THE DYEING OF COTTON
The dyeing of cotton is difficult with the natural dye stuffs, there
are only a few colours which can be said to be satisfactory. The
fastest known in earlier days was Turkey red, a long and difficult
process with madder and not very practical for the small dyer. It had
its origin in India where it is still used; red Indian cotton is one
of the fastest colours known. Catechu is another excellent cotton dye
used for various shades of brown, grey and black. A cold indigo vat is
used for blue, Indigo Extract is not used. Yellows can be got with
weld, flavin, turmeric (for which cotton has a strong attraction), and
fustic. Great care is to be taken in dyeing yellow as it is not very
fast to light. Greens may be got by dyeing in the indigo vat and then
with a yellow recipe, purples from logwood with tin mordant, but
purples and greens are unsatisfactory, and not suitable to the
vegetable dyer.
BOILING OUT
Before dyeing cotton in the raw state, or in yarn spun direct from the
raw state, it must be boiled for several hours to extract its natural
impurities. For dark colours water alone may be used, but for light
and bright colours a weak solution of carbonate of soda, 5%; or of
caustic soda, 2%, should be used.
MORDANTS
_Alum._ Alum (1/4 weight of cotton) is dissolved in hot water with
carbonate of soda crystals, or other alkali (1/4 weight of alum); work
cotton in the solution, steep for several hours or overnight. Then
well wash. Aluminium acetate solution as for silk (page 56) may be
used. After drying, the cotton may be passed through a fixing solution
of some alkali, for examples see page 50. Before mordanting with
alum, the cotton is often prepared with tannic acid.
_Iron._ Iron is usually employed as a "saddening" agent, i.e. the
cotton after dyeing is steeped in a cold solution of the mordant. A
further use is in dyeing black, when the cotton, after being prepared
with tannin, is steeped in a cold solution of Iron. This process by
itself gives a dark colour before any dye is used.
_Tin._ Tin is rarely used alone as a mordant for cotton but brightens
the colour in combination with other mordants.
_Chrome._ Chrome is used for browns and other colours with Catechu.
After boiling in a solution of the dye stuff, boil a short time in
chrome solution, this oxidizes the colouring matter of the Catechu.
_Copper._ Copper is sometimes added in small quantities to the dye
bath for brown or yellow to vary the shade.
_Tannin (Tannic acid)._ Cotton and linen strongly attract tannin and
when prepared with it they are able to retain dyes permanently. Cotton
saturated with tannin attracts the dye stuff more rapidly, and holds
it. Tannic acid is the best tannin for mordanting as it is the purest
and is free from any other colouring matter; it is, therefore, used
for pale and bright shades. But for dark shades, substances containing
tannic acid are used, such as _sumach_, _myrobalans_, _valonia_,
_divi-divi_, _oak galls_, _chestnut_ (8 to 10 per cent tannin),
_catechu_.
Cotton and linen are prepared with tannin after they have been through
the required cleansing, and, if necessary, bleaching operations. A
bath is prepared with 2 to 5 per cent of tannic acid of the weight of
the cotton, and a sufficient quantity of water. For dark shades, 5 to
10 per cent should be used. The bath is used either hot or cold. It
should not be above 60 deg.C. The cotton is worked in this for some
time, and then left to soak for 3 to 12 hours, while the bath cools.
It is then wrung out and slightly washed.
The following gives the relative proportions of the various substances
containing tannin:--1 lb. tannic acid _equals_ 4 lbs. sumach, 18 lbs.
myrobalans, 14 lbs. divi-divi, 11 lbs. oak galls.
_Examples from various recipes_:
For 10 lbs. cotton use 12 ozs. tannic acid.
" 50 " " " 10 lbs. sumach.
" 40 " " " 10 lbs. "
" 20 " " " 2 lbs. yellow (or black) catechu.
" 20 " " " 3 lbs. catechu with 3 ozs. blue vitriol.
Some recipes soak the cotton 24 hours, others 48.
RECIPES FOR DYEING
(1) INDIGO VAT
Take 3 oz. well ground indigo, mix into a paste with hot water. Slake
3 oz. Quicklime and boil with 6 oz. Potash or Soda ash in sufficient
water, let it settle, pour off the clear liquor in which dissolve the
indigo paste, boil or keep hot 24 hours; it should then have the
consistency of thick cream, with much froth. During the boiling, slake
another 3 oz. quicklime, boil in a pint of water for 15 minutes, let
settle, pour off the clear liquor in which dissolve 4 to 5 oz. green
copperas. Add the indigo and copperas solutions to 5 gallons water,
stir well, let vat rest, stir once or twice during 24 hours or until
it appear ready for dyeing. Before use it should be stirred and let
stand 2 hours. It should be a clear yellowish green with much scum.
The cotton to be dyed should be entered in dips of increasing lengths
of time, as 1, 5, 10, 20 minutes, and aired in between, according to
depth of shade required. It should then be well washed, passing
through water slightly acidulated with Sulphuric acid (a teaspoonful
to 1 gallon). When this vat appears exhausted and turns a dark colour
it may be revived by adding 2 or 3 oz. Green Copperas dissolved as
before. When again exhausted, more of all the ingredients must be
added.
(2) LIME COPPERAS VAT
2 oz. Indigo, 4 oz. Copperas, 5 oz. Quicklime (fresh). Mix Indigo into
a paste with hot water. Dissolve copperas in hot water. Slake lime.
Fill earthenware jar with about 5 gallons cold water and add the
Indigo, copperas and slaked lime in that order. Stir well, cover and
let stand till next day or until vat is in proper condition; it should
be clear brownish yellow with possible blue scum. There will be some
sediment. The dyeing process is as in (1).
(3) RED
(For 1 lb. cotton.) The Turkey Red process is long and difficult. (1)
Boil yarn 6 to 8 hours in a solution of carbonate of soda, 1-1/2 oz.,
wash well and dry. (2) Prepare a solution of 2 fluid ozs. Turkey Red
oil, 2 ozs. carbonate of soda at 100 deg.F., work cotton in this till
thoroughly saturated, wring out, dry. (3) Repeat No. 2. (4) Repeat No.
2. (5) Steep 3 or 4 hours in solution of 1 oz. carbonate of soda at
100 deg.F., wring out, dry. (6) Repeat No. 5 with a slight increase of
soda. (7) as No. 6. (8) Steep 10 hours in water at 100 deg.F., dry. The
cotton should now be clear white. (9) Steep 4 hours in solution of
1-1/2 oz. tannic acid or 4 oz. Galls, at 100 deg.F., wring out, dry.
(10) Steep 24 hours in solution made by dissolving 10 oz. alum in hot
water, and slowly adding 2-1/2 oz. carbonate of soda crystals, wring
out and dry. The cotton is now grey coloured. (11) Dye with 2 lbs.
madder. Bring slowly to the boil, boil for 1 hour, a white scum on the
surface denotes the cotton has absorbed all its colour. A teaspoonful
of chalk may be added to the dye-bath. The cotton is now dark claret
colour. (12) To brighten, boil 3 or 4 hours in a solution of 1/2 oz.
carbonate of soda crystals and 1/2 oz. soap. The bath should be
covered, except for a small outlet for the steam which otherwise
should be retained as much as possible. (13) The cotton can be further
brightened by boiling with 1/2 oz. soap and a teaspoonful of Tin. Wash
and dry.
(4) RED
(For 1 lb.) After boiling out in soda, wash and dry. Steep overnight
in a hot bath of 1-1/2 oz. Tannic acid or 4 oz. Galls, dry, steep in
cold solution of 1/4 lb. alum and 1/2 oz. chalk, dry, add 2 oz. more
alum to solution and steep as before, wash and dry. Dry with 12 oz.
Madder, bring to boil in 1 hour and boil a few minutes, rinse, re-dye
as above, pass through warm soap bath, 2 oz., wash and dry.
(5) YELLOW
(For 1 lb.) Mordant twice in Aluminium acetate, as described for silk
(page 73), or in 1/4 lb. alum and 1-1/2 oz. chalk, steeping in cold
solution. Pass through weak bath of chloride of lime, wash, dry. Dye
with 2-1/2 lbs. weld and 1/2 oz. copper sulphate, boil for 1 hour,
then boil with soap. Or dye with 2 to 3 oz. Quercitron, which should
be brought slowly to the boil and boiled for a few minutes only.
(6) YELLOW
(For 1 lb.) Steep overnight in hot bath of 1-1/2 oz. Tannic acid, or 4
oz. Galls, wring out, dry. Work 2 hours in bath of 1/4 lb. alum and
1/2 oz. chalk, dry, pass through weak bath of chloride of lime about 1
oz., dry. Return to alum bath and repeat process, wash well, dye
slowly with 1-1/2 oz. Flavin.
(7) ORANGE
(For 1 lb.) Boil 2 oz. Annatto with 1 oz. carbonate of soda crystals
for 1/2 hour, then add to a bath containing a teaspoonful of Turkey
Red Oil, boil for 10 minutes. Take off boil, enter yarn, boil for
1-1/4 hours, let cool to hand heat, remove yarn, wash slightly and dry
quickly.
(8) BROWN
(For 1 lb.) Enter in one bath 1 oz. Cutch, in another 1/2 oz. Chrome.
Enter cotton in cutch bath, boil 20 minutes, wring out, boil 10
minutes in chrome bath. Add 6 oz. fustic or 1 oz. flavin to cutch
bath, re-enter cotton. Repeat above until the required depth of colour
is reached, finish in cutch bath to obtain deepest shade, which may be
darkened by adding 1 drachm or so copper sulphate. A greyish drab may
be got by adding ferrous sulphate. All shades of brown may be obtained
by decreasing or increasing the amount of cutch or by adding a little
logwood or fustic, in which latter case the cotton should have been
previously mordanted.
(9) BLACK
(For 1 lb.) Wash, steep overnight in hot solution of tannic acid, 1
oz., wring out without washing, work for 10 minutes in soda bath, at a
temperature of 50 deg. to 60 deg.C., 1-1/4 oz. Wring out, work in cold
solution of copperas, 1-1/4 oz., for 1/2 hour, return to soda bath for
1/4 hour. Wash, dye in bath of logwood 12 oz., madder 2-1/2 oz., and
fustic 8 oz. Enter into cold bath and raise gradually to boiling, boil
for 1/2 hour, pass through warm solution of chrome, 1 oz., wash, work
through warm soap bath.
Greys may be obtained with 1 to 5 per cent of logwood after mordanting
in a weak solution of iron.
THE ZINC-LIME INDIGO VAT
_The Zinc-lime Indigo Vat._ It will be necessary to explain these
words--Indigo blue is insoluble and cannot be used for dyeing. If
however it is "reduced" or changed to indigo white, it has, while it
is in this form, an affinity for vegetable and animal fibre. These
fibres will take it up from the solution and retain it. If they are
then exposed to the air, the oxygen acts upon the indigo in the fibre
and turns it back again to indigo blue. Various chemicals can be used
to reduce indigo blue to indigo white. I propose to describe how the
work is done with zinc dust and lime as reducing agents.
In course of time the word "vat" has been transferred from the dyeing
vessels themselves to their contents; _i.e._, the indigo dye liquor.
By "vat," therefore, we understand not only the vessel used for dyeing
indigo, but the solution of alkali salts of indigo white in water.
This definition distinguishes the _indigo vat_ completely from indigo
extract, or any other improper purposes to which indigo may be put.
The zinc lime indigo vat is better than any other for dyeing cotton
and linen. It is also very good for dyeing silk. It has many
advantages over the hydrosulphite vat, as it is not nearly so much
affected by changes of temperature and weather. It can be put to work
after a six months' rest.
The disadvantage which it shares with the copperas vat, though in a
less degree, is that there is a sediment which must not touch the
stuff during the dyeing. This is avoided by hanging a net in the vat
after the sediment has settled, or by dipping the skeins on rods.
It is essential that the indigo used should be of the best quality,
and ground to so fine a powder that it will float on water. Coarsely
ground indigo will never reduce and can be found at the bottom of the
vat unchanged. It should be so fine that no roughness is felt with the
tongue. Buy the best quality indigo ready ground, and if possible
mixed to a paste with water. A 20% paste, _i.e._ 20% of indigo and 80%
of water, is a usual quantity. If indigo powder must be used it must
be mixed to a paste very carefully, as it will, if properly ground,
fly about like dust. The easiest method of mixing is to pour the
required amount of boiling water into a jar (previously heated), then
put in the indigo. Close the vessel tightly. The steam which rises
will moisten the indigo so that it loses its tendency to fly about.
After 10 or 15 minutes it can easily be mixed with a stick. The zinc
dust should be dry and not caked.
_The lime_ should be in hard lumps. It should be bought from a
reliable chemist in a sealed container, and kept sealed till wanted.
If it is crumbling and cracking it has been exposed to damp air, and
is partly slaked already, and therefore more or less useless.
As the indigo is more quickly reduced in a concentrated solution, a
stock vat is first made and this is added to the dye vat as required.
The vessel for the stock vat should have a well-fitting lid. A
stoneware jar with a bung will do very well. To make a stock vat
sufficient to furnish a dye vat containing 15-20 gallons use:--
10 oz. Indigo 20% paste (or 2-1/2 oz. indigo pasted with
7-1/2 oz. of water),
1-1/2 oz. zinc dust,
4-5 oz. quick lime,
4-5 pints of water.
Mix the zinc dust to a paste with a little of the water, gradually add
the indigo and the rest of the water. The heat of the water should be
not less than 160 deg.F. as it will cool while the lime is being
prepared. Slake the lime in a separate vessel by pouring about 5 oz.
of water over it. When it begins to hiss and break, add more water
little by little. When all the lumps have cracked up stir till a thick
even cream is made. Add this to the other ingredients in the stock
vat. Stir well. The stock vat should have a temperature of 120-140
deg.F. It should be stirred at intervals. The vessel should be stood
in hot water to keep the temperature as near 120 deg.F. as possible.
In about 5 hours the mixture has a pure yellow colour and is ready to
add to the dye vat. (There is of course a blue-black scum of indigo on
top.)
_Preparation of the dye vat._ The vessel used should be deep and
upright so that an unnecessarily large surface is not exposed to the
air, and a sufficient space for dyeing is obtained above the sediment.
A galvanised dust bin, or a barrel (provided it is not of oak or any
other wood which contains tannin), make good indigo vats. Put 16
gallons of water in the vat at a temperature of 65-70 deg.F. In order
to counteract the effects of the atmospheric oxygen contained in the
water of the vat, additions of zinc dust and lime are made some hours
before the stock solution is added. A pinch of zinc dust and an ounce
of lime, previously slaked, should be added and the vat stirred.
Stirring must always be done gently and smoothly, every effort being
made not to take air into the vat. At the same time it must be stirred
up from the bottom so that the sediment is mixed with the liquor above
it. The best tool for this purpose is a broom stick, to one end of
which a piece of wood is nailed, like a garden rake. When all is
ready, carry the stock solution to the dye vat, and, to avoid
splashing through the air, hold it in the water of the vat while
gently pouring out half its contents. Stir up the vat and cover it
until it shows a clear yellow colour under the surface of the scum.
This may not happen for 24 hours. A good way to test the colour of the
vat is to push back the scum with the edge of a saucer or plate, then
dip it halfway into the liquor. Against its white surface the colour
of the liquor will be plainly seen. It should look like good light
ale. If the liquor is greenish and sufficient time has elapsed,
another pinch of zinc dust and a little more lime must be added as
before, and the vat again stirred, allowed to settle and again tested.
A little difficulty may be found in getting the vat to start, but once
it has worked well no difficulty will be found in starting it again.
It will work more easily as it gets older.
As indigo does not penetrate easily, every effort must be made to help
it to do so. The stuff to be dyed must be thoroughly scoured so that
no particle of grease, size, or any other impurity is present. Every
effort must be made to prevent unreduced indigo from attaching itself
to the cotton. Never begin to dye in a vat which is greenish. The
unreduced indigo will attach itself to the stuff and be wasted. Your
time will also be wasted in washing it off.
The vat should be thoroughly stirred and allowed to settle each day
before dyeing begins. When the sediment has settled, the froth should
be carefully skimmed and kept to return to the vat when the day's
dyeing is finished.
If a net is to be used it should be thoroughly wetted (if everything
goes into the vat wet it will take less air with it). The net can be
kept down by tying a few stones in a bag or an iron weight to the
centre of it. If the hanks are to be dipped on a rod this may be of
iron, or of wood suitably weighted. The hanks should not be less than
8 inches below the surface of the liquor and about 1 ft. above the
bottom of the vat. The hanks should be turned after each dip, as, if
the same end goes to the bottom each time it will be darker. A pulley
over the vat to draw out the rod or net is convenient. The dyeings can
then be allowed to drain a few seconds. Then wring each hank, shaking
it out to get the air into it. After a sufficient airing, dip again.
Many short dips with airing between will produce faster colours. Dip 1
minute, wring and air 2 minutes. Dip 2 minutes, wring and air 4
minutes. Dip 5 minutes, and so on.
As linen and cotton look so very much darker when wet than when dry, a
bit should be dried to judge if the colour is right.
Indigo can be dyed from the palest sky blue to black. The very palest
shade of sky blue is never very fast. The virtue which indigo alone
seems to possess is that, though it may become lighter with continual
use, it also becomes a clearer and more lovely blue. This is
especially so on cotton and linen, for which it is a superb dye. The
varying shades of indigo of butchers' coats, sailors' collars, and
French porters' blouses always give us pleasure.