OPERATIONS FOLLOWING DYEING.
WASHING, SOAPING, DRYING.
After loose cotton or wool, or cotton and woollen yarns, or piece goods
of every description have been dyed, before they can be sent out for
sale they have to pass through various operations of a purifying
character. There are some operations through which cloths pass that have
as their object the imparting of a certain appearance and texture to
them, generally known as finishing processes; of these it is not
intended here to speak, but only of those which precede these, but
follow on the dyeing operations.
These processes are usually of a very simple character, and common to
most colours which are dyed, and here will be noticed the appliances and
manipulation necessary in the carrying out of these operations.
=Squeezing or Wringing.=--It is advisable when the goods are taken out
of the dye-bath to squeeze or wring them according to circumstances, in
order to press out all surplus dye-liquor, which can be returned to the
dye-bath if needful to be used again. This is an economical proceeding
in many cases, especially in working with many of the old tannin
materials like sumac, divi-divi, myrobolams, and the modern direct dyes
which in the dyeing operations are not completely extracted out of the
bath, or in other words, the dye-bath is not exhausted of colouring
matter, and, therefore, it can be used again for another lot of goods,
simply by adding fresh material to make up for that absorbed by the
first lot of goods.
Loose wool and loose cotton are somewhat difficult to deal with by
squeezing or wringing, but the material may be passed through a pair of
squeezing rollers, such as are shown in Fig. 31, which will be more
fully dealt with later on. The machine shown is made by Messrs Read
Holliday & Sons.
[Illustration: FIG. 31.--Squeezing Rollers.]
_Yarns in Hanks._--In the hank-dyeing process the hanks are wrung by
placing one end of the hank on a wringing horse placed over the
dye-tub, a dye stick on the other end of the hank giving two or three
sharp pulls to straighten out the yarn, and then twisting the stick
round, the twisting of the yarns puts some pressure on the fibres,
thoroughly and uniformly squeezing out the surplus liquor from the yarn.
_Hank-wringing Machines._--Several forms of hank-wringing machines have
been devised. One machine consists of a pair of discs fitted on an axle;
these discs carry strong hooks on which the hanks are placed. The
operator places a hank on a pair of the hooks. The discs revolve and
carry round the hank, during the revolution the hank is twisted and the
surplus liquor wrung out, when the revolution of the discs carries the
hank to the spot where it entered the machine the hooks fly back to
their original position, the hank unwinds, it is then removed and a new
hank put in its place, and so the machine works on, hanks being put on
and off as required. The capacity of such a machine is great, and the
efficiency of its working good.
Mr. S. Spencer of Whitefield makes a hank-wringing machine which
consists of a pair of hooks placed over a vat. One of the hooks is
fixed, the other is made to rotate. A hank hung between the hooks is
naturally twisted, and all the surplus liquor wrung out. The liquor
falling into the vat.
_Roller Squeezing Machines for Yarn._--Hanks may be passed through a
pair of indiarubber squeezing rollers, which may be so arranged that
they can be fixed as required on the dye-bath. Such a pair of rollers is
a familiar article, and quite common and in general use in dye houses.
_Piece Goods._--These are generally passed open through a pair of
squeezing rollers which are often attached to the dye-vat in which the
pieces are dyed.
_Read Holliday's Squeezing Machine._--In Fig. 31 is shown a squeezing
machine very largely employed for squeezing all kinds of piece goods
and cotton warps after dyeing or washing. It consists of a pair of heavy
rollers on which, by means of the screws shown at the top, a very
considerable pressure can be brought to bear. The piece is run through
the eye shown on the left, by which it is made into a rope form, then
over the guiding rollers and between the squeezing rollers, and into
waggons for conveyance to other machines. This machine is effective.
Another plan on which roller, or rather in this case disc, squeezing
machines is made, is to make the bottom roller with a square groove in
the centre, into this fits a disc, the cloth passing between them. The
top disc can by suitable screws be made to press upon the cloth in the
groove, and thus squeeze the water out of it.
=Washing.=--One of the most important operations following that of
dyeing is the washing with water to free the goods, whether cotton or
woollen, from all traces of loose dye, acids, mordanting materials,
etc., which it is not desirable should be left in, as they might
interfere with the subsequent finishing operations. For this purpose a
plentiful supply of good clean water is required; this should be as soft
as possible, free from any suspended matter which might settle upon the
dyed goods, and stain or speck them.
Washing may be done by hand, as it frequently was in olden days, by
simply immersing the dyed fabrics in a tub of water, shaking, then
wringing out, again placing in fresh water to finish off. Or if the
dye-works were on the banks of a running stream of clean water the dyed
goods were simply hung in the stream to be washed in a very effectual
manner.
In these days it is best to resort to washing machines adapted to deal
with the various kinds of fibrous materials and fabrics in which they
can be subjected to a current of water.
[Illustration: FIG. 32.--Yarn-washing Machine.]
_Loose Wool and Cotton._--If this has been dyed by hand then the washing
may also be done in the same way by hand in a plain vat. If the dyeing
has been done on a machine, then the washing can be done on the same
machine.
_Yarns._--Yarn in the cop form is best washed in the machine in which it
is dyed.
_Yarns in Hanks._--A very common form of washing machine is shown in
Fig. 32. As will be seen it consists of a wooden vat, over which are
arranged a series of revolving reels on which the hanks are hung. The
hanks are kept in motion through the water, and so every part of the
yarn is thoroughly washed. Guides keep the hanks of yarn separate and
prevent any entanglement one with another. A pipe delivers constantly a
current of clean water, while another pipe carries away the used water.
Motion is given to the reels in this case by a donkey engine attached to
the machine, but it may also be driven by a belt from the main driving
shaft of the works. This machine is very effective.
[Illustration: FIG. 33.--Dye-house Washing Machine.]
_Piece Goods._--Piece goods are mostly washed in machines, of which two
broad types may be recognised; first, those where the pieces are dealt
with in the form of ropes in a twisted form, and, second, those where
the pieces are washed open. There are some machines in which the cloths
may be treated either in the open or rope form as may be thought most
desirable.
[Illustration: FIG. 34.--Cloth-washing Machine.]
Fig. 33 represents a fairly well-known machine, made by Messrs. Mather &
Platt, in which the pieces are treated in a rope-like form. It consists
of a trough in which a constant current of water is maintained. At one
end of this trough is a square beating roller, at the other a wooden
lattice roller. Above the square beater, and out of the trough, are a
pair of rollers whose purpose is to draw the cloth through the machine
and also partly to act as squeezing rollers. As will be seen the cloth
is threaded in rope form spirally round the rollers, passing in at one
end and out at the other, pegs in a guide rail serving to keep the
various portions separate. The square beater in its revolutions has a
beating action on the cloth tending to more effectual washing. The
lattice roller is simply a guide roller.
Fig. 34 shows a washing machine very largely used in the wool-dyeing
trade. The principal portion of this machine is of wood.
The internal parts consist of a large wooden bowl, or oftener, as in the
machine under notice, of a pair of wooden bowls which are pressed
together by springs with some small degree of force. Between these bowls
the cloth is placed, more or less loosely twisted up in a rope form, and
the machines are made to take four, six or eight pieces, or lengths of
pieces, at one time, the ends of the pieces being stitched together. A
pipe running along the front of the machine conveys a constant current
of clean water which is caused to impinge in the form of jets on the
pieces of cloth as they run through the machine, while an overflow
carries away the used water. The goods are run in this machine until
they are considered to be sufficiently washed, which may take half to
one and a half hours.
In Fig. 35 is shown a machine designed to wash pieces in the broad or
open state. The machine contains a large number of guide rollers, built
more or less open, round which the pieces are guided--the ends of the
pieces being stitched together. Pipes carrying water are so arranged
that jets of clean water impinge on and thoroughly wash the cloth as it
passes through--the construction of the guide rollers facilitating the
efficient washing of the goods.
[Illustration: FIG. 35.--Cloth-washing Machine.]
=Soaping.=--- Sometimes yarns or cloths have to be passed through a soap
bath after being dyed in order to brighten up the colours or develop
them in some way. In the case of yarns this can be done on the reel
washing machine such as is shown in Fig. 32. In the case of piece goods,
a continuous machine, in which the washing, soaping, etc., can be
carried on simultaneously, is often employed. Such a machine is shown in
Fig. 36. It consists of a number of compartments fitted with guide
rollers so that the cloth passes up and down several times through the
liquors in the compartments. Between one compartment and another is
placed a pair of squeezing rollers. The cloth is threaded in a
continuous manner, well shown in the drawing, through the machine. In
one compartment it is treated with water, in another soap liquor, in
another water, and so on; and these machines may be made with two, three
or more compartments as may be necessary for the particular work in
hand. As seen in the drawing, the cloth passes in at one end and out at
the other finished. It is usually arranged that a continuous current of
the various liquors used flows through the various compartments, thus
ensuring the most perfect treatment of the cloths.
[Illustration: FIG. 36.--Washing and Soaping Vats.]
=Steaming.=--Sometimes it becomes necessary to subject dyed goods to a
process of steaming, as, for instance, with steam aniline blacks, khaki
shades, alizarine reds, etc., for the purpose of more fully developing
and fixing the dye upon the fibre. In the case of yarns, this operation
is carried out in the steaming cottage, one form of which is shown in
Fig. 37. It consists of a horizontal cylindrical iron vessel like a
steam boiler, one end is entirely closed, while the other is made to
open and be closed tightly and hermetically. The cottage is fitted with
the necessary steam inlet and outlet pipes, drain pipes for condensed
water, pressure gauges. The yarn to be steamed is hung on rods placed on
a skeleton frame waggon on wheels which can be run in and out of the
steaming cottage as is required. The drawing shows well the various
important parts of the machine. In the case of piece goods these also
can be hung from rods in folds on such a waggon, but it is much more
customary to employ a continuous steaming chamber, very similar to the
ageing and oxidising machine shown in Fig. 38, and also used in the
dyeing of aniline black.
[Illustration: FIG. 37.--Steaming Cottage.]
[Illustration: FIG. 38.--Steaming and Ageing Chamber.]
=Drying.=--Following on the washing comes the final operation of the
dyeing process, that of drying the dyed and washed goods. Textile
fabrics of all kinds after they have passed through dye-baths, washing
machines, etc., contain a large amount of water, often exceeding in
weight that of the fibre itself, and to take the goods direct from the
preceding operations to the drying plant means that a considerable
amount of fuel must be expended to drive off this large amount of water.
It is therefore very desirable that the goods be freed from as much of
this water as possible before they are sent into any drying chambers,
and this may be done in three ways, by wringing, squeezing and
hydro-extracting. The first two methods have already been described (p.
239, etc.) and need not again be alluded to; the last needs some
account.
[Illustration: FIG. 39.--Hydro-extractor.]
Hydro-extractors are a most efficient means for extracting water out of
textile fabrics. They are made in a variety of forms by several makers.
Essentially they consist of a cylindrical vessel, or basket, as it is
called, with perforated sides so constructed that it can be revolved at
a high speed. This vessel is enclosed in an outer cage. The goods are
placed in the basket, as it is termed, and then this is caused to
revolve at high speed, when centrifugal action comes into play, and the
water contained in the goods finds its way to the outside of the basket
through the perforations, and so away from the goods. Hydro-extractors
are made in a variety of sizes and forms--in some the driving gear is
above, in others below the basket; in some the driving is done by
belt-gearing, in others a steam engine is directly connected with the
basket. Figs. 39 and 40 show two forms which are much in use in the
textile industry. They are very efficient, and extract water from
textile goods more completely than any other means, as will be obvious
from a study of the table below.
[Illustration: FIG. 40.--Hydro-extractor.]
The relative efficiency of the three systems of extracting the moisture
out of textile fabrics has been investigated by Grothe, who gives in his
_Appretur der Gewebe_, published in 1882, the following table showing
the percentage amount of water removed in fifteen minutes:--
Yarns. Wool. Silk. Cotton. Linen.
Wringing 44.5 45.4 45.3 50.3
Squeezing 60.0 71.4 60.0 73.6
Hydro-extracting 83.5 77.0 81.2 82.8
Pieces.
Wringing 33.4 44.5 44.5 54.6
Squeezing 64.0 69.7 72.2 83.0
Hydro-extracting 77.8 75.5 82.3 86.0
In the practical working of hydro-extractors it is of the utmost
importance that the goods be carefully and regularly laid in the
basket--not too much in one part and too little in another. Any
unevenness in this respect at the speed at which they are driven lays
such a strain on the bearings as to seriously endanger the safety of the
machine.
After being wrung, squeezed or hydro-extracted the goods are ready to be
dried. In the case of yarns, this may be done in rooms heated by steam
pipes placed on the floor, the hanks being hung on rods suspended from
racks arranged for the purpose.
[Illustration: FIG. 41.--Automatic Yarn-dryer.]
Where large quantities of yarn have to be dried, it is most economical
to employ a yarn-drying machine, and one form of such is shown in Fig.
41. The appearance of the machine is that of one long room from the
outside; internally it is divided into compartments, each of which is
heated up by suitably arranged steam pipes, but the degree of heating in
each compartment varies--at the entrance end it is high, at the exit end
lower. The yarn is fed in at one end, being hung on rods, and by
suitable gearing it is carried directly through the various chambers or
sections, and in its passage the heat to which it is subjected drives
off the water it contains. The yarn requires no attention from the time
it passes in wet at the one end of the machine and comes out dry at the
other end. The amount of labour required is slight, only that
represented by filling the sticks with wet yarn and emptying them of the
dried yarn. The machine works regularly and well.
[Illustration: FIG. 42.--Truck Yarn-dryer.]
The drying is accomplished by circulating heated air through the yarns,
this heating being effected by steam coils, fresh air continually enters
the chambers, while water-saturated air is as continually being taken
out at the top of the chamber. One of the great secrets in all drying
operations is to have a constant current of fresh hot air playing on the
goods to be dried; this absorbs the moisture they contain, and the
water-charged air thus produced must be taken away as quickly as
possible.
[Illustration: FIG 43.--Drying Cylinders.]
Fig. 42 shows what is called a truck yarn-dryer, which consists of a
chamber heated with steam pipes and fitted with an exhausting fan to
draw out the air and water vapour which is produced. The yarns are hung
on trucks which can be run in and out of the chamber for filling and
emptying.
_Piece Goods._--The most convenient manner of drying piece goods is to
employ the steam cylinder drying machine, such as is shown in Fig. 43.
This consists of a number of hollow tin or copper cylinders which can be
heated by steam passing in through the axles of the cylinders, which are
made hollow on purpose. The cloth to be dried passes round these
cylinders, which revolve while the cloth passes. They work very
effectually. The cylinders are arranged sometimes, as in the drawing,
vertically; at other times horizontally.