24 MODERN PAPER-MAKING
cloth. This action loosens extraneous matter such as dust and dirt, and most
of it falls through the meshes of the wire cloth on to the floor below, from
which it is cleaned out at convenient intervals, of it may be sucked out by a
fan and blown into water.
The whole duster is enclosed in a dust-proof wooden box, the front side of
which may be removed for cleaning purposes. The cone is supported on four
wheels, on which it rides, with a steel band or tyre fixed to each end of the
cone to coincide with the wheels. In addition, there is a toothed wheel bolted
to the cone at one end, and this engages with a small pinion which transmits
the drive from the motor or shaft pulley.
The rags are fed in at the small end, and travel slowly down towards the
large end, from which they are discharged into suitable receptacles or on to a
travelling band.
After the rags have passed through the duster they may be again overlooked
by women, to remove buttons and other contraries which may have been
missed. This is best accomplished by having a travelling band about 3 feet
in width to carry the rags along after they leave the duster. The women stand
on either side of the band and examine the rags as they pass.
RAG BOILING
It is necessary now to boil the rags with water under pressure, and in most
cases to assist the reducing action by means of caustic soda, soda ash or lime,
or sometimes by a combination of two of those chemicals.
The boiling is usually carried out in spherical or cylindrical revolving
boilers (Fig. 5), and in our opinion the best form, is the spherical type, on
account of the ease with which it may be filled and emptied. While a spherical
boiler may be filled by one man, and almost empties itself, a cylindrical boiler,
even if it has two manholes, nearly always needs to be packed, and this necessi-
tates the men entering it, and it also takes much more time and labour to
empty.
The boiler is first filled with the required amount of water, and the rags are
then put in. When the charge is complete the caustic soda liquor or soda ash
is added, the lid bolted on and the steam turned on.
The caustic soda to be used should be broken up and weighed, and then
dissolved in hot water, or a supply of the solution may be kept at the proper
density, and a known number of gallons can then be run into the boiler.
It is necessary that great care should be taken to ascertain the exact amount
" of caustic soda which is being used for each boil, as otherwise endless trouble
will arise through too much or too little being used and the boil being spoilt.