PRINCIPLES OF DYEING FABRICS
ALL-OVER DYEING
The simplest process of dyeing a fabric consists in submerging it in a
solution of dye, known as a "dye-bath," and allowing it to extract or
exhaust the color from the bath. It is necessary that there be an
attraction or affinity between the fiber of the fabric and the dye in
solution. All parts of the fabric must be given equal opportunity to
extract the dye in order that a uniform color or "level" dyeing be
obtained.
[Illustration: {USING A DYE-BATH} {p. 35}]
To accomplish this end experience has found that a few simple things
must be observed. These have to do with, (1) the preparation of the
fabric for dyeing, (2) the making of the dye-bath, (3) the handling of
the fabric while in the dye-bath, and (4) the handling of the fabric
after the dyeing.
1. _The Preparation of the Fabric._ The fabric must be clean. A spot
of grease or other soil allows that part of the fabric less
opportunity to extract color from the dye-bath, with the result that
the dyeing is not level. Thorough washing with soap and warm water
followed by a good rinsing will remove most spots. The methods of the
dry cleaner will be necessary for others.
All sizing must be removed. Sizing consists of substances such as
clay, flour, starch, gum, oil, tallow, soap, etc., put into the fiber,
either before or after weaving, for the purpose of giving weight,
body, strength, stiffness, softness, finish, or other desired quality.
Some sizing prevents the extraction of color from the dye-bath. In
other cases the sizing itself absorbs a large share of the color, and
later when the sizing is removed by washing this color goes with it.
Vigorous washing with soap and hot water, followed by rinsing, will
remove most sizing. A fabric which suffers injury by the removal of
its sizing is not suitable for dyeing.
Previously dyed fabrics are often uneven in color due to spotting and
fading. Level dyeing cannot be done over such color. The practice of
the professional dyer is to remove or level this color before
attempting further dyeing. This often calls for skill beyond that of
the inexperienced worker. Sometimes prolonged boiling in strong soap
suds will accomplish this. Many colors will also yield to hot
hydrosulphite solution followed by a good rinsing.
Of course where goods have been previously colored there are
limitations as to the colors that may be obtained by additional
dyeing. For example, blue goods cannot, without the removal of the
blue color, be dyed yellow but may be dyed green or purple or a deeper
blue. Yellow goods cannot be dyed pink, but may be dyed orange,
green, brown or black. This will be discussed more fully later.
Some fibers are hard and harsh and resistant, like crash and most new
cotton cloth. This is due to the presence of gums, resins, waxes and
other impurities, substances which either attract dyes or else prevent
their taking the fiber. It is not possible to dye such goods
successfully without first rendering the fibers soft and absorbent.
This may be accomplished by prolonged boiling in washing soda.
Repeated washing and exposure to air will also do it, hence old cotton
usually dyes well. Technically there are elaborate and carefully
carried out chemical processes of preparing cotton cloth for dyeing,
and entire mills are busy doing this one thing.
The Javanese and other Oriental peoples purchase cotton cloth from
Europe and treat it for many days, alternately soaking in oil and
boiling in lye from ashes, then exposing to the hot sun. This process
is repeated until the cloth is soft and absorbent and suitable to
receive color decoration.
The cloth should always be thoroughly wet before putting it into the
dye-bath. This should be done in water of the same temperature as the
dye-bath.
It may be briefly mentioned here that a fabric must sometimes be given
a treatment with some chemical, called a mordant, before it will
exhaust certain dyes from the bath and be properly dyed.
2. _The Making of the Dye-Bath._ For simple dyeing, as mentioned at
the beginning of this chapter, we must observe the following things:
The dye-bath must be sufficient in quantity to cover the goods well
and to permit of their being worked thoroughly during the process of
dyeing.
For the "dye-vat," or container for the dye-bath, use preferably a
large graniteware pan or stone jar. Metal dishes, especially iron, are
sometimes injurious. Professional dyers often use vats of copper,
brass or wood.
Soft water is preferable, and it should be free of sediment. The
presence of iron in water is most injurious as it dulls, or "saddens,"
the shade of most colors. A hard water containing lime should be
purified or softened. Lime sometimes causes uneven dyeing.
The dye must be completely dissolved in the water. If specks of
undissolved dye are present there will be a spotted uneven dyeing. It
is best to dissolve the dye in a small amount of water in a separate
dish and then strain it. This should be added to the dye-bath a
portion at a time during the dyeing. The reason for this will appear
later.
The temperature of the dye-bath has much to do with the dyeing. There
is no general rule applicable to all dyes. Each dye is usually
accompanied by directions as to the temperature to be used. In general
it may be said that all dyes work better in warm or hot solution. Some
dyes require prolonged boiling; in other cases boiling is positively
injurious to the dye. Sometimes a definite temperature below the
boiling point must be maintained. Sometimes the temperature is raised
or lowered during the dyeing. In all cases the temperature should be
kept the same in the different parts of the bath, otherwise the dyeing
will be uneven.
Many dyes, while most successful at high temperature, work very well
in moderately warm, or even cold solution. This is of very great
advantage in pattern dyeing, as in batik work, where the wax forbids a
high temperature.
The composition of the dye-bath is not often as simple as we have
indicated. Usually the dyer adds one or more other chemicals to assist
in dissolving the dye, to control the rate of absorption of the dye by
the fabric, or for some other purpose.
Some of the finest dyeing is done in baths so complex and with
operations so exacting in care that only the trained professional with
his elaborate equipment is able to undertake it.
3. _The Handling of the Fabric in the Dye-Bath._ Since all parts of
the fabric must have equal opportunity to be dyed, in order that a
level dyeing be obtained, it is absolutely necessary that the goods be
worked as long as they remain in the dye-bath. This working must be
thorough and continuous without interruption. This cannot be
emphasized too much.
Let us think what happens if this rule is not heeded and the goods
stand a few minutes in the bath. Some parts of the fabric will lie
inside the folds of other parts and, having access to only a small
part of the dye-bath, will soon exhaust all of the dye available, a
condition known as "local exhaustion." Meanwhile other parts of the
fabric more favorably situated will continue to absorb dye. More
uneven dyeing in schools and homes is due perhaps to this cause than
to any other.
Constant working of the goods keeps the dye that yet remains in
solution uniformly distributed in the bath so that all parts of the
fabric are absorbing dye alike. It also maintains what is equally
essential to level dyeing, a uniform temperature in all parts of the
bath.
It is to minimize the danger of uneven dyeing due to this local
exhaustion that the dye-bath must be made of sufficient volume to
cover the goods well. The goods must be moved about in the bath with
the greatest freedom.
It is for the same reason, especially when the affinity between fiber
and color is very great, that the dye is added a small portion at a
time. The goods after being treated with part of the dye are lifted
out of the bath, a new portion of dye quickly added and stirred, and
the dyeing operation renewed. This is repeated until the desired shade
is obtained.
The beginner is apt to think that to get a full color requires a
concentrated dye-bath. Experience will teach him that, when the dyes
are properly chosen for his fabric, a full color is obtained better by
a longer treatment in a dilute bath, with additions of dye as
mentioned above. In this way nearly if not all of the color put into
the bath is absorbed by the cloth. This serves for economy of color,
makes observation and control of the process easier, simplifies the
problem of rinsing, and improves the quality of the dyeing. It is the
only way dyeing to shade can be accomplished.
A slow dyeing is generally more level and successful in every way. In
cases where the fiber absorbs the color greedily the dyer sometimes
puts other ingredients called "assistants" into the bath to retard
this absorption.
Frequently the craftsman does shaded dyeing, such as a scarf with
deep blue ends grading to a light blue center. The following
directions will accomplish this: Hold the scarf in the middle with one
hand, dip the ends into the dye-bath and work them thoroughly with the
other hand. Then lower the scarf into the bath very gradually without
interrupting the working. If a half hour is taken to lower the scarf
the ends will be in the bath perhaps thirty-five minutes, the center
five minutes, and besides, before the center is dyed most of the color
will have been exhausted from the bath.
4. _The Handling of the Fabric After the Dyeing._ The usual procedure
after dyeing is a thorough rinsing to remove all surplus dye and
chemicals. The importance of this will be appreciated from the
following considerations:
If not removed many chemicals which have been used as assistants,
becoming more concentrated as the goods dry, act injuriously on the
dye or the fiber. Likewise any unused color will continue to dye the
goods and of course unevenly. It is clearly essential that the rinsing
be done immediately upon removal of the goods from the bath. The
directions sometimes call for washing in soap and water after dyeing.
The excess of rinse water should be removed and the goods dried as
rapidly as possible. Usually there is no objection to wringing. A
fabric should never be allowed to hang and drain dry, as the dyeing is
liable to become uneven in streaks, especially when the dye used is
one given to run or "bleed," or in any case where the rinsing has not
been absolutely thorough. The craftsman in dyeing a small piece
frequently puts it between towels or newspapers to absorb the excess
water and then shakes it until dry. This is to be commended. The
technical dyer has suitable machinery to accomplish this work.
To dry a batik piece, where the wax forbids wringing or rough handling
in any way, spread the piece carefully on towels or newspapers, cover
with more towels or papers to remove the excess water, then shake very
gently until dry, or hang on a waxed line.
At no time during the process of dyeing should the goods be allowed to
remain in contact with other absorbent surfaces, such as boards,
paper, cloth, clothes-line, grass, etc. These are apt to absorb color
away from the goods and leave faded streaks or spots. A clothes-line
used for this purpose should be waxed to make it non-absorbent.
PATTERN DYEING
The preceding general principles have been outlined with all-over
dyeing especially in mind. We now come to the consideration of pattern
dyeing, where in order to produce a design it is necessary to dye
chosen parts of the fabric and keep the dye away from other parts. All
that has been said with reference to making all-over dyeing efficient
applies equally well to pattern dyeing. If possible, everything that
is done to make all-over dyeing successful should be done in pattern
dyeing to obtain a corresponding success.
Practically, however, we find it impossible to carry out some of the
steps. For example, in the usual block printing, we do not have the
problem of handling the fabric in a dye-bath, but rather that of
handling dye on the fabric. Here we must take special steps to get the
dye well into the fiber and secure the results obtained from the large
dye-bath in all-over dyeing.
The fabric must be prepared for pattern dyeing in the same manner as
for all-over dyeing. It is just as essential that it be clean, free of
sizing, with its fibers soft and absorbent. Attention has been called
to the pains taken by the Orientals in the preparation of their
fabrics for decoration. We must not jeopardize our success by omitting
to boil out new raw material and to clean old material.
This washing before dyeing also brings about any shrinkage that is to
occur, and of course this must be done before the design is traced on
the cloth, otherwise one could not intelligently work to dimensions.
A dyed pattern may be produced in several ways:
1. The dye is applied to the desired parts of the fabric and means
taken to set it there without it spreading to other parts. This is
known as direct coloring. Block printing and stenciling, as ordinarily
done, are examples. Calico printing is an industrial application of
the method.
2. A resist of some kind is applied to parts of the fabric to prevent
their taking the dye, after which the fabric is treated in a dye-bath.
Batik decoration and tie-dyed work both fall in this class. Stencils
and print blocks may also be used in the application of the resist.
3. A "discharge" is put on parts of previously dyed goods, which
either removes the color where it touches, or else alters the shade.
Different discharges are used according to the nature of the dye and
the goods. Some chemicals used as discharges are liable, unless
skillfully handled, to attack and tender the cloth. The method belongs
rather to the industrial world where abundant apparatus and trained
dyeing chemists are available. It is not, however, beyond the skill of
a good craftsman who has acquired some experience with dyes.
The dye for direct coloring is applied in liquid form, sometimes
thickened into a paste by use of gums, starch, etc. Often mordants or
other assisting chemicals are incorporated into the mixture. In block
printing this color mixture is brushed on the block, which is then
imprinted on the fabric in the desired place, and the color driven
into the fiber with pressure or a sharp blow. Stenciling is done by
brushing the color mixture through the open parts of the stencil, or
by blown stenciling in which a volatile color mixture is sprayed with
an atomizer.
The best method of setting the dyes in this direct coloring is that
pursued commercially in calico printing, treatment with dry steam,
_i.e._, steam applied at a temperature sufficiently high to prevent
its condensation into drops of hot water on the fabric, which would be
quite ruinous to the design. This is done successfully by Oriental
craftsmen, and it would be very desirable to have suitable apparatus
in American schools and studios.
Next best, though considerably less efficient, is the commonly
practiced method of laying the fabric between dampened cloths and
pressing with a hot iron until dry.
The resist method has an advantage in that it allows the use of a
dye-bath. The limitation of temperatures that may be used places some
restriction on the choice of dyes. Batik dyeing must be done without
melting the wax resist. But after eliminating those dyes which require
high temperatures and also those not suitable for pattern dyeing,
there still remains a good range of colors. Batik is without doubt the
most versatile of all methods of pattern dyeing.
Tie-dyed work depends upon tightly wound string or yarn to resist the
dye. It also has the advantage of the dye-bath. Though less versatile
than batik, it has a time-honored place as a method of beautiful and
charming results. The introduction of sticks over which the tying is
done, such sticks as are used by the children in stick printing, has
opened new problems with added variety and much interest.
DYES
The colors available for craft work are commonly grouped into the
following classes, which will be briefly described:
_Direct Colors._ These are so called because they are applied to all
fibers directly without the use of mordants. They are principally used
for dyeing cotton. Some dyes of this class have affinity for both
cotton and wool. Most of the package dyes sold at the local stores are
of this class. They are applied to cotton in a boiling bath and to
wool at high temperature near the boiling point. Different assistants
are used varying with the dye and the nature of the fabric.
The direct colors, being very soluble, are prone to "bleed" when the
goods are washed, but owing to this same fact it is easy to produce
level dyeing on the goods. On this same account, however, and also on
account of the high temperature required, they are not well suited for
pattern dyeing.
_Acid Colors._ These have great commercial value for dyeing wool and
sometimes silk. The best of them are quite fast to light but not to
washing. They are not suitable for cotton or linen.
_Basic Colors._ These will dye wool and silk directly and also raffia,
straw, basketry material, leather and wood. They dye cotton when
mordanted with tannic acid, and this constitutes a very large
commercial use. Basic dyes are especially strong in coloring power.
Many of them are fugitive to light. A few of the best of them,
however, when properly applied, are fast to washing and fairly fast to
light.
_Sulphur Colors._ These are used extensively on cotton, giving colors
fast to washing and to light. The dyeing is done at high temperature
in a strongly alkaline bath of sodium sulphide along with other
assistants. The colors are all dull and the range of colors is not
complete, there being a lack of reds. These dyes are not suitable for
silks.
_Vat Colors_ are so called because the method of dyeing is that of the
indigo vat. Indigo has been known for a long time, but only in recent
years have other dyes of this class been produced, until now the
series includes the entire range of colors. As a class they are the
fastest colors ever known. The best of them are so fast that the cloth
will wear out without the color changing. They are used chiefly on
cotton and linen, sometimes on silk.
Vat dyes have been very expensive and scarcely obtainable during the
war. Their future is of great interest and importance both in the
industries and to craft workers.
In addition to the dyes above mentioned there are many others the use
of which is quite complicated and technical and therefore confined to
the industries.
For a fuller discussion of dyes and their uses the reader is referred
to Pellew's "Dyes and Dyeing" (Robert McBride & Co., New York). This
is a most excellent book written for craftsmen. Like most of our
literature, the treatment of dyes is based upon pre-war conditions,
when nearly all of our colors were imported. The latest edition,
however, contains an added chapter dealing with the present
transitional state, incident to the transfer of the industry to this
side of the water and the development of great American color houses.
It may be added that the leading firms carrying school art supplies
offer dyes in suitable form especially adapted for the problems in
pattern dyeing.
Perhaps a few suggestions to the less experienced of our readers will
prove helpful. All of the good dyes manufactured today are in a very
pure form. The use of one dye alone often gives results that are crude
without any subtle beauty. It is frequently necessary to apply the
principle well known to all workers in color, that colors are softened
and beautified by small admixtures of their compliments; that one
color that is cold, or another that is hot, becomes warmed or toned by
a suitable admixture of other colors.
It may be stated that most of the beautiful dyeing is built up from
two or more colors. This is accomplished, according to the nature of
the dyes and the fabric, by mixing the colors in the same dye-bath,
or by dyeing the cloth successively in different colors. Of course the
previous condition of the fabric must be taken into account. A
bleached cotton cloth must be treated differently from a grayed one if
an equally soft effect is desired.
In the old days dyes contained impurities which often caused beautiful
grayed effects. But it is inexcusable today for anyone with knowledge
of the above principle and with elementary knowledge of dyes and
dye-baths not to get equally good results.
The inartistic work that we see so prevalent today in the realm of
dyed fabrics is due in part to ignorance and lack of appreciation of
good color and in part to the commercial race for profit. As the taste
of the people makes demand for better things the response of industry
will not be wanting.
Nor need the craftsman of today spend idle time mourning the
disappearance of vegetable colors and his necessity for using coal tar
dyes. We must remember that only the best of the vegetable dyeing has
come down to us. The proportion of poor work with vegetable dyes has
always been as large or even larger than with the present-day colors.
We are too prone to compare the ordinary home dyeing of today or the
cheaper commercial dyeing with the good pieces that have been
preserved from the past. When in justice the comparison is made of the
best with the best, the coal tar dyes not only do not suffer but they
really gain.
The coal tar dyes are like the vegetable dyes in the sense of being
organic. In many instances they are identical chemically with
corresponding dyes formerly obtained from vegetables. The one
difference, as we have indicated, is their purity. Just as our
granules of sugar have displaced the sweetening of former days; just
as our modern medicines have succeeded the herb-teas of our
grandparents, so also have come our dyes. All are achievements of
science.
Coal tar dyes have come to stay, vegetable dyes for the most part have
gone and will not return, and there is no sadness in the word. It is
rather for us to rise to the challenge that has come, to recognize our
greater heritage, and by pains, patience and intelligence in our work
to ply the art worthily.
COLOR MIXING
The following general principles of color mixing apply to dyeing, both
when colors are mixed in a dye-bath and when they are dyed one color
over another:
Red is grayed by small amounts of yellow and blue or by any color
containing both of these, as green, brown or gray.
Yellow is grayed by small amounts of red and blue or by any color
containing both of these, as purple, brown or gray.
Blue is grayed by small amounts of red and yellow, or by any color
containing both of these, as orange, brown or gray.
Red plus yellow gives orange or yellowish red or reddish yellow. These
are grayed by a small amount of blue or any color containing blue, as
green, purple, brown or gray.
Red plus blue gives purple or reddish blue or bluish red. These are
grayed by a small amount of yellow or any color containing yellow, as
orange, green, brown or gray.
Blue plus yellow gives green or bluish yellow (usually called greenish
yellow) or yellowish blue (usually called greenish blue). These are
grayed by a small amount of red or any color containing red, as
orange, purple, brown or gray.
Red plus yellow plus blue give--
(1) One of the above if any one or two of the three is present in the
small proportion necessary for graying purposes.
(2) Gray if all three are present in such proportion as to neutralize
each other. If this is perfectly accomplished we have a neutral gray,
otherwise a red gray, yellow gray, blue gray, purple gray, etc. Gray
intensified becomes black, and there are modified blacks, as blue
black, green black, etc. In making up a gray or black, beginners
usually err in taking too large a proportion of yellow, and perhaps
also of red.
(3) Brown if the three are present within certain other ranges of
proportion. Browns may be classified as yellow browns, red browns,
blue browns, green browns, purple browns, etc.
There are all gradations between neutral gray and the browns; between
the browns and the secondary colors, orange, green and purple; between
the secondary colors and the primary colors, red, yellow and blue.
In the practical handling of dyes, in order to get the entire range of
colors from the primary colors, it is necessary that the red, yellow
and blue dyes chosen be pure and luminous in color quality.
Fortunately, there are such dyes.
There are, however, other valuable dyes that do not have this purity
of color. For example, there are yellows containing considerable red
or brown, reds containing yellow or blue, blues containing red, etc.
Then there are dyes that are green, brown, purple and black. All of
these have limitations when used in compounding colors. Neither a
yellow inclined to the brown, nor a red containing blue, can be used
to form a luminous orange. Likewise the compounding of a vivid blue
green, or reseda green, forbids either the yellow or the blue
containing any appreciable admixture of red.
All of these dyes find great use in the industries, and all of them,
within their limitations, are valuable for color mixing. Having
acquired a working knowledge of red, yellow and blue dyes, it will be
found of practical benefit to include some of the others. An
experienced craftsman works with a small range of colors chosen for
his particular purpose.
Dyes differ in coloring power, even different specimens of the same
dye, so that it is not possible to give quantitative formulas for
certain colors bearing popular names. It will be helpful to discuss a
few of them.
Olive green may be made by adding to blue-green either red or
preferably yellow brown. This addition should be made a little at a
time with frequent tests, a suggestion applicable to all color mixing.
Tan is obtained by mixing yellow and yellow brown. An added tinge of
blue or green gives pongee.
Gold contains much yellow with certain smaller amounts of red and
blue. But it might be difficult to control the addition of these
colors, so it is better to start with much yellow and add a little at
a time orange and blue green.
For burnt orange add yellow brown to orange.
For turquoise add to blue a little yellow, or preferably blue green.
For old rose add to dilute red a tinge of blue or preferably purple.
Taupe is a gray thrown off, usually with purple, but sometimes with
red or yellow or blue.
Salmon is formed by adding to yellow some orange and a tinge of brown.
Any dyeing over old color must be considered as a mixing of the new
color with the old, which manner of thinking will help in choosing the
dye necessary for a desired effect. For example, a green cloth is to
be dyed black. There should be two dyeings, the first a red to
neutralize the green, the second a black to intensify the neutrality.
Likewise a red cloth becomes black by dyeing first green and then
black.
Over a light yellow purple may be dyed, the result will be a grayed
purple. Over a strong yellow much purple will be required and the
result will be a very much grayed purple approaching if not becoming a
purple black.
In batik decoration by successive dyeings the craftsman is constantly
mixing the new dye with that already in the fiber. Having once
introduced an intensity of any primary color, yellow, red or blue, he
must thereafter, unless he removes this color, complete his pattern by
producing secondary and tertiary colors.
[Illustration: {BATIK DESIGN} {p. 53}]