RESIST AND DISCHARGE STENCILLING
Travelers in Japan inform us that, with their customary ingenuity,
the natives there have developed the use of stencils to a point which
quite matches the best achievements of our modern calico printers,
even though backed by good dyeing chemists. When a young lady there
wishes a new dress, she will draw, perhaps with the help of her best
young man, and certainly with the advice and criticism of her family,
her favorite design on a piece of brown paper, cut it out in stencil
form, and send it to the local dyer, with the proper amount of calico
or silk or what not, to be properly applied.
Now, in most cases the dyer is instructed to put the pattern on the
cloth in colors, blue, black, red, yellow, or mixed shades, and this
he does, much as my readers were taught to do in the last chapter, by
painting on a stencil paste, to be fixed later by steaming.
The Japanese dyer, by the way, has a great advantage over the
American craftsman in his steaming apparatus. No matter how small his
place, or how poor his equipment, he always is provided with a neat
and satisfactory steam chest, consisting of a copper pot set in a
brick or stone fireplace, to hold the boiling water, and above it, a
close-fitting box with sides made of lacquered paper, double jacketed
to avoid condensation in cold weather, which can be kept full of dry
steam for hours at a time, and in which the stencilled goods can be
steamed thoroughly and well without fear of spoiling them.
Sometimes, however, the color is to be applied in another way; the
cloth itself is to be colored blue or red or black, and the pattern
is to be light, either pure white or some light color on a dark
background.
The Japanese dyer, from time immemorial, has known how to do this
properly, by means of a “Resist.” He prepares a resist paste which he
carefully applies to the cloth through the stencil. This is allowed
to dry, the cloth is then dyed, and, after the color is properly
fixed, it is all thoroughly scrubbed, and the paste, washing off,
leaves the cloth, underneath, in its original color.
_Resist Stencil Paste._—This process of resist, ancient as it is, is
used in Japan to this day, and many, indeed most, of the stencilled
towels and piece goods that come from there are done in this way. It
has the advantages, especially for the craftsman, over the Direct
Color process, in that the color, being applied in a dye-bath, can be
fixed readily and uniformly, without the bother and uncertainty of a
steaming process. Through a friend, a well-known dyeing chemist, who
has travelled in Japan, I learned the composition of the Japanese
Resist Paste. They mix rice flour, wheat bran, and a little quicklime
(the calcium oxide of the chemist) with water and boil it to make
a paste. This they strain, and then they stir in some powdered
carbonate of lime (powdered chalk), which thickens and gives some
body to the mixture. The paste thus formed is applied, as a rule, not
with a brush but with a flat wooden instrument or spatula, with which
the paste is laid on as with a trowel, and further, to get the dead
white effects so commonly noticed, the paste is put on the back of
the cloth as well as on the front.
My friend also explained to me how the Japanese were able to get
irregular shaded effects with their stencil work, and at the same
time to furnish such beautiful and intricate hand-made work, at
such absurdly low prices. These goods are made of very thin porous
materials, and the dyer applies with his trowel the thick resist
paste, through the stencil, to one piece after another, laying each
one, as fast as it is stencilled, carefully on top of the previous
one, until a pile has been formed of ten or more separate pieces.
This pile is pressed very tightly together, and then the dyestuff,
as, for instance, Indigo in solution and thoroughly reduced, is
poured on to this mass of goods, soaking through from one to the
other, but always kept out of the white parts by the double coating
of thick paste.
After a few minutes these pieces are carefully taken off, one by one,
exposed to the air until oxidized, and then thoroughly washed until
the paste and loose color have all disappeared. For an example of
Japanese resist stencil work, dyed in an iron spring, see Plate III.
[Illustration: PLATE V. JAPANESE TOWELLING DYED BY IMMERSION IN IRON
SPRING. THE WHITE PATTERN IS CAUSED BY RESIST STENCILLING]
_Resist Stencilling with Sulphur Dyes._—Without lavishly copying
the Japanese practice it is possible to get very interesting results
by using suitable dyestuffs with a simpler paste.
The most useful dyes for this purpose are the Sulphur dyes, which,
as the student will remember, can be applied in the cold, with very
short exposure to the dye-liquor, and are fixed firmly by exposure
to the air, giving results fast to light and extremely fast to
washing. A paste made from wheat flour, thickened a little with an
inert powder, like powdered chalk or zinc oxide, will work fairly
well, acting as a purely mechanical protection to the fibre. But much
better results can be obtained by adding to the paste as much as it
will absorb of the easily soluble chemical, zinc sulphate, which acts
chemically in resisting the action of these particular dyestuffs.
The Sulphur colors, as before explained, are kept in solution in
the dye-bath, by the presence of sodium sulphide, and when this is
absent or is destroyed by any cause, the dyestuff is precipitated
as an insoluble, inert powder. Now, when zinc sulphate comes in
contact with sodium sulphide it at once decomposes the latter,
forming a white precipitate, zinc sulphide, which has no action at
all on either dyestuff or cloth. Accordingly a paste containing zinc
sulphate has far greater efficiency as a resist than any mixture that
acts purely mechanically.
Resist stencil pastes can be obtained, in tubes, at moderate prices,
but can also be readily prepared by making not too stiff a paste,
with wheat flour thoroughly boiled with a saturated solution of zinc
sulphate instead of with water, and then stirring into this paste
some powdered chalk or zinc oxide, until of the proper consistency
for stencilling.
To use this paste, the cloth, as usual, should be washed free from
dressing, and after being smoothed with a hot iron, should be
slightly dampened. The paste is then brushed through the stencil on
to, and into, the cloth, which is then allowed to dry. The dye-bath
should then be prepared of Sulphur dyes carefully dissolved, in a
separate cup or saucepan, in a hot solution of sodium sulphide and
sodium carbonate (soda), and added to cold water in the dye-bath.
A few drops of “Turkey red oil” added to the dye-bath helps to
prevent a thick scum from forming on top of the liquor, while the
addition of a tablespoonful of salt dissolved in a little hot water
helps the rapidity and depth of the dyeing.
Plenty of color should be used excepting for very light shades, for
the dyeing should be done just as quickly as possible. For silk some
syrup should be added.
The stencilled cloth is then quickly moistened in cold water, placed
in the dye-bath, kept there two or three minutes, below the level of
the liquid; it is then taken out, the liquor drained off, and after a
minute or two, wrung off; the cloth is then shaken out, and exposed
to the air, for some ten minutes, to set the color. After this it is
well washed in a boiling soap bath, and, as the paste washes out, the
stencilled pattern will show light against the dark background.
The whiteness of the pattern depends, of course, upon the skill
with which the paste has been applied, and the care taken to prevent
it from washing off before or during the dyeing process. It is
difficult, though not absolutely impossible, to get as sharp and
clear-cut results as those of the Japanese, for instance. But, on the
other hand, with a dark background it is often, indeed generally,
more pleasing to have the white patterns softened and not standing
out too vividly.
In our laboratory we have had considerable success with this process.
And some of our friends and students have used it with very good
results upon articles of clothing, which, made of linen, calico,
etc., must be fast to severe washing as well as to light.
Of course, it is perfectly easy to alter the color of the background,
as in other classes of resist work, such as Tied and Dyed work, for
instance, or Batik, by either starting off with colored cloth which
is protected all through by the resist paste, or else by covering
the stencilled and dyed goods, afterwards, with some shade which
will soften and harmonize both pattern and background. For this
covering shade, which need not be very fast to washing, but must be
distributed uniformly over the whole cloth, the student will find the
Salt colors very useful.
_Discharge Stencilling._—Though it is not certain whether this
process is known to, and used by, the Japanese, it is not a difficult
matter, with modern dyes and modern chemicals, to get interesting
results with it. There are two distinct and separate ways open to the
dyer for discharging, i.e., destroying his dyestuffs, whether they
are dyed on cloth, or whether, as is not infrequently the case with
amateurs, they are present as a stain on his hands and fingers. In
each case, however, care must be taken, as may easily be imagined, to
use such chemicals as will spare the materials, whether cotton and
linen, or nails and skin, while attacking the coloring matter.
(a) _Discharge by Oxidation. Chlorine Compounds, Bleaching Powder,
etc._—In the first place, chemists have long known that certain
chemicals, more particularly the powerful gaseous element known as
chlorine and certain of its compounds, have the power of permanently
destroying coloring matters by oxidizing or burning them.
At first this was done by using chlorine itself, or a water solution
of chlorine. Later, however, it was found that on passing chlorine
into some caustic alkali, like quicklime, or caustic soda, or caustic
potash, these would absorb immense quantities of chlorine which would
be again given out, as desired, on the addition of acid, or even,
though very slowly and gradually, by the action of the carbonic acid
gas in the air.
The lime compound, which contains more chlorine than the others, and
has the great advantage of being dry, has long been known as chloride
of lime or as bleaching powder, and has been, and is, commonly
used from one end of the world to the other as a quick, ready,
cheap source of chlorine either for bleaching or for disinfection.
The potash and soda compounds, known respectively as Labarraque’s
solution and Javelle water, are less active and powerful than
bleaching powder, but have the same general properties.
Over a hundred years ago, very soon after the discovery of the
bleaching properties of these compounds, chemists began to use them,
not only for decolorizing and whitening raw cotton and linen cloth,
but also for discharging the color in patterns from dyed goods. The
process was not a difficult one, and is used to this day to some
extent in the calico printing mills. The cloth is first dyed to
shade, fixed, and dried. The pattern is then printed on with a paste
containing some solid organic acid, like citric acid or tartaric
acid, dissolved in it. After drying, the printed cloth is passed
through a bath of bleaching powder in water, possibly with a little
weak alkali added, to be sure that no free chlorine is present;
and wherever the bleaching powder meets the acid the cloth is
decolorized, but the rest of the cloth comes out of the bath without
being much, if at all, altered in color. Of course, on coming out
of this bath the cloth must be thoroughly washed to get rid of any
traces of chloride of lime, which otherwise, on exposure to the air,
would play havoc with the rest of the colors.
This process worked very well with the old vegetable dyes, and,
every now and then, some craftsman, of an experimental turn of mind,
revives it for stencil work. The dyed cloth is stencilled with a
paste made of wheat flour boiled with a saturated solution of citric
acid, it is dried, and then passed through a bath of bleaching
powder in water, say two or three tablespoonfuls to the gallon. It
is generally best to stir in a few drops of a soda solution to the
bath, till all smell of chlorine has gone, or else the background may
be affected. The stencilled cloth is dipped in this bath, and kept
there for a few minutes, until the bleaching process is well under
way, and then taken out, and washed in hot soap and water, and rinsed
well.
_Advantages and Disadvantages of Bleaching Powder Discharge._—The
chief advantage of this process is that it is very cheap and the
materials can be bought at almost any grocery. The disadvantages are,
however, important. As long as it is confined to easily discharged,
comparatively fugitive, colors, it will destroy the color all right
in the stencilled parts, although the bleaching powder bath is apt
to attack the color in the body of the cloth, and the outlines of
the pattern are apt to be soft and irregular because of the escaping
chlorine, where the citric acid is acting.
When, however, very fast dyes are being used, as for instance, the
Vat colors or, indeed, a great many of the best dyes in all the
classes, the action of chlorine is very slow, and slight, and, in
order to really destroy the color both the acid and the bleaching
powder will often have to be so strong that the chlorine set free
will destroy the fibre as well. For the term “fastness to light”
implies, as a rule, fastness also to oxidation in general, and dyes
like the best modern ones which will let the cloth rot away from
under them, when long exposed to the weather without changing color,
are very apt also to keep their color, even when the cloth is _burnt_
away from under them by the action of chlorine.
Accordingly, this process is distinctly one that needs careful
experimentation before it is tried on any important piece of work.
There are plenty of dyestuffs among the Salt colors, and also among
the Sulphur colors, which discharge well with chlorine. And the
calico printer, working, as he generally does to this day, with
comparatively fugitive dyes, and weighing accurately both acid and
bleaching powder, can generally get good results with it. But there
is always the disadvantage, that the least excess of chlorine will
attack and tender the cloth, and the better the dyestuff, as a rule,
the stronger the oxidizing agent must be to discharge it.
(b) _Discharge by Reduction, Hydrosulphite, etc._—The wary craftsman
will find the process much less dangerous to the cloth, and not much
more difficult, if instead of trying to _oxidize_ the dyestuff, he
attempts to discharge it by _reducing_ it; or, in other words, if
instead of trying to burn it out, he tries to take the oxygen away
from it.
It so happens that in a vast majority of cases a dyestuff becomes
decolorized by reducing it, just as well as by oxidizing it. There
is, however, a difference. When the color is oxidized, it is burnt up
and destroyed forever. When it is reduced, however, it is, in many
cases, only decolorized and not destroyed; and on standing in the air
it is apt to take up oxygen again, and to regain some, at least, of
the original color. On the other hand, while any oxidation process is
liable to attack the cloth as well as the color, the reducing agents
now in use have no effect upon the materials, even when powerful
enough to act on the very fastest dyestuffs.
As before mentioned, the most satisfactory reducing agent at present
known to dyers is hydrosulphite of soda, and this can be incorporated
in a paste, and used for discharge stencilling. It is, however, as a
rule, more satisfactory to use the more expensive, but more permanent
hydrosulphite compound, described, in the last chapter, as acting
only when heated.
The reducing stencil paste can be easily made by mixing with some
“gum dragon” or flour paste, as much as it will hold of a saturated
solution of the “Stencil Salt.”
The student should experiment with the different dyes and classes of
dyes before attempting a serious piece of work; but in general, all
the Salt colors and the Acid colors will discharge readily with this
paste, and remain colorless. The Vat colors and the Sulphur colors
can also be reduced to colorless compounds, but it is not always
easy to wash them out of the cloth after the reduction, and, if they
remain in it, they are apt to regain their color, on standing in the
air.
The dyed cloth, carefully washed and pressed and dampened, is
stencilled with the above paste and allowed to dry. When dry it is
steamed, as described in the last chapter, and it will be noticed
that when a certain temperature is reached the color will be
discharged. As soon as possible afterwards the cloth is to be washed
in a hot soap bath to remove the reduced color compound (which, as
a rule, has little affinity for the cloth) and to get rid of the
paste. Then the cloth is dried and finished.
When trying this process with the Vat dyes it is best to soak the
cloth directly after steaming, and before soaping, in a warm bath
containing a little free caustic soda (remember this is apt to burn
the fingers) because the reduced colors of this class are not, as a
rule, soluble in water, and are apt to oxidize again in a soap bath.
_Results._—In following up these various experiments in our
laboratory we have not used this process in much as the Resist
stencilling, but there is no reason why it should not give just as
good results. Indeed, the craftsman will probably find, after a
little practice, that it is easier to get clear white patterns with
this than with the other. It has the disadvantage of requiring the
rather bothersome steaming process, which reduces its value for many
purposes. Still it will often be found that simply ironing the dried
stencilled cloth with a hot flatiron, with a damp cloth between, will
cause the reduction to take place quite satisfactorily.
The chief advantage of this process over the other is that, as the
dyeing is done before and not after the stencilling, it is possible
to get the exact shade of background required. While, in the resist
stencilling every minute, almost indeed every second that the
stencilled goods are left in the dye-bath, is liable to obscure
the pattern. And it is hard to get first-class results, as regards
fastness to rubbing and washing, and it is impossible to match
shades, when working so hurriedly.
Then, too, this discharge process permits the use of almost every
color on the list, while the resist process practically confines the
craftsman to the use of the Sulphur dyes only.
Those who are interested in this line of work are advised to try
these two processes upon silk, where very beautiful and interesting
effects can be produced with but little difficulty. The resist
process, using Sulphur colors, gives quiet soft tones on silk, fast
to the hardest kind of washing. But brighter shades, equally fast to
light, and fairly fast to washing, can be made with the discharge
process by using Salt colors.
For ordinary work the Acid dyes, of course, would be used, and these,
too, as a rule, discharge readily.