THE SULPHUR COLORS
Nearly thirty years ago one of the French color houses put on the
market a new dyestuff which it named “Cachou de Laval”; Cachou being
the same as catechu or “cutch,” the natural brown dyestuff long known
and used in the East, and Laval being the name of the town in France
where one of its discoverers was born.
This dyestuff was made by heating sawdust, bran, turf, leaves, or
other vegetable substances with the strongly reducing alkaline salt,
_sodium sulphide_, in the absence of air. The product, dissolved in
water, makes a dark green solution which, after standing in the air a
short time, turns brown and deposits a fine brownish powder. Cotton
or linen, heated in a fresh solution of this dyestuff, is colored
green, but, when wrung out and exposed to air, the green color, which
easily washes out, changes into a very permanent, though dull and
uninteresting, shade of greyish brown.
This Cachou de Laval was not a success, commercially, because of its
poor color. It existed, however, as a chemical curiosity for some
twelve or fourteen years; then suddenly, within a few months or even
weeks of one another, all the great color houses put out a whole
series of colors—chiefly browns, blues, yellows, and blacks—all
formed, like this old “Cachou de Laval,” by the action of sodium
sulphide or, which amounts to the same thing, of sulphur and caustic
alkali, upon organic material, and all capable of dyeing cotton and
linen, in one bath, colors extremely fast to washing and generally
quite fast to light, after they have been “set” by exposure to the
air.
While in general these are known and identified as the Sulphur
colors, the different manufacturers have given special class names to
their own series thus:
Immedial (_Cassella_), Katigene (_Elberfeld_),
Kyrogene (_Badische_), Pyrogene (_Klipstein_),
Thiogene (_Metz_), Thion (_Kalle_).
These colors are used almost exclusively for dyeing cotton and linen,
when shades fast to washing are required, without first putting them
through a mordanting process. The dyeing is done in one bath, with
little more difficulty than in the case of the Salt colors described
in the last chapter; and, while not faster to light than the best of
that class, they are not nearly so liable to bleed.
On wool they are rarely, if ever, used. Wool is almost always dyed
with the acid colors in an acid bath; and nowadays the range of these
colors is so great and the best of them are so very satisfactory,
that there is hardly ever a necessity for using colors of another
class.
Neither are these Sulphur colors often used on silk, although methods
have been devised for employing them in special cases. All the animal
fibres, however, and silk especially, are very easily “tendered,”
and indeed destroyed, by heating in an alkaline solution. And so
it is very easy to spoil a skein or piece of silk by dyeing it, in
the usual manner, with these dyes, dissolved as they must be in the
strongly alkaline sodium sulphide.
The presence in the bath of glucose (corn syrup, molasses, etc.), or
of glue or gelatine, helps greatly to protect these fibres from the
action of the chemicals. But even when dyed with great care, using
glucose, and dyeing the goods for but a short time in a bath strong
in color but weak in alkali, the results are not very satisfactory,
so far as shade and lustre are concerned. They have the advantage,
however, of being extremely fast to washing, more so, even, than the
Salt colors. In general, however, silk should be dyed with the Acid
colors for ordinary work, and with the Salt colors when fastness to
washing is required. The Sulphur colors should be reserved for cotton
and linen.
On mercerized cotton and artificial silk these dyestuffs take easily
and well, when dyed in cold or lukewarm baths. The lustre, however,
of the finished goods is apt to be less than when Salt colors or
Basic colors are used.
DYEING DIRECTIONS
For cotton and linen, measure out the color and dissolve it in hot
water to which has been added twice its amount of sodium sulphide
(crystals) and a quarter or third the amount of soda ash. (In all
these formulæ washing soda may be used in place of soda ash—only
in quantities almost twice as large.) It is advisable, though
not absolutely necessary, to add also to the dye-bath one or two
tablespoonfuls of Turkey red oil—a kind of liquid soap made by
treating castor oil first with sulphuric acid and then with soda.
This prevents the formation of a dark scum on the surface of the
dye-liquor, which is likely to cause streaks in the finished goods,
hard to wash out.
Into the dye-liquor immerse the well-wetted goods, and heat them,
turning them constantly, and keeping them as far as possible away
from the air and under the level of the liquid. Just before the
boiling point is reached take out the goods, and add salt in the
proportion of, say, two spoonfuls of salt for every teaspoonful of
dyestuff used. Stir till the salt is all dissolved, put the goods
back, and continue to turn them as before, keeping the goods down
under the liquor and not allowing it to boil.
After dyeing just below the boiling point for fifteen minutes,
remove the heat, take out the goods, and—as quickly as possible—run
them carefully backward and forward through the wringer (changing
the folds of the goods each time) until the excess of dye liquor is
entirely squeezed out. Then shake them out, hang them up for fifteen
or twenty minutes in the air to oxidize and “set,” and after this
wash them thoroughly in a bath of boiling soapsuds until all the
loose color has been removed. Finally, rinse them free from soap, and
hang up to dry.
When light shades are desired, or when the goods are tender, the
dyeing can be done at lukewarm temperature, and without the addition
of salt, with no detriment to the fastness of the color. In this
case, however, much of the dyestuff will be wasted in the unexhausted
dye-liquor.
_List of Selected Dyestuffs._—
Badische— Kyrogene Brown, R R O
Kyrogene Yellow, G G, extra
Kyrogene Direct Blue, 3 B, extra
Kyrogene Black, T G O
Cassella— Immedial Bordeaux, G
Immedial Yellow Olive, 5 G
Immedial Direct Blue, B
Elberfeld—Katigen Yellow, G F, extra
Katigen Indigo, C L G, extra
Katigen Deep Black, B
Kalle— Thio Indigo Red, B
Thion Yellow, 3 G, extra
Thion Blue, B, conc.
Thion Black, G, conc.
Metz— Thiogene Brown, G R
Thiogene Gold Yellow, A
Thiogene Green, G
Thiogene Cyanine, G
Thiogene Black, M A, extra strong
These Sulphur colors are particularly strong in various shades of
black, blue, and brown. Some of the yellow shades, also, are very
fast and good. The class is deficient, however, in reds—the only one
so far discovered being Thio Indigo Red B (_Kalle_), which really
belongs to the Indigo or Vat colors, described in the next chapter,
and which does not give very powerful shades when used as a Sulphur
color. As a rule, these dyes produce shades that are softer, deeper,
and much less brilliant than those of the Direct Cotton or Salt
colors. Being usually mixed, and not simple primary, colors, they are
not very easy to dye to shade, especially as the color of the freshly
dyed goods changes considerably while it is being oxidized. On the
other hand, they give, without mixing, extremely pleasant tones, and
are all very fast to washing and, at any rate as regards the selected
colors, are fast to light.
When exposed to strong direct sunlight some even of the best of them
are liable to change their shade somewhat; but even then they will
be found to fade to nice, soft shades not out of harmony with the
original. When very great fastness to light is necessary, it may
be worth while to after-treat them as described in Chapter III, by
keeping the dyed goods for twenty or thirty minutes in a hot bath
(not boiling) containing small amounts of copper sulphate, bichromate
of potash, and acetic acid.