insoluble pigments such as chrome yellow, the ochres, vermilion
and ultramarine. Albumen is always dissolved in the cold, a process
which takes several days when large quantities are required.
The usual strength of the solution is 4 ℔ per gallon of water for
blood albumen, and 6 ℔ per gallon for egg albumen. The latter
is expensive and only used for the lightest shades. For most
purposes one part of albumen solution is mixed with one part of
tragacanth mucilage, this proportion of albumen being found amply
sufficient for the fixation of all ordinary pigment colours. In
special instances the blood albumen solution is made as strong as
50 per cent., but this is only in cases where very dark colours are
required to be absolutely fast to washing. After printing, albumen thickened
colours are exposed to hot steam, which coagulates the
albumen and effectually fixes the colours.
Formerly colours were always prepared for printing by boiling
the thickening agent, the colouring matter and solvents, &c., together,
then cooling and adding the various fixing agents. At the
present time, however, concentrated solutions of the colouring
matters and other adjuncts are often simply added to the cold
thickenings, of which large quantities are kept in stock.
Colours are reduced in shade by simply adding more starch or
other paste. For example, a dark blue containing 4 oz. of methylene
blue per gallon may readily be made into a pale shade by adding
to it thirty times its bulk of starch paste or gum, as the case may
be. Similarly with other colours.
Before printing it is very essential to strain or sieve all colours
in order to free them from lumps, fine sand, &c., which would inevitably
damage the highly olished surface of the engraved rollers
and result in bad printing. livery scratch on the surface of a roller
prints a fine line in the cloth, and too much care, therefore, cannot
be taken to remove, as far as possible, all grit and other hard particles
from every colour.
The straining is usually done by squeezing the colour through
fine cotton or silk cloths. Mechanical means are also employed
for colours that are used hot or are very strongly alkaline or acid.
STYLES or PRINTING
The widely differing properties of the hundreds of colouring
matters now on the market give rise to many different styles of
textile-printing. Generally speaking, these fall into the following
four great divisions:-
(I) Direct printing.
(2) The printing of a mordant upon which the colour is afterwards
dyed.
(3) The discharge style.
(4) The resist or reserve style.
The fact that each of these divisions is further sub-divided into
many smaller divisions renders it out of the question to give more
than a few typical examples of the various styles they include.
(I) Direct Printing.-This style is capable of application to almost
every class of colour known. Its essential feature is that the
colouring matter and its fixing agent are both applied to the fabric
simultaneously. In some instances the fabric requires to be previously
prepared for certain of the colours used along with those
characteristic of the process; but this is one of many cases where
two styles are combined, and it must be classed with the one which
it most resembles.
(a) Application of Mordant Dye-Slujs.-Mordant colours include
both artificial and natural dye-stuffs (see also under DYEING), the
most important of all being alizarine, an artificial preparation of
the colouring-principle of the madder root. Vl/ith different metallic
oxides alizarine forms different colour-lakes all exceedingly fast to
light and soap. Aluminium mordant gives red and pink lakes;
iron mordant, purples and lavenders; chromium yields maroons;
and uranium gives grey shades. Mixture of iron and aluminium
produce various tones of chocolate and brown.
In addition to alizarine the following are a few of the more
important mordant dye-stuffs employed in textile-printing:-
Alizarine orange with aluminium and chrome mordants for
orange and warm brown shades respectively; alizarine bordeaux,
with alumina, for violets; alizarine blue with chrome and zinc
for quiet blue shades; coeruleine and alizarine viridine for greens
and olives with chromium mordants; gallocyanine, chrome
violet blue, alizarine cyanines, &c., with chromium for various
shades of blue and violet; alizarine yellows and anthracene
brown for yellows and fawn shades respectively with either aluminium
or chrome mordants. The natural dye-stuffs belonging to
this series are chiefly: logwood, with chromium and iron mordants,
for blacks; Persian berries and quercitron bark, with
aluminium tin and chromium mordants, for colours ranging from
brilliant yellow to quiet old golds and browns; catechu, with
chromium, for very fast dark browns; and, occasionally, in mixtures,
sapan-wood, peach-wood, Brazil-wood, and divi-divi extracts
with any of the above-mentioned mordants.
The mordants are mostly in the form of acetates which .are
stable in the cold but decompose.during the steaming process, and
combine as hydroxides with the colours, forming and fixing on the
fabric the insoluble lake.
Alizarine reds and pinks are the most complicated of the mordant
colours. requiring for their proper production the addition
of brightening agents, such as oxalate of tin, oils, tartaric acid,
and also acetate of lime. This also applies to alizarine orange,
but all the other colours are very simple to compound and are
stable for along time after making. Reds, pinks and oranges
are best prepared freshly each day; their constituents are liable
to combine if the colour stands twenty-four hours before printing.
The following types of recipes will give some idea of the way in
which colours are mixed:—
Red. 612 gallons thick starch and tragacanth paste.
114, , alizarine (20 per cent. commercial paste).
1 ,, nitrate of alumina, 18° Tw.
12 ,, acetate of lime, 28° TW.
14 ,, oxalate of tin, 10° Tw.
12 ,, 10 per cent. solution of tartaric acid.
Pink. 612 gallons starch-tragacanth paste.
1, , blue shade alizarine (20 per cent. paste).
114 ,, sulphocyanide of alumina, 18° TW.
38 ,, acetate of lime, 28° TW.
14 ,, oxalate of tin.
12 ,, citrate of alumina, 40° TW.
For reds and pinks the nitrate, sulphocyanide and citrate of alumina are generally preferred in practice to the acetate though the latter is also largely used. Oranges from [alizarine orange are made similarly.
Purple. 918 gallons starch paste.
18 ,, blue shade alizarine, 20 per cent.
12 ,, acetic acid.
18 ,, acetate of lime, 28° TW.
18 ,, acetate of iron, 24° TW.
gallons paste.
Alizarine Blue. 12 ℔ alizarine blue shade (powd.).
(Light Shade.) 1 gallon water.
312 ,, thick paste.
112 ,, acetate of chrome, 40 TW.
Logwood and other natural colours are specially boiled.
Logwood Black.
15 lb starch.
British gum.
10 if
412 gallons water.
34 , , acetic acid.
112, , logwood extract, 48 TW.
38 , , quercitron extract, 48° TW.
Boil, cool and add:-
12 ℔ red prussiate of potash.
14 gallon water.
2 ,, acetate of chrome, 40° TW.
2 oz. chlorate of potash.
Quercitron Yellow.
112 gallons quercitron extract, 48° TW.
612 ,, water.
11 lb starch.
Boil, cool and add:—
34 gallon acetate of chrome, 30° TW.
The proportions here given are liable to variations according to circumstances. Indeed, no two works employ quite the same recipes, although the proportion of mordant to dye-stuff is pretty generally known and observed. After printing, the goods are dried, steamed for one hour, and then washed and finished. (b) Application of Basic Aniline Dye-Slujs.-These colours all form insoluble lakes with tannic acid; hence tannic acid is the common fixing agent of the group. Arsenic in combination with alumina also gives basic-colour lakes, but their poisonous character and their inferior fastness to most reagents considerably limit their application. The more important basic dye-stuffs are: methylene blue, methyl violet, rhodamine, auramine yellow, safranine emerald green and indoine blue. Most of them are fairly fast to soaping, but towards the action of light they vary a good deal, methylene blue being perhaps as good as any, and the malachite greens the least stable. Their application is simple. A solution of the colouring matter is added to the requisite quantity of starch paste or gum, and, when well mixed in, the tannin is added in the form of a solution also. If desired they may be boiled up like the extract dye-stuffs (logwood, &c.), but this is not necessary unless large quantities are required, when it would be more convenient to boil the whole at once than to mix small batches by hand.
