|The Secret of Everyday Things|
|by Jean Henri Fabre|
|Fascinating conversations with Uncle Paul reveal the mysteries behind the dyeing and weaving of cloth, the lighting and heating of homes, the processing involved in bringing oil, coffee, tea, spices, and other foodstuffs to the table, and the power of water in all its manifestations. Excellent as follow-on to The Story Book of Science. Ages 11-14 |
DYEING AND PRINTING
RRIVED at this point, the cotton cloth is ready to
receive the colors. This operation involves the use of
means so varied and technical knowledge so above your
understanding that I should not be understood if I
undertook to enter into some of the more elaborate
"I supposed, on the contrary," said Claire, "that it
was a very simple thing and that the colors were put on
the cloth with a paint-brush just as I should do,
though not very well, on a sheet of paper."
"Undeceive yourself, my dear child: the paint-brush has
nothing to do with printed cottons, nor yet with the
other kinds of goods embellished with colors. Done with
a paint-brush, the designs would not be lasting, but
would disappear with the first washing. The slightest
rain would make the colors run and would turn them into
horrible shapeless blots. To resist water, and
sometimes vigorous washing with soap, the colors must
penetrate the fabric thoroughly and become embodied in
"Let us see how this result is arrived at, taking black
for an example. This color is obtained in various ways,
notably with ink, the same that we use for writing.
Well, if we immersed a strip of white material in this
liquid it would come out black,
 but the color would have no staying power. A little
rinsing in water would remove most of the ink, and the
small amount remaining would give only a pale tint,
very insufficient and soon washed out. In order to give
a deep and lasting black the ink, when it is applied to
the fabric, must be in an unfinished state, and it must
finish itself in the cloth; the ingredients of which it
is composed must mingle and become ink in the very
substance of the threads. Under these conditions the
black, made on the spot and permeating the minutest
fibers of the cotton, acquires all the desired fixity
and intensity. Let us, then, before going further,
examine the ingredients of which ink is composed.
"There are found growing on oak-trees certain globular
formations of about the size of a billiard ball and
with the appearance of fruit. But they are not really
fruit; they have nothing in common with acorns, the
real fruit of the oak. They are excrescences caused by
the sting of a tiny insect known as the gall-fly. This
insect stings the leaf or tender twig with a fine
gimlet that arms the tip-end of its stomach, and in the
microscopic incision it deposits an egg. Around this
egg the sap of the tree gathers, finally forming a
little ball which by degrees becomes as hard as wood.
The insect hatched from the egg develops and grows in
the very heart of this ball, whose substance serves
 it as food. When it has grown strong enough it pierces
the wall of its abode with a small round hole through
which it escapes. That is why you see most of these
balls pierced with a hole when they fall to the ground
toward the end of autumn. These round excrescences are
called gallnuts or oak-apples, and they furnish one of
the ingredients of ink, one of the materials used for
"The other ingredient is green copperas. At the
druggist's you may have seen a substance looking
something like broken glass of a light green color with
spots of rust. That is green copperas. It is obtained
by dissolving iron in an excessively corrosive liquid
known as oil of vitriol or sulphuric acid. This
terrible liquid, so dangerous in inexperienced hands,
dissolved iron as easily as water dissolved salt or
sugar; and in this solution, after a certain time,
crystals are formed. It is this crystallization that
give us our green copperas, a substance having none of
the dangerous qualities of the oil of vitriol used in
making it, but one that can be handled without the
least risk, though its taste is most disagreeably tart.
This substance dissolves very readily in water.
"That is all that is needed for making ink. Let us boil
a handful of pounded gallnuts in water; we shall obtain
a pale yellowish liquid. Also, let us dissolve some
copperas in water, and the latter will turn a very pale
green with a yellowish tinge. What will happen on
mixing the two liquids, one yellow and the other green?
Nothing very remarkable, it would seem. And yet no
sooner do these two liquids
 mingle than there is produced a deep black, the very
color of ink."
"And so the ink comes all of a sudden." said Maria.
"Yes, the very instant the gallnuts and the copperas
meet in the water that holds them in solution. If ink
for writing is desired, however, a little different
method must be followed so as not to have an excess of
water, which would weaken the color. To the liquid
resulting from boiling the gallnuts there would simply
be added the undissolved copperas with a little gum to
give brilliance to the ink. I have gone out of my way
in describing to you this mingling of two liquids in
order to show you the more clearly how the union of two
substances, each having little or no color, can produce
a color totally unlike either of the original shades.
From two liquids, one a pale yellow, the other a pale
green, you have just seen ink spring into being with
startling suddenness. Remember this phenomenon, for it
will explain certain results of dyeing that are very
astonishing to the uninitiated. Bear in mind that
sometimes perfectly colorless substances can produce
magnificent colors by being united.
"Now that we know how ink is made, let us return to the
subject of dyeing black. We put a piece of percale to
soak in water in which gallnuts have been boiled; then,
when it is well saturated, we take it out and dry it.
What, now, will be its color!"
"It will be the color of the gallnut water," answered
Claire; "that is to say, a pale and dirty yellow."
 "Right; but if the fabric thus saturated is dipped into
a solution of copperas, what will happen?"
"That is not hard to guess," was the reply. "The
copperas, finding gallnut dye on the surface and in the
texture of the cloth, all through it in fact, will
immediately form ink, which will color the percale
"And more than that," added Marie, "the dye will
penetrate the goods evenly in every part, since the
saturation with gallnut water extends to the very
tiniest thread of the material."
"Yes; and so you see that in this way the black dye is
formed on the spot, in the very heart of the cotton
threads. Thus we obtain a fast color, all the necessary
conditions being complied with.
"A great many other colors—red, violet, brown,
yellow, lilac, no matter what—are produced in
similar fashion. First the material to be dyed is
saturated with a solution that will develop the desired
color, or make it spring into existence, on
encountering another solution, and will set the color
by making it one with the fabric itself. This
preparatory substance which in a second operation is to
mix with the dyestuff so as to develop and fix the
color is called the mordant and varies in kind
according to the tint desired, so that by changing the
mordant different colors may be obtained with one and
the same coloring matter."
"In the same way you have just explained to us," said
Marie, "we get cloth dyed all one color. I should like
to know how patterns of several colors on a white
ground are made."
 "That is done by printing or stamping. Imagine a small
wooden block or board on which is engraved in relief
the design to be reproduced. Clever engravers skilled
in all the details of ornamental design prepare these
blocks, which are sometimes veritable masterpieces of
art; and it is these that constitute the
calico-printer's all-important equipment.
"To take a simple example, let us suppose the workman
proposes to put a black design on a white ground. On a
large table in front of him he has the piece of percale
which unrolls as he needs it; in his right hand he
holds the printing-block. The engraved design, which
stands out in relief, he moistens slightly with a fine
solution of gallnuts, and then applies the block to the
goods. The parts thus touched are the only ones
impregnated with this preparation, the rest of the
percale remaining as it was before. He continues thus,
each time dipping the engraved face of the block into
the gallnut preparation, until the piece of cloth has
received the impression throughout its entire length.
"That done, all that is necessary is to dip the goods
into a solution of copperas to make the design appear
in black, since the ink forms wherever the wooden mold
has left a deposit of gallnut water, all other parts
"It is simpler than I had thought," said Claire, "and
much simpler than using a paint-brush, as I supposed at
first must be the way."
"The operation can be made still simpler. As a rule the
coloring matter and the mordant, that is to say the
substance that brings out the color and fixes
 it, act only under the influence of the heat.
Accordingly, the process is as follows. The two
ingredients, mordant and coloring matter, are mixed
together and reduced to a fine pap with which the
engraved surface of the block is moistened and then
immediately applied to the fabric. The preparation thus
deposited gives only one color, one alone, determined
by the nature of the mordant and the coloring matter.
If the design is to be multicolored, as many blocks
must be used as there are tints, each block
representing only the part of the design having the
color it is to imprint on the goods. Thus the piece of
percale passes through the workman's hands once for
red, again for black, a third time for violet, in fact
as many times as there are colors in the design,
however little they may differ from one another."
"It must be a very delicate piece of work," remarked
Marie, "to put the different parts of the design
exactly in the right place so as to get from them all a
pattern with the various colors joining perfectly and
"The calico-printer's skill makes light of this
difficulty. The design comes out as clear as a painter
could make it with his brushes. To complete the
description in a few words, when all the colors have
been applied, the fabric is removed to a closed room
where it receives a steam bath. Heat and moisture
aiding, each dye mixes with its mordant, which
incorporates it with the fabric, and beautiful bright
tints spring forth as by enchantment where the engraved
blocks had left only a sorry-looking daub."
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