favorable influence
on stream flow atid in preventing exces-

The perpetuation of forest resources and their proper utilization are essential

to the country’s welfare.

M-14925-F

M-—14192-F

Employment and wages for thousands of workers are bound up with continued and
increasing usefulness of wood in modern life.

sive erosion, in providing shelter and
protection for homes, crops, and live-
stock against wind and drought, in pro-
viding forage, in supplying recreational
needs, and in furnishing the environ-
mental conditions upon which wildlife
of the country depends. In addition it
is desirable that a reasonable area of
forested land be reserved in its virgin
condition for scientific and recreational
use. All these benefits, though not easily
appraised, in the aggregate represent
ereat values to the public.

While the growing of timber on these
lands for the many products demanded
by modern civilization represents the
more tangible economic value or use,
the mere production of an increased
timber supply does not satisfy the de-
mands of economic forestry. The util-

2

ity value of wood must also be main-
tained and increased. From this stand-
point the actual and potential value of
these lands as a source of wealth and
employment must be gaged in a large
measure by the utility value of this prin-
cipal product. The better adaptation
of wood to modern consumption re-
quirements is a matter of direct concern
to consumers, whose proper housing and
standards of living are bound up with
the satisfactory use of wood products;
to workmen, who need the hundreds of
millions of dollars in wages furnished by
employment in the woods, the sawmil

the pulp mills, and broadly diversified
fields of wood construction and manu-
facture; to farmers and other timber-
land owners, large and small, seeking
market outlets for materials from their

tli

M-—31281—F

Improved timber harvesting and utilization methods mean increased income to farmers,
whose woodland holdings throughout the country amount to 185 million acres.

vast ageregate acreage of woodlands; to
local communities, counties, States, and
the Nation, all of which have a vital in-
terest in stable revenues from forests,
forest lands, and successful forest indus-
tries. In our national forests alone, the
investment in land and timber and the
responsibility for a wise utilization of
the products require a broad program of
research looking to the broadening and
stabilization of markets for forest
products.

Purpose of
Laboratory research

Answering to these major economic
needs, the research of the Forest Prod-
ucts Laboratory is directed toward the
better and more efficient and diversified
utilization of forest materials. Scien-
tific research is the means that must be
used to gain a more thorough knowledge
of wood in its chemistry, growth, and
structure, and to determine the techni-

America’s huge volumes of logging and sawmill wastes are potential sources of

useful products.

M-S7-F, M-—31511-F

cal properties of the hundreds of Ameri-
can wood species and their variations
of quality within the stand and in the
tree itself. Research must aid in solv-
ing many difficult problems—how to
utilize more efficiently the small-sized
and second-growth trees which will
form the bulk of our future forests;
how to secure useful service from the
many wood species that are now used
httle if at all; how to turn to economic
account the large wastes that occur in
the conversion of trees into commodi-
ties; how to secure greater service and
economy from wood through selection
of material, control and modification of
its properties, improvement of treating
processes, and the development of new
and better methods of wood fabrication
and conversion.

Cooperation
with University

The Forest Products Laboratory was
established by the Forest Service in
Madison, Wis., in 1910, following ac-

4

M-26224—F
Laboratory utility building of plywood with glued arches, the first structure of this type
in the United States.

ceptance of the offer of the University
of Wisconsin to provide a building with
necessary light, heat, and power serv-
ices. This arrangement made possible
the coordination and systematic de-
velopment of Forest Service research
activities that had previously been car-
ried on in a number of small labora-
tories in various parts of the country.
A cooperative relationship between the
Laboratory and the University of
Wisconsin was thus begun which has
continued to the present, assuring
collaboration in scientific matters and
interchange of research facilities for staff
and graduate students. The original
building was occupied by the Labora-
tory for 20 years, and additional tem-
porary quarters were provided by the
university as increasing work required.

Present building €

In 1930 the long-felt need of adequate
permanent quarters for the Laboratory
was recognized by Congress and con-
struction funds were granted. The

present main building was completed in
1932, representing with later additions
to its equipment an investment of well
over $1,500,000. The fine site of 10
acres on which it stands, overlooking
the city and Lake Mendota, was pro-
vided by the State of Wisconsin through

1e board of regents of the university.

In general plan the main building is
U-shaped, about 275 feet in length and
over-all breadth, with wings flanking a
central court. In its five stories and
eround floor it contains a total area of
175,000 square feet, or approximately
4 acres. The Laboratory is provided
with plant facilities and experimental
equipment suited to the handling, proc
essing, testing, and investigation of
wood in many forms, from the raw
material of the log to lumber, pulp,
paper, turpentine, plastics, and other
conversion products.

Accessory structures

Several minor structures on the
Laboratory’s grounds have been pro-
vided for operating or demonstrational
purposes. Among these are a receiving
and utility building of plywood units
framed on glued laminated wood arches,
a concrete fire-testing house, a veneer-
cutting plant, and open and closed
sheds for lumber storage.

Personnel and
research divisions

The personnel of the institution is
divided about equally into technical
staff, comprising research specialists and
assistants, and nontechnical staff, in-
cluding administrative, operating, and
clerical workers. The entire organiza-
tion centers around and is contributory
to the work of eight research divisions,

In many investigations the Laboratory’s sawmill plays a necessary pari.

M-—27318—-F

whose fields of investigation are de-
scribed in the following pages—timber
harvesting and conversicn; silvicultural
relations; chemistry, composition, and
derived products of wood; timber me-

TIMBER HARVESTING

chanics and structural research; wood
seasoning and moisture control; wood-
treating processes for protection and
service; wood pathology; and pulp and
paper.

AND CONVERSION

TurouGH hasty and wasteful exploita-
tion, millions of acres of forest lands
have been left denuded, idle, and
abandoned which otherwise might to-
day be supporting their quota of pros-
perous communities. To obtain better
values from existing resources and to
safeguard future timber crops require
basic changes In timber cutting and

conversion practice, presenting many
problems which research must help to
solve.

Selective logging

Laboratory field crews have demon-
strated on many lumbering operations,
north and south, that the cutting of

Turning of wooden turpentine cups points the way to profitable utilization of
much worked-out timber.

M-—27617—-F

young and undersized trees ranging
from 10 to 16 inches in diameter, ac-
cording to the stand, is destructive not
only of future forest values but actually
of present profits, since the small trees
do not yield enough high-quality lum-
Mer to repay costs of handling and man-
ufacture. By selective cutting, taking
only the larger trees and leaving the
smaller trees to grow, better lumber is
produced and a basis is maintained for
profitable timber crops in the future.
The findings are beginning to be ap-
plied in the practice of both large and
small operators, with increasing pros-
pects of restocking and reseeding of
stands, repeated cuttings, and the eco-
nomic benefits arising from sustained
forest productivity. The studies need
to be extended to a wider range of tim-
ber types and to the production of com-
modities other than standard lumber.

Reduction of waste

Research projects to reduce the per-
centage of waste in harvesting the forest
crop approach the problem from sev-
eral directions—the use of less destruc-
tive machinery, the conversion of woods
and mill waste into useful products, and
profitable alteration of the form of the
product. The production of dimension
stock cut to size for factory use makes
possible the salvaging of a large volume
of clear material from slabs, edgings,
and defective lumber. Saving in freight
on waste, and reduction of cutting re-
quired in the factory, have proved to be
Important factors in reduction of costs
to the user. The further development
of methods for producing high-quality
dimension stock, including its sawing,
seasoning, and bundling, is under in-
vestigation.

M-—30569-F
Development of lightweight power equip-
ment brings nearer the economic possibility
of pruning branches and securing growth of
wood free of knots earlier in the life
of the tree.

Farm woodlands
and small holdings

To make possible the production of
better lumber by the farm community,
a new type of portable sawmill with
band saw is under development, and
an economical and effective small dry
kiln has been designed and tested. Ex-
periments are being made in the use of
small material for the production of

7

glued laminated building panels and
other commodities for local and general
markets. Selective logging investiga-
tions and the development of portable
power pruning equipment offer to the
small owner possibilities of early and
sustained yield of merchantable lumber
from his holdings. The turning of gum-
collecting cups from southern pine trees
that have been ‘worked out” in turpen-
tining operations indicates the possibil-
ity of replacing metal cups, at a con-
siderable saving to woods owners. Util-
ization of the worked-out timber for
rosin barrels and for fruit and vegetable
crates is also being studied.

Machining studies

Many American hardwoods, particu-
larly those from the lowlands and river
bottoms, are rejected by users on ac-
count of difficulties in seasoning and
woodworking. To aid in converting

M-—26966-F
Woodworking tests determine machining
qualities of woods now little used.

such material from a lability to an
asset, a broad program of research is
maintained. In addition to chemical
seasoning, studies of typical machining
operations are carried on together with
investigations of physical and mechan-
ical properties of the woods and their
adaptability to varied commercial uses
such as furniture, automobile bodies,
and food containers.

Measuring power required in boring various woods affords one index of
woodworking properties.

M-—26772—-F

SILVICULTURAL RELATIONS

IN ANY EFFORT to increase the utiliza-
tion value of wood, testing and selection
ssume essential and immediate impor-
tance. Fundamental, however, to the
general program of forestry and wood
use 1s the problem of control of wood
quality atits source. Its solution must
be found in the conditions of tree
growth, and at this point the research
of the Laboratory makes close contact
with silvicultural experiments and prac-
tices in the field.

Growth and quality
of wood

The wide variations in strength, hard-
ness, shrinkage, and other properties of
wood produced within a tree species as
a result of growth under different con-
ditions have prompted the Laboratory
to investigate the possibilities of im-
proving wood quality at the source,
that is, while the tree is growing.
Wood grown under different natural
conditions or under conditions artifi-
cially modified with respect to soil,
moisture, density of stand, and asso-
ciated species, is tested and compared
in order to find the best conditions to
produce the best type of wood for given
uses. Although many years are re-
quired to grow trees of merchantable
size, a change in growth conditions,
such as may be effected by removal of

neighboring trees, drainage, or pruning,
}. reflected in the character of the an-
nual growth rings subsequently formed,
thus affording a ready means of com-
paring wood before and after the change
was made, the other variables remain-
ing unchanged. The resulting infor-

mation can be beneficially applied to
second-growth timber which is still in
the formative stage. For instance,
softwoods make their best development
as to strength and other desirable prop-
erties when spaced moderately close,
whereas the quality of hardwoods is
sustained or improved by increased
opening up of the stand.

Identification

Tamilies, genera, and many individual
species of wood may be identified as
readily by cell and pore arrangement as
by the botanical characteristics of the
tree. The specialized service provided
by the Laboratory in wood identifica-
tion is widely used. About 3,000 sam-
ples per year are identified. Frequently
important questions of use and even

M-29644—F

Width of annual rings and quality of the

wood are correlated with factors of climate
and soil affecting growth of the tree.

9

lawsuits hinge on the result of an ex-
amination of a few chips or shavings,
sawdust, or wood flour. In criminal
cases the careful identification of pieces
of wood may furnish valuable evidence;
an outstanding example was the Labo-
ratory’s discovery of the source of the
wood from which the ladder used in
the Lindbergh kidnaping was made.

Naval stores

A major forest industry of the United
States is the production of gum resin
and turpentine, the naval stores of
commerce, from the longleaf and slash
pines of the South. The United States’
world leadership in output has unfor-
tunately been gained and held at a high
cost in destructive working of stands
and impairment of prospects for future
yields. In research looking to the im-
provement of this situation the Lab-
oratory works in collaboration with the
Southern Forest Experiment Station.
Field tests and microscopic examina-
tion of wound response have shown the
practicability of maintaining the flow
of oleoresin by light, narrow chipping
at as high a yield as by heavy chipping.
The establishment of this fact is having
wide influence in securing a _ longer
working life for turpentine stands, with

10

M-—31575-F

Thousands of wood specimens submitted to
the Laboratory are identified by their micro-
scopic structure.

ereater returns per tree in both naval
stores and wood products.

Biochemical research reveals the
course of formation of the resin-yielding
compounds in the tree; microscopic
research seeks to identify and trace the
occurrence of these mother substances
in the cells of the wood and of the
phloem, orinner bark. Progressin both
lines of investigation encourages the
hope that high-yielding strains may be
further developed in oleoresin-producing
tree species.

ee eee

CHEMISTRY, COMPOSITION, AND

DERIVED PRODUCTS

wl HE FUNDAMENTAL FACTS Of wood as a
Wubstance must ultimately determine
its possibilities as well as its limitations
in use. The chemical composition of
wood, the arrangement of the constit-
uent parts in the wood cells, and the
variation of all such characteristics
according to species and growth con-
ditions are investigated for the aid and
insight they afford in all fields of wood
research—in silvicultural control of the
material and its properties, in its selec-
tion, its seasoning and handling, its
impregnation with preservatives, its use
in construction, and its conversion into
pulp and derivative products of all

types.
Microstructure

All wood is composed of cells, and
visible under higher magnifications are
smaller structural units. These sub-
divisions are being carefully explored.
The cell walls are made up of concentric
layers, which in turn are composed of
fibrils arranged spirally. The fibrils
are the smallest units that become
evident through any simple mechanical
disintegration, but by careful chemical
treatment they themselves may be
subdivided into spindle-shaped fusi-
form bodies and the latter into minute
spherical units. The spherical unit—
oe: ultimate visible component of

he cell wall—is about one hundred-
thousandth of an inch in diameter, and
beyond it the microscope cannot pene-
trate. It is possible, however, by indi-
rect methods using the ultracentrifuge

OF WOOD

and the X-ray, to determine the
approximate size and arrangement of
submicroscopic units.

To the chemist, wood is a storehouse
of raw materials only partially devel-

Top, Cross section of wood, magnified; cen-
ter, cellulose fibers of wood, with lignin re-
moved; bottom, lignin structure of
wood, cellulose removed.

M—2968, M—2960, M—9401—F

oped. It may be analyzed, broadly, as
cellulose and lignin, with extractives or
infiltrated substances such as resins,
gums, tannins, waxes, or the like present
to a greater or less extent.

Cellulese

Cellulose, the most abundant con-
stituent of wood, is also the best known
and the most extensively developed in
commercial processes. It includes the
cottonlike substance of the fiber, which
is the basis of refined paper pulps and

M-—8534-F, M-—7931—F

Wood fiber structure: Top, Concentric layers
structure

of the cell wall; bottom, ‘‘sleeve’
revealed by endwise slippage.

12

the modern family of products includa-
ing rayon, lacquers, cellophane, photo-
eraphic films, gunpowder, and a long
list of nitrate and acetate plastics.
This cellulose, although closely related
to the simple sugar, glucose, is because
of its complex molecular structur
extremely stable. It is known to exist’
principally in the fibrils of the cell
wall, but there is associated with it a
less stable group of materials amount-
ing to almost 40 percent of the total
carbohydrate content of the wood and
containing pentose sugars and uronic

M-—10296—-F (B6), M—10330—-F (F1)

Wood fiber structure: Top, Filamentlike
winding on outer wall of fiber; bottom, the
filament removed, showing convolutions.

t

acids. The Laboratory’s studies aim
at characterizing the less stable bodies
accurately and devising treatments that
will include them in useful products
along with the stable cellulose. Special
possibilities in cellulose conversion are

ffered by hydrolysis and fermentation

“with yeasts or bacteria, which the

Laboratory has already successfully
used in the production of industrial
alcohol, acetic acid, and lactic acid from
wood.

Lignin

Next to cellulose, the greatest bulk
constituent of wood is lignin, the
material that surrounds the cellulose
fibers and forms a continuous matrix
or honeycomb throughout the wood.
Lignin has always been considered a
waste in the pulping process and as such
is discarded. Its use is limited by the
fact that its chemical character and
relationships have never been clearly
determined. The attack on this chem-
ical problem is gradually overcoming
obstacles. Special treatments are pro-
ducing lignin apparently free from
degradation products of the cellulose
and showing a recognizable chemical
structure; characteristics of hardwood
and softwood lignins are being more
sharply differentiated; and increasing
knowledge of the material indicates
possibilities of its conversion into useful
products.

Conversion products

Vast increases of forest market values
await the greater development of useful
products from wood waste. The best
opportunities in this direction seem to
be offered by the hydrolysis, condensa-
tion, and fermentation processes and

the development of special pulp prod-
ucts and wood plastics. The fact that
the cell-wall substances of wood are
readily convertible into sugars has led
to the experimental processing of saw-
dust as an ingredient of cattle feed. As
a further example of the utilization of
waste wood, a molding powder of true
plastic propertiesis being developed from
sawdust, in which the condensing and

Top, Wood fibers resolved into their compo-
nent fibrils; center, the fibril subdivided into
fusiform bodies; bottom, spherical units of
cellulose, the smallest components of the
fiber substance visible under the microscope.

M-8617—-F, M-—9053-F, M-—15639—F

M—24640-F
Equipment of industrial type for chemical
wood conversion.

M-—31512-F

Lignin comprises approximately one-fourth
the weight of wood. A waste material at
present, its utilization depends on a better
understanding of its composition and

chemical relationships.

M—25822-F

By simple chemical means sawdust is

changed into a molding compound that

can be formed into sheets or shaped articles
under heat and pressure.

14

M-31510-Fgge
A specimen of wood plastic coming @
from the mold.

adhesive properties of lignin appear to
be the formative agency. By pressing
the processed sawdust under heat, a
sheet material is formed that offers wide
possibilities of use as floor tile, wall-
board, switchboard panels, and a vari-
ety of other products, at a cost per
square foot estimated to be equivalent
to the general price level of lumber.

Antishrink treatments

Marked improvements in wood utili-
zation will be possible if practical treat-
ments can be perfected, independent of
or supplementary to seasoning, that
will eliminate its tendency to shrink or
swell with changes in moisture condi-
tions. The results of such processing
can easily be foreseen in broader and
more secure markets for wood, espe-
cially in its finer and more exacting
uses, as in brush backs, cabinet work,
sporting equipment, shoe lasts, and the
like. Recent chemical investigations
indicate that the desired nonshrinking
quality can be secured by the formation
and deposit of synthetic resin com-
pounds within the wood substance, so
that its subeapillary structure is per-
manently bonded with a water-resistant
material.
ing with the aim of determining minimal
amounts of materials required for this
purpose, and otherwise cheapening the
treating process.

Further research is proceed-*

TIMBER MECHANICS AND
STRUCTURAL RESEARCH

SIXTY PERCENT OR MORE of the Nation’s
awed timber production is used in
building and housing. The foundation
of proper and efficient use of wood for
construction purposes is accurate knowl-
edge of its mechanical properties—its
strength in tension, bending, compres-
sion, and shear, its toughness, rigidity,
and other qualities that determine its
resistance to all kinds of stresses. In
these respects, asin others, wood was for
long the ‘unknown material.’ Vari-
able factors of species and growth were
not accurately accounted for in strength

determinations, and the rough esti-
mates and traditional practices of the
past have led to wasteful and unsatis-
factory use of untold millions of feet of
timber.

Strength tests

To supply dependable data, it was
first necessary for the Laboratory to
devise proper mechanical and statistical
methods for evaluating strength prop-
erties and then to proceed with a long
and laborious testing program. The

Data from mechanical tests of wood set standards for selection, grading,
and engineering design.

M-—31559-F

15

general result of this work, extending
over many years, has been to place wood
on a technical footing with other
modern engineering materials. Hun-
dreds of thousands of tests have
defined and differentiated the various
kinds of strength of more than 160
wood species, including all the more
important woods produced for the
Nation’s markets. Both the methods
and the results of this research have
been adopted as standard by engineer-
ing authorities in the United States and
abroad. The data provide a funda-
mental basis for design, for selection of
species for particular uses, and for find-

M-—28743-5
Modern metal connectors act as dowels or
keys in the construction of strong

timber joints.

16

ing servicable substitutes for the scarcer
and higher-priced woods. Many minor
species remain to be investigated, and
problems of the strength of second-
erowth material are assuming larger
importance with the changing character

of the American timber stand. ry

Structural investigations

On the foundation of reliable strength
values for the principal species, Labora-
tory research is able to deal effectively
with problems of wood structures and
structural parts, in which the form, size,
and condition of members must be
taken into account. Tests of full-sized
timbers have demonstrated in quantita-
tive fashion the influence of common
defects, such as knots and checks, on
strength, with the result that structural
designers have been supplied with more
efficient working-stress values, building
codes are being modernized, and timbers
are bought and sold on the basis of
strength grades, by which they can be
rationally and economically selected for
their intended loadings. The value of
the Laboratory’s contributions to struc-
tural practice is further illustrated by
the development of a special formula for
wood-column design, which has re-
placed the less accurate ones formerly
in wide use, and by the discovery of a
new engineering principle applying to
beams under shear loading, by which
large savings of material are made
through the improved design of railway-
and highway-bridge stringers and other
large members.

Joints and fastenings @

Since the joints of a structure are
usually its critical points, the strength
of the fastenings used in wood is fully
equal in engineering importance to the

A timber radio tower 326 feet high, framed with modern connectors.

strength of wood itself. Investigations
of the common timber fastenings afford
detailed data on the holding power of
nails, screws, and spikes driven in
various kinds of wood and at different
angles to the grain. Tests of bolted
joints also cover a wide range and have
removed a large factor of uncertainty
and hazard from timbered construction.
A new field of engineering construction
has been opened by the investigation
of modern plate and ring connectors
that act as dowels or keys in wood
framing. By means of these connec-
tors new types of large timber struc-
tures are coming into being throughout
the country, including long-span high-
way bridges, radio and lookout towers,
oil-field equipment, and public buildings.

Ob. cfabricated housing

The provision of easily erected, eco-
nomical, and comfortable homes for
families of small means is one of the

most urgent needs of our economic era,
and the development of more efficient
use of wood for this purpose presents a
broad responsibility for research. An
intensive study of prefabricated housing
is In progress, centering on structural
problems and extending into related
fields of investigation, such as season-
ing, moisture control, painting, and fire
resistance. A complete house of ply-
wood unit panels has been worked out
and demonstrated. Structural systems
and accessory features are being devel-
oped for house prefabrication with lum-
ber as well as sheet materials, with a
view to speed of erection, durability,
and comfort at minimum cost to the
owner.

Laminated construction

The modern era of wood construc-
tion looks forward to new forms, new
methods, and new standards of service,
while changes in the forest stand neces-

17

sitate more efficient use of material
from smaller trees. These conditions
give constantly increasing importance
to Laboratory investigations and tests
of laminated and plywood construction
in all its phases, from simple veneer
samples to built-up wall and floor sec“
tions and laminated wood arches sub-™ —
jected to loadings of thousands of
pounds. Tests are made to determine
the strength of plywood of different
combinations of species, the effect of
increasing the number of plies, of vary-
ing the ratio of core thickness to total
panel thickness, and of joining with
various kinds of glues. Possibilities of
spliced, laminated, and composite con-
struction of beams, panels, columns,
and arches built up by both nailing and
gluing are under investigation with a
MpeolbeEe view to increasing the economy of wood
Testing the strength of a glued laminated construction through the utilization of
wood arch. small pieces and material of low grades.
New types of construction embodying
these principles are demonstrated, such

Development of wood prefabricated house

ae Sica oar as the utility building of plywood
Nene e ee ln aneees supported by glued arches, now under-
a 7 going service tests on the Laboratory

grounds.

Shipping containers

An essential service performed by
wood in commerce and daily life is in
the form of containers for commodity
shipments. The work of the Labora-
tory in improving the strength and
serviceability of boxes and crates has
promoted the more efficient utilization
of billions of board feet of lumber, and
has led to savings to the consuming k
public, in freight handling charges, ~~
losses, and damage to goods, amounting
to millions of dollars a year.

It is frequently possible to redesign
a container so as to reduce the amount

of material required, to save shipping
weight and warehouse space, and at the
same time to make it stronger and safer.
The principal American wood species
have been classified for box making,
box designs have been standardized and
pecifications prepared for the proper

SMhumber, size, and spacing of nails.

Through the cooperation of railway
companies, box makers, and shippers,
the Laboratory’s findings and recom-
mendations are widely used.

Container investigations are carried
on with the aid of special equipment,
including dummy loading materials and
testing machinery which subjects pack-
ages to repeated shocks and vibrations
such as they would receive in transit.
In addition to studies of the design and
fabrication of wooden, veneered, and
composite containers and the improve-
ment of commercial specifications, the
work has been extended to the broad
field of fiberboard containers, in which
increasing quantities of wood are being
used in the form of pulp. The investi-
gation includes strength tests of the
component papers, the formation of
commercial and experimental types of

M-—22077-F
Revolving drum for testing boxes and crates.

boards, and the production and test-
ing of finished boxes, with the purpose
of bringing to this important class of
containers the engineering principles and
methods that are so largely improving
the service of wooden containers.

Equipment for corrugating and gluing fiber container board.

M-—26068—F

Woop SEASONING AND
MOISTURE CONTROL

Woop IN NATURE is a material com-
bined with one-third to two and a half
times its weight of water; a freshly cut
log 16 feet long and 18 inches in diam-
eter may have a liquid content of more
than 100 gallons.

For most uses of wood it is imperative
that the greater part of this water be
removed, a requirement that gives rise
to the complex problems of seasoning.
When wood dries, it shrinks. The
amount of shrinkage is different in
different directions in the piece, and
the result of uncontrolled drying 1s more
or less severe damage by checking,

Three of the Laboratory’s dry kilns for

20

splitting, and change of shape. Unsuc-

cessful seasoning is the cause of theg

nonuse of many wood species and tre-
mendous losses of material of other
species, and is aprolific source of difficul-
ties and dissatisfaction with wood in
service. To improve this. situation
through adequate control of seasoning
operations is a major task of scientific
research.

Air-drying

Seasoning in the open air may be
termed the natural method of wood

experimental seasoning of lumber.

M-—31266—F

drying, and under proper safeguards it
remains the most economical method
for many hardwoods and the bulk of
lower grades of softwoods. Long series
of tests have shown the common sources
of loss and damage in this field and

! eans of bringing them under control.
~ Important factors determined are prop-

er exposure of the pile with respect to
sun and wind, proper spacing of lumber
at different stages of drying, adequate
support to prevent warping and bend-
ing, and measures to prevent stain and
decay, including elevated pile founda-
tions and proper yard drainage.

Kiln-drying

The development of the lumber dry
kiln arose from the need of speeding up

the seasoning process. Very generally,
however, its use has been attended with
serious problems and variable results,
owing to the lack of precise technique.
The Laboratory’s kiln-seasoning in-
vestigations are centered on underlying
physical principles, together with the
development of apparatus and methods
to perform the drying efficiently. A
number of completely equipped experi-
mental dry kilns with accurate control
of temperature, humidity, and air cir-
culation are in constant use to test every
desired variation of conditions in the
seasoning of sample lots of lumber.
Substantial accomplishments are
shown as a result of the work thus far.
Practical methods have been developed
for seasoning the principal commercial
hardwoods and softwoods, many of

Wood samples are removed and weighed to determine moisture conditions in walls.

M-31609-F

21

which were previously considered in-
capable of being kiln-dried from the
green condition. The engineering de-
sign of dry kilns has been radically
improved. More than 5,000 commer-
cial kilns embodying principles devel-
oped at the Laboratory are in opera-
tion, and new installations so designed
by far outnumber all other types.

It is estimated that improvements
in kiln seasoning resulting from the
Laboratory’s research are already sav-
ing American wood users more than
$10,000,000 annually, and even larger
savings are possible as the findings are
more widely applied. Further investi-
gations are under way toward the adap-
tation of kiln practice to many difficult
species and to special sizes, including
precut dimension stock. Work has
begun on a broad program of research
to correlate the more severe conditions
of drying with their effects on wood
quality, with the aim of setting up
higher ranges of speed for the safe kiln
seasoning of all species.

A necessary supplement to seasoning
research is the improvement of methods

of lumber storage and handling. All
the care expended in the original drying
may be wasted because of reabsorption
of moisture by the stock while in
transit or awaiting sale. Studies of
this problem are pointing the way to
better protection of lumber at all stages.
from the mill yard to the finished™
structure. Special attention is being
given to control of moisture content of
lumber in closed sheds.

Chemical seasoning

The steeping of wood in a salt solu-
tion preliminary to drying in the kiln
or in the yard offers a new approach to
the most difficult seasoning problems.
The treatment brings about a state of
moisture equilibrium in which the wood
dries from the center outward, reversing
the usual direction, and in the final dry
condition the salts absorbed act in some
way to hold the wood against shrinkage
and change of shape. By this method
large timbers have been dried practi-
cally without checking—a result never
before attained—and wood of several

Salt treatments offer new means of seasoning the most difficult wood species.
M-—31514-F

of the most refractory species has been
seasoned rapidly and with little dam-
age. Further work is being done to
perfect the process, which holds among
its possibilities the release of millions
of feet of little-used hardwoods for
@batisfactory service.

Moisture control

By whatever means it is accom-
plished, the seasoning process has one
main purpose—to fit wood for the mois-
ture conditions it will meet in service.
Research is contributing to this end in
many ways. Instruments for the quick
determination of wood-moisture con-
tent have been developed and are now
manufactured and sold commercially.
By extensive field tests the principal
wood-moisture climates of the United
States have been charted as a guide to
seasoning for different regions. Defi-
nite moisture tolerances are thus deter-
mined for lumber according to localities
and uses and are finding an increasing
place in commercial specifications.

The modern development of air-
conditioning systems for homes and
other buildings is introducing serious
winter problems of moisture transfu-
sion, sweating, and ice formation in
walls. A thorough investigation has
been undertaken to determine the rate

M-—31513—F

Results of salt seasoning of swamp oak.

Upper group, salt seasoned; lower, speci-

mens from the same planks seasoned by
erdinary, methods.

of moisture movement in wood wall
panels of different types at various
temperatures and humidities and the
effectiveness of sheet barrier materials
in bringing it under control.

23

Woop-TREATING PROCESSES FOR
PROTECTION AND SERVICE

SURFACE or impregnation treatments of
wood to protect it or to increase its
service value in other ways are a com-
mon necessity and have been practiced,
with varying success, from the earlest
times. With the increasing volume
and diversity of wood uses in the mod-
ern era, the aid of research in examin-
ing, improving, and developing all
kinds of treating processes has become
increasingly important.

Protection against decay

Decay is by far the greatest destroyer
of wood in service. Practical methods
of preventing it mean large money sav-
ings to wood users, more lasting and
satisfactory wood structures and utili-
ties, and the curbing of a heavy drain
on forest resources. The effectiveness
and relative cost of coal-tar creosote,
zine chloride, mercury salts, and many
other preservatives in protecting wood
against decay, insects, and other de-
structive organism are studied in experi-
mental treatments and field tests of
great numbers of treated specimens,
including railway ties, piling, poles,
posts, and building timber. Research in
impregnation processes is leading the
way to better treating methods and
greater certainty of long-service life of
wood at lower cost. These studies are
of additional benefit in extending pre-
servative treatment to wood species
not before successfully treated.

Simple and inexpensive preservative
processes for fence posts and structural
timber on the farm have been devised

24

and are being further developed for use.
with various woods and new an
cheaper preservatives. Large numbers
of inquiries are received annually re-
garding the relative value of wood-
treating chemicals and methods. Au-
thoritative and impartial information
in such cases is bringing substantial
savings to thousands of wood users.

Fireproofing tests

Fireproofing investigations stand high
in potential importance. If by the

S
SS

\
= SSeS \

M—23214—-F

The effectiveness of wood-preservative ma-
terials is determined by impregnation
treatments.

addition of chemicals the combustion
of wood can be materially retarded, the
danger of spread of fire in and by
wooden structures can be largely de-
creased. Laboratory research in this
field extends over a wide range of chem-

ical treatments and types of fire-resis-
6... construction. ‘Treated wood speci-
mens are tested in specially designed
combustion apparatus. Full-sized

RE-—11208—M4

In fireproofing investigations full-sized house
parts are subjected to test in a panel furnace.

house parts are subjected to flame test
in a separate building equipped with a
panel furnace having 67 large gas
burners. Although highly effective fire-
proofing treatments are now available,
they are too expensive for general con-
struction purposes. The objective of
research is to reduce costs and to bring

the benefits of fire-retardant wood

within reach of the average home
builder.

Painting and

moisture-proofing

The Laboratory is making definite
contributions toward more lasting and
satisfactory service of paints and other
coatings used on wood. The relative
efficiency of large numbers of moisture
retardants and varnishes has been deter-
mined. Exposure tests of painted
panels in many locations have demon-
strated the relative paint-holding power
of the principal commercial wood
species. Useful discoveries have been
made in methods of applying paint to
wood and the choice of priming mate-
rials.

Examination of numerous failures in
the repainting of houses shows, how-
ever, that the life of a coating cannot be
wholly predicted from the immediate
conditions of appheation, but that the
service given depends on a proper or
improper combination of the new paint
with coats that have preceded it.
his tact, pots to the jmeeds of- a
thoroughgoing classification of house
paints according to the long-time
maintenance programs of home owners.
The work of classification, recently
begun, involves a wide range of chem1-
eal research and service tests. The
findings already indicate that by a
proper distinction of paint types the

25

complexity of present paint markets
may be greatly simplified, with result-
ing benefits to the user in lower costs
and better service.

Gluing

Gluing is a process as old as the wood
working art, and in the era of composite
and laminated construction that is now
beginning its importance is destined to
increase. Many problems of wood
gluing have been solved by Laboratory
research. Effects of the many varia-
bles involved in gluing—temperature,
glue consistency, kind of wood, kind of
glue, thickness of spread, time of

M-—29826—

TI

Protective efficiency of paints on wood is
studied by exposure of panels.

“ NESS
DCFKR RQ
SN S
~ SK

XG
“Settee

26

spreading, time in press—have been
isolated and evaluated, and the result
is that by proper observance of these
factors all commercial woods can today
be glued with animal, vegetable, blood,
or casein glue in joints that are stronger
than the wood itself. Woodworking
@raustries are applying the findings of
research, with corresponding benefit
to users, in better products, more eco-
nomical service, and reduced waste of
wood.

Problems of far-reaching importance
that remain for investigation pertain
to the permanent water resistance of
elue joints and to fundamental improve-
ments in the nature of adhesives.
Glues that contain no water are being
developed. The active aid of research
is needed to make them cheaper, better,
and more generally adaptable.

Veneer and plywood

Plywood is sheet material made by
gluing together thicknesses of veneer
with the grain of successive layers at
right angles. Present-day utilization
trends point to increasing importance
of plywood in construction and fabri-
cation. Factors in its favor are its
strength, the uniformity of its prop-
erties, and the large lightweight units
in which it can be produced. There is
need for a more exact determination of
the properties of plywood as they are
affected by the kind, quality, and

e

M—30142—-F

Mechanical spreading of glue.

_dimensions of veneer, the number of

plies, gluing and pressing technique,
and other manufacturing variables.
A comprehensive investigation of these
problems is under way. The sheet
material is obtained from the log in the
Laboratory’s veneer-cutting plant. The
veneer is glued up into plywoods of
various types and thicknesses, which are
tested singly and in structural combina-
tions. The tests include determina-
tions of strength, resistance to weather-
ing, and moisture and heat diffusion,
as well as the effectiveness of different
glues and gluing methods used in mak-
ing the plywood.

27

Woop PATHOLOGY

INVESTIGATIONS OF DEFECTS in wood
and wood products caused by fungus
infection are conducted at the Labora-
tory by the Division of Forest Path-
ology, Bureau of Plant Industry, United
States Department of Agriculture, in
correlation with other Laboratory
activities.

Wood-destroying fungi

The effects of wood-destroying fungi
upon the structure and service life of
wood are examined, and temperature
and moisture conditions favorable and
unfavorable to fungus growth are de-
termined. The causes of decay in
buildings and wood products are in-
vestigated. Rules of construction for
the avoidance of decay have been de-
veloped, with consequent large savings
to thousands of home owners.

Toxicity of preservatives

The toxicity or fungicide value of
wood-preservative chemicals is deter-
mined by their effects on typical wood-
destroying and staining fungi grown

A blue-stain fungus in wood (magnified).

M-—15156—-F

in pure cultures. The adaptation of
various chemicals to mechanical or
hand-dipping treatments of freshly

sawed lumber is a phase of the study j

having wide commercial application in
the prevention of sap stain during air
seasoning.

Yard sanitation

Heavy losses to users occur as a
result of the storage of wood under
improper conditions of drainage, ven-
tilation, and exposure. Studies and
recommendations are made, in coopera-
tion with other divisions of the Lab-
oratory, for improving storage of gen-
eral lumber stocks at sawmills and
retail yards and for the better storage
of pulpwood and pulp, box lumber,
veneers, staves, vehicle parts, and
other wood products.

2184—M

A decay fungus in wood (magnified).

PuLp AND PAPER

THe puRPOSE of the Laboratory’s
pulp and paper investigations is_ to

increase possibilities of economical pro-
oe... higher yield, and better pulp
quality from our native woods, in-
cluding those now little used or unused.
Millions of tons of pulp and paper are
imported annually into the United
States from abroad to supplement
waning supplies of eastern spruce,
balsam fir, and hemlock, which have
heretofore been the mainstay of the
domestic industry; meanwhile, other
American woods are being wastefully
used or neglected which, if adapted to
pulping purposes, could supply our
present paper requirements several
times over. Alteration of these con-
ditions would mean better returns to
forest management through the utiliza-
tion of small trees and_ thinnings,
profitable yields from lands now idle,
and employment and wages for thou-
sands of workers.

The need of a broad and dependable
domestic basis of pulp supply seems
destined to become more and more
urgent as time goes on. The utiliza-
tion of pulp products in the United
States reached 13 million tons in 1929.
Despite a temporary recession it is
again on the increase, with a prospective
annual consumption of 25 million tons
within this century. The develop-
ment of new paper commodities and
pulp conversion products such as rayon
ae cellopahne is mounting in volume

and variety. Meanwhile, world con-
sumption of pulp is also increasing
with changing habits and standards
of literacy in many countries abroad,
and it is entirely possible that, as

American requirements approach a
maximum, cheap and abundant pulp
imports such as we enjoy at present
may no longer be forthcoming.

These considerations emphasize the
importance of better and more adequate
utilization of our own pulpwood re-
sources. Toward its accomplishment
the Laboratory has mobilized a varied
research attack.

Additional species
for pulping

By systematic pulping tests the
Laboratory determines basic data for

M—22506—F
Wood is reduced to pulping size by use of a
mechanical chipper.

29

American woods as regards their adap-
tability to standard pulp-manufactur-
ing processes, their yields, chemical
consumption, bleaching characteristics,
and other factors of production. Ap-
plying and amplifying the results,
present studies are centered on the
development of useful pulps from
important species and regional groups.
In the Northeastern and Lake States
the stands of second-growth hard-
woods—maple, birch, beech, and aspen
—that have sprung up in the wake of
logging offer possibilities as a sup-
plementary source of pulpwood. Ex-
periments with these woods are being

M-26174-F

Pulping experiments over a wide range of

chemical concentrations and pressures are

made possible by use of a chrome-nickel
lined digester.

30

carried forward. It has been shown
that in the grinding of hardwoods a
proper dressing of the stone surface
will pulp the wood with minimum
destruction of fiber length, and also
that if the high pentosan content of
these species is retained in chemical
pulps, much stronger papers can b
produced from them than had been
thought possible. Studies of aspen
pulping have been especially helpful
in increasing paper production from a
prolific species that at present has few
uses.

The Laboratory has devoted special
attention to the production of news-
print from southern woods. Because
of the large tonnage of newsprint
consumed by the United States and
the fact that much of this is imported
from abroad, the possibilities of devel-
oping a domestic source of supply,
particularly from the plentiful southern
species, has commanded increasing
interest. However, certain disadvan-
tages such as poor color and high resin
content in the pines, particularly the
older stands, in contrast with the
eminently suitable properties and cheap-
ness of northern spruce have retarded
any realistic development of a news-
print industry in the South, although
experimental sulphite and ground-wood
pulps of newsprint grade were produced
at the Laboratory more than 20 years
ago.

Increasing costliness of spruce and
balsam, combined with the fact that
the young second-growth pine is fairly
free from heartwood and relatively low
in resin, has tended to renew research
efforts in newsprint production and
experiments at the Laboratory and
elsewhere. By selecting young pine
trees of limited heartwood and resin
content, newsprint-grade papers have

?

been produced on a laboratory and
semicommercial basis from combina-
tions of sulphite and ground-wood
pulps, such as are normally used by
the industry in manufacturing this
type of paper.

Since production of newsprint by
his method requires specially selected
wood, which is an added cost and leaves
much heart-bearing cull wood to be
disposed of, the Laboratory has devel-
oped the use of semibleached sulphate
pulp as a substitute for the sulphite,
and has proved the effectiveness of this
procedure by extended tests. The
alkaline sulphate process readily re-
duces heartwood, does not require
light-colored wood, and practically elim-
inates the possibility of pitch diffi-
culties. The currently proposed news-
print developments in the South are in
practically all cases tending toward this
latter method of conversion.

The Laboratory has not only pro-
duced newsprint from various com-
binations of pine but has also used
mixtures of pine with such southern
hardwoods as gum. These develop-
ments offer possibilities for use of the
southern hardwoods and for minimizing
pitch troubles should these arise in
mill operations.

In the forests of the Pacific North-
west, the Nation has other great
supplies of actual and potential pulp-
woods. Enough Douglas fir is left on
the ground as logging waste each year
to duplicate almost our entire pulp
output from domestic sources—if
Douglas fir can be adapted to diversi-

ed pulp production. The Laboratory
is working to secure this result by
special modifications of the sulphate
and other processes. Experimental
papers of good quality and strength
have been obtained. Pulping experi-

M-—26380-F
On the way to the paper machine the pulp,
after bleaching, is further refined
in the beater.

ments also with western larch, white
fir, red cedar, Sitka spruce, and other
western species are returning a promis-
ing variety of book, writing, wrapping,
and newsprint papers.

Improvement of
pulping processes

As urgently needed as the extension
of pulping to new species is the pro-
eressive improvement of pulping opera-
tions, looking to the more efficient
utilization of woods of all species.
Studies of chemical pulping are carried
on constantly and are showing the way
to substantial increases of yields and
improvement of pulp quality. Appli-
cation of the findings is resulting in
more satisfactory and economical pro-
duction through a proper balance of

31

the factors of time, temperature, and
concentration of chemicals in cooking.
Research in wood grinding is likewise
establishing useful principles of control
which are having a wide effect in im-
proved quality of pulp and lower power
consumption; an extended program o
grinding studies is in progress with m
and complete equipment.

A special contribution of the Labora-
tory to the procurement of high yields
from the standard and less-used pulping
species is the development of the so-
called semichemical processes. Where-
as the usual chemical methods return
only 40 to 50 percent of the wood as
useful fiber, the new processes return
from 55 to 80 percent. In one of them
neutral chemicals are used, in another
acid sulphite liquors, and in a third al-
kaline reagents. In each process the
pulping of the partially cooked wood is
completed in a rod mill or other disin-
tegrating device. An interesting appli-
cation is the conversion of extracted
chestnut chips into container board,
now proceeding commercially on a large
scale.

The use of a soda or ammonia base
for sulphite pulping offers a distinct
advantage over the use of the customary
lime base, in that the liquors can be
effectively applied in cooking not only
the common pulpwood species but also
the more resinous woods not now reduci-
ble by the sulphite process. The Labor-
atory is advancing the technique of the
new method, by means of which much
additional raw material for white papers
may be made available to both north-
ern and southern mills. Yurthomo@

M—26040—F

The tensile test—one cf many tests used in
evaluating paper quality.

M—26399-F

An experimental Fourdrinier machine, with
press and drier rolls and calender, trans-
forms the pulp into finished paper. Oper-
ating elements are under precise control.

N

definite progress is being made in the
development of a recovery system to
return the used chemicals cheaply. This
step is necessary to the general adopt-
tion of the new bases. Its successful
accomplishment will be of immense pub-
r benefit by making possible the elimi-

nation of sulphite waste-liquor dis-
charges, which at present are a major
source of stream pollution.

Pulp refinement
and paper making

The utility of a given wood species
for paper production is not determined
by its pulping behavior alone but by

the possibilities of adapting the pulp
to the varied requirements of paper
making. Laboratory research is there-
fore intimately concerned with all the
other manipulations involved—bleach-
ing, beating, refining, paper-machine
operations, and finally the testing of the
finished product and the salvaging of
waste fiber and chemicals. Many tasks
lie ahead, as for instance the correla-
tion of fiber properties with intensity
of beating, the improvement of multi-
stage bleaching processes, and the analy-
sis of some 30 machine variables in
relation to the strength, finish, inking
quality, glare, and moisture resistance
of the finished paper.

How TO USE THE LABORATORY

ALL THE INFORMATION that the Forest
Products Laboratory has gained through
years of research is available to the
public. Every year thousands of in-
quiries are answered by letter and
problems are discussed with those who
come to the Laboratory seeking advice
on problems of wood utilization.

In cases where the problem presented
is of such scope and difficulty as to
warrant a cooperative research project,
the work will be undertaken if consistent
with the Laboratory’s public objectives
and subject to advance agreement as to

ethods and payment of costs. The
Laboratory’s guiding purpose in such

studies is to secure facts that will pro-
mote the best use of wood. A pamphlet
explaining the cooperative service more
fully is obtainable on request.

Laboratory publications are available
covering the main findings of its re-
search work, and classified mailing lists
are maintained for the distribution of
current information in different fields
of wood use. General visitors are con-
ducted through the Laboratory at
regular hours.

Inquiries should be addressed to the
Director, Forest Products Laboratory,
Madison, Wis.

WISE TIMBER USE IS THE
BEST TIMBER CONSERVATOR

51718°—38

33