necessary to repeat the dyeing several times in order to obtain the proper
depth of shade working in the cold. Only the brush method can be used in
applying the Aniline Black dye to furs, on account of the strong acidity
of the dye mixture, which would ruin the leather, if the dyeing were done
in a bath. Indeed, great care must be exercised even by the brush method
to avoid too great penetration of the dye liquid, otherwise the roots
of the hair will be attacked, and the leather may be “burned” from the
hair side. Furs dyed with Aniline Black are frequently after-dyed by the
dip-process with logwood or some other similar dye, in order to add to
the brilliancy of the dyeing. Combined with intensity of color, Aniline
Black on furs is the only dye which will also give fast, lustrous shades,
and leave the hair soft and smooth.

There are several methods of applying Aniline Black on furs, the most
important being

  1. One-bath Aniline Black
  2. Oxidation Aniline Black
  3. Diphenyl Black
  4. Aniline Black by Green’s Process

1. _One-bath Aniline Black_

A typical formula for this method is the following given by Beltzer:

  Aniline salt            10 kg.
  Sodium chlorate        1.5 kg.
  Copper sulphate        0.7 kg.
  Vanadate of ammonia     10 gr.

All these substances are dissolved hot in 50 liters of water, and allowed
to cool, forming solution A. Aniline salt is aniline oil which has been
neutralized with the exact quantity of hydrochloric acid to form the
hydrochloride. It forms white or greyish crystalline lumps very easily
soluble in water. The sodium chlorate is the oxidizing agent, and the
copper sulphate and the vanadate of ammonia are the oxygen carriers.

15 kg. of sodium bichromate are also dissolved in 50 liters of water,
forming solution B. The bichromate is also an oxidizing agent and serves
to complete the oxidation of the aniline to the black.

Immediately before using, solutions A and B are mixed together, both being
cool. In general practise it is customary to mix only small quantities
at a time, as a considerable precipitate forms when the whole batch
is mixed at once, the precipitate being so much waste dye substance.
Usually a liter of A and a liter of B are mixed at a time, and the furs
brushed with the mixture. The brushing must be varied according as the
hair is hard and stiff, or soft and tender. The hair must be thoroughly
impregnated in all directions, and the penetration must not be too deep
to affect the leather. With experience and dexterity satisfactory results
can easily be achieved. After the skins have been properly treated, they
are dried at a temperature of about 35 degrees centigrade. When dry, they
are returned to the dye bench, where they receive another application
of the dye mixture, and are again dried. This operation may be repeated
as often as six or seven times before a sufficiently intense black is
obtained. Another way of producing the desired depth of shade with fewer
applications is by using more concentrated dye mixtures. Each method
has its disadvantages, the greater number of brushings requiring the
expenditure of more time and labor, and the greater concentration of
the bath resulting in a considerable loss of dye substance due to the
formation of a large precipitate when the two solutions are mixed, and
moreover, not all furs can be treated with concentrated mixtures. The best
results with this method usually require the application of six coats of
a mixture of moderate concentration.

2. _Oxidation Aniline Black_

In order to overcome the difficulty of employing very concentrated dye
mixtures, or of making many applications of the dye, a method was devised
whereby the two solutions of the previous process, instead of being mixed
together, are applied successively to the hair of the furs, the following
formula, also by Beltzer, being an example:

  Aniline oil                     10 liters
  Nitric acid 36° Beaumé, or
  Hydrochloric acid 22° Beaumé    20 liters
  Cold water                      20 liters

This is solution A, and is merely a solution of aniline hydrochloride,
or nitrate, depending on which acid has been used. Nitric acid, although
more costly than the hydrochloric acid, is to be preferred, because it
is an oxidizing acid, and so assists in the oxidation of the aniline, and
besides, has a more beneficial effect on the hair than the hydrochloric,
in the matter of softness and luster.

  Sodium chlorate          4 kg.
  Copper sulphate          1 kg.
  Vanadate of ammonia     10 gr.
  Water                   50 liters

This is solution B, containing the oxidizing agent, and the oxygen
carriers. Just before using, equal quantities of A and B are mixed, and
the skins brushed with the mixture. The skins are then dried at 35–45°
centigrade, at which temperature the color begins to develop. When almost,
but not entirely dried, the skins are subjected to the action of warm
vapor, which is allowed to enter the drying chamber, so as to keep the
temperature about 40° centigrade, the color developing better in this
way. This operation may be repeated, or the skins are directly treated
with a solution of 25 kg. of sodium bichromate in 100 liters of water,
to complete the oxidation. The moist skins are exposed to the air for a
time, and then dried at 35° C.

This method of dyeing has several advantages over the One-bath Aniline
Black. It requires fewer brushings, and enables the complete utilization
of the dye solutions without loss. With three applications of the dye
mixture by the Oxidation process, as deep and intense a black can be
obtained as with six brushings by the One-bath method. The dyeings, too,
are nearly, but not fully as brilliant and even as in the latter case.
The greater the number of coats of dye that are applied the more regular
will the dyeing be.

3. _Diphenyl Black_

In 1902, the Farbwerke Hoechst, a large German producer of coal tar
intermediates and dyes, invented an Aniline Black process to which they
gave the name Diphenyl Black. The chief departure from the previous
Aniline Black methods was the replacing of part of the aniline oil of the
dye mixture by Diphenyl Black Base I, which is para-aminodiphenylamine.
This base has the property of being oxidized to Aniline Black, just like
aniline oil, and the advantage claimed for the Diphenyl Black is that it
produces an absolutely ungreenable black. The method of application is
practically the same as for the other Aniline Black processes, chlorates
being used as the oxidizing agents, in the presence of oxygen carriers
such as salts of copper and vanadium. The use of bichromates is dispensed
with. On account of the comparatively high cost of the Diphenyl Black
Base I, this method has not found very extensive application, especially
as highly satisfactory ungreenable blacks can now be produced by other
methods.

4. _Aniline Black by Green’s Process_

In 1907, Green, who has done much work in the direction of elucidating the
character of the Aniline Black process, obtained a patent for a method
of applying Aniline Black in a manner which was different from all the
previously known formulas. The invention created great interest, and
although in its original form it did not find a wide application, many of
the methods used at the present time are in one way or another derived
from the idea of Green. A resumé of the patent will therefore be given
here: “The invention relates to the production of an Aniline Black, the
new process differing from all other known processes by the fact that
the oxidation of aniline is effected solely or mainly by the oxygen of
air. The possibility of dispensing with an oxidizing agent depends on the
discovery that the addition of a small quantity of a para-diamine, or of
a para-amido-phenol to a mixture containing aniline and a suitable oxygen
carrier, such as a salt of copper, greatly accelerates the oxidation of
the aniline by the atmospheric oxygen. Further, whereas in the ordinary
processes of Aniline Black, the quantity of mineral acid employed cannot
be materially reduced below the proportion of one equivalent to one
equivalent of the base, under the new conditions the mineral acid may
be wholly or partially replaced by an organic acid such as formic acid,
without the quality of the black being materially affected. As suitable
oxygen carriers the chlorides of copper have been found to give the best
results, it being preferrable to use the copper in the form of a cuprous
salt. This is effected by adding to the dye mixture cupric chloride,
together with a sulphite or bisulphite in sufficient quantity to reduce
the cupric salt to the cuprous state, and a sufficient quantity of a
soluble chloride to keep the cuprous chloride in solution. Among the
compounds suitable for the production of this black in conjunction with
aniline are, para-phenylene-diamine, dimethyl-para-phenylene-diamine,
para-amido-diphenylamine, para-amido-phenol, etc.”

This method may be used alone as the other Aniline Blacks, or the dyed
skins may be after-dyed in a bath containing a logwood dye, or it may be
used in conjunction with mineral dyes, or with the Oxidation Colors (see
next chapter). A typical formula for the black by Green’s process is the
following:

  Para-amido-phenol            0.5 kg.
  Aniline oil                   10 liters
  Hydrochloric acid 22° Bé.     10 liters
  Acetic acid 40%                5 liters
  Cold water                    25 liters

This is solution A. Solution B is prepared by dissolving

  Copper sulphate       2 kg.
  Salammoniac          10 kg.
  Cold water           50 liters

A and B are mixed, and the mixture applied to the hair of the furs several
times, drying each time at 35°–40° C. After three coats of dye have
been applied, a pretty and fairly intense black shade is obtained, which
is developed further by treating with a solution of 25 grams of sodium
bichromate per liter of water. The skins are then allowed to dry in air,
and then if desired, an after-dyeing is made with some other dye.

On account of its extreme fastness, Aniline Black, produced by any of
the methods outlined above, has attained a justifiable popularity for
the dyeing of furs, in spite of the necessity of using the more or less
cumbersome brush method of applying the dye. Very recently there was
issued to a German company a patent in which is described a method whereby
furs can be dyed with Aniline Black by the dip process. An abstract of
the patent (D. R. P. 33402) is as follows: “As is known, aniline salt,
and similar salts, together with oxidizing agents like bichromates,
chlorates, etc., cannot be used for dyeing furs by the dip process,
because the strongly dissociated mineral acid is injurious to the leather.
The dissociation of the acid can be reduced by adding neutral salts, like
common salt, or Glauber’s salt, so that good results can be obtained by
dyeing in a bath of the dye mixture, the leather retaining its softness.”

Thus far there have been no reports of the successful practical
application of this patent, so its value cannot be discussed. It is
extremely doubtful, however, that furs will ever be dyed in the dyebath
with the present type of Aniline Black formulas, no matter what substances
are added to prevent the leather from being affected.

CHAPTER XV

FUR DYEING

OXIDATION COLORS

The year 1888 may be considered the beginning of a new era in the
history of fur dyeing; the commencement of a period which was to see
the time-honored, traditional methods of the masters of the art give way
to newer methods of an entirely different character; and moreover, the
initiation of an age when science with its basis of fact and logic, was
to undertake the rationalization of an industry which had hitherto worked
upon a more or less irrational, empirical and uncertain comprehension
of the fundamental principles involved. It was not the work of a single
day, or even of a year which brought about the virtual revolution in the
dyeing of furs, but the result of long, patient, systematic effort. About
this time, the German coal tar industry was attaining its real stride
along the path of progress and achievement, and had already succeeded in
reaching, to an appreciable degree at any rate, most users of coloring
matters, with the consequence that the natural dyes, with their time and
labor-consuming processes of application were gradually being superseded
by the new synthetic dyestuffs which could be simply and quickly applied.
It was now the turn of the fur dyeing industry to receive the attention of
the scientists and technologists responsible for the growth of the coal
tar dye industry, and so there appeared in the above-mentioned year, the
following patents, taken out by a German chemist named Erdmann:

D. R. P. 47349

A Process for Dyeing Hair and Feathers

If white hair or feathers are soaked in an aqueous or alcoholic solution
of para-phenylene-diamine, and then exposed to the slow oxidation of
the air, or are treated in a second solution with some oxidizing agent,
then the hair or feathers will be dyed. According to the oxidizing agent
chosen, and the concentration of the solution used, the color obtained
will be light or dark, varying from the palest blond to the deepest
blue-black. Particularly suitable as oxidizing substances are ferric
chloride, permanganates, chlorates, hypochlorites, bichromates, and
hydrogen peroxide. The dyeings are fast, that is, they do not come off,
and the color cannot be removed by washing. Following examples may serve
to make the process clear:

20 grams pure para-phenylene-diamine and 14 grams caustic soda are
dissolved in a liter of water. The hair, previously degreased, is soaked
thoroughly in this solution, and while moist is entered into a three per
cent solution of peroxide of hydrogen. The action is not instantaneous,
but after a day, the hair is dyed a dark shade; by repetition of these
operations a blue-black is obtained.

The para-phenylene-diamine can be replaced in this process by other
similar bases, such as dimethyl-para-phenylene-diamine, as well as the
naphthylene-diamines. Since the substances which can be applied by this
process are uninjurious, the method described can be used to dye human
hair on the head or beard, and so seems suited to replace for the dyeing
of hair, the metallic salts and various pyrogallic solutions which are on
the market, and which are harmful to the health.

D. R. P. 51073 Supplement to 47349; Process for Dyeing Hair

This patent was an extension of the original patent to include certain oxy
and amido-oxy compounds, the method being essentially the same otherwise
as in the original patent. An illustration of the process is as follows:

73 grams para-amido phenol hydrochloride are dissolved with 40 grams
caustic soda in a liter of water. The solution dyes hair a golden-yellow,
which on subsequent treatment with a solution of ferric chloride turns to
a red-brown.

In these two patents is to be found the basis of the modern fur dyes
and fur dyeing methods. It is interesting to note that furs were not
mentioned at all in connection with the process, which was intended
mainly for dyeing hair, especially on the human head. It was only several
years later that the value of the method for dyeing furs was realized.
So about 1894, the Aktien Gesellschaft für Anilinfabrikation put upon
the market three fur dyes under the trade name Ursol, Ursol D, giving
dark-brown to black shades; Ursol P, giving red-brown colors; and Ursol
C, giving a yellowish-brown shade. Pyrogallic acid had been previously
used as a hair dye, and also to a slight extent as a fur dye, so it was
used in conjunction with the Ursol dyes for shading purposes. The new fur
dyes were not dyes in the ordinarily accepted sense of the term. They
were really coal-tar intermediates, substances similar in character to
aniline, and their dyeing property depended on the fact that they could
be oxidized either by atmospheric oxygen, or by means of oxidizing agents,
forming colored insoluble products. When the oxidation of the intermediate
was caused to take place on the hair the colored product formed on and
in the hair fibre, and remained fast. The reactions bringing about the
conversion of the intermediate to the colored insoluble compound are quite
analogous to those of the Aniline Black process, though possibly not so
complicated, with the important difference, however, that, while in the
production of Aniline Black acid is essential, in the present instance the
oxidation can be carried on in neutral or even alkaline medium. On account
of the character of the method used in applying the new fur dyes, the
name Oxidation Colors has been given to them. Strictly speaking, Aniline
Black is also an Oxidation dye, but it is usually considered in a class
by itself. The methods used at first in the application of the Ursol dyes
to furs followed closely the process as described in the patents. The furs
were first killed, usually by brushing on a lime mixture, drying, and then
beating out the dust. This operation was repeated, if necessary. Then a
solution of the desired dye, mixed with an equal volume of 3% peroxide of
hydrogen was brushed on and the fur allowed to lie exposed to the air. The
dyeing could also be done by the dip process, less concentrated solutions
being used. By varying the concentration of the solution, and prolonging
or shortening the time of action, the shades could be varied from very
light to very dark, and by combining two or more of the Oxidation Colors,
many different color effects could be produced. Soon other fur dyes were
developed and put on the market; for example, Ursol DB, giving blue to
blue-black shades, and Ursol 2G, yielding yellowish tones suitable for
mixing with the other colors. Ursol C was discarded shortly after its
introduction. The dyeings obtained with the Oxidation Colors seemed to be
very fast, resisting successfully the action of cold or hot water, or even
hot soap solution. Moreover, a dyed hair examined under the microscope
appeared to be colored through the epidermis to the medulla, and no
individual particles of dye could be discerned.

The new fur dyes had many evident advantages over the coloring matters
in general use at the time. The simplicity of the dyeing operations,
the short duration of the process, the great tinctorial power of the
new products, were facts which strongly recommended themselves to the
progressive fur dyer. The cost of the dyes was higher than that of the
vegetable dyes, but this consideration was largely overbalanced by the
saving in time and labor in using them. And yet, the Ursol dyes found
only a comparatively small market. The majority of fur dyers, always
conservative and reluctant to turn from the traditional ways of the
industry were skeptical of, and even hostile towards the new dyes and
the new methods of dyeing. In a sense, this opposition was justifiable.
It was not an easy task to relinquish all at once methods which had
been successfully applied for generations back, and with which they
were thoroughly experienced, in favor of processes which were radically
different, and with which they had no experience at all. But some
enterprising spirits among the fur dyers undertook to try out the new
products and it was not long before the skeptics had good cause for
condemning the work and achievements of the chemists as far as fur dyeing
was concerned. The new type of dyes did possess some of the advantages
claimed for them, but they also possessed many highly objectionable
features, which had never been manifest with the vegetable dyes. First
of all, the dyeings were not so fast as had at first appeared, for the
color came off the hair when the furs were rubbed, brushed or beaten.
Then it was observed that after a short time some of the dyeings changed
color, and at the same time the hair lost its gloss and became brittle.
The condition of the leather after dyeing was anything but satisfactory.
Most serious of all, however, was the appearance among the workers in
the dyeing establishments, and also among the furriers who worked with
the dyed skins, of certain pathological conditions which had hitherto
been unknown. Various skin diseases, eczemas, inflammation of the
eyes, asthmatic affections and intestinal irritations were some of the
afflictions which were directly attributable to the use of fur dyes of
the Ursol type. Medical science was at a loss to know how to treat these
ailments, because their nature was not understood.

Here indeed, were obstacles threatening to destroy all the hopes which
the discovery of the new class of dyes had aroused, and to check at the
outset the possibility of rational progress in the fur dyeing industry.
But the men of science were not content to let the matter drop thus.
Difficult problems had been solved before, and surely there must be
some way of overcoming the objections and deleterious features of a
system of fur dyeing which had so much potential merit. Where hindrances
sprang up in the path of progress, it was the duty of the chemist to
remove them, and when difficulties arose, it was up to him to resolve
them, as far as was humanly possible. So the chemists who had been
responsible for the introduction of the Oxidation Colors set themselves
to the task of eliminating the undesirable or injurious qualities. It
was many years before the results of painstaking effort and persistent
study cleared up the causes of all the objectionable aspects of the fur
dyes, and suggested means of overcoming them satisfactorily. The work
had been directed to the improvement of the dyes and of the methods of
dyeing with them. Purer intermediates were produced, and more easily
soluble ones, so that there would be no possibility of ultra-microscopic
particles of the dye being deposited on the surface of the hair from the
dye solution, instead of being taken up within the hair fibre. It was
this superficial deposition of minute crystals of the dye or of the only
partially oxidized intermediate, on the hair, crystals so fine as to be
invisible in the ordinary high-power microscope, which caused the color
to come off when the furs were brushed or beaten, giving rise to a dust
which was frequently very injurious to the health. Then, mordants were
adopted to help fix the dyes, compounds of copper, iron, and chromium
being used as formerly with the vegetable dyes, and the range of shades
was also increased thereby. Certain of the Oxidation Colors had a tendency
to sublime off the hair, so the dyed hair was chemically after-treated
in such cases to prevent this. The causes of the pathological aspects of
dyeing with the Oxidation fur dyes were not so readily disposed of. But
the adoption of devices to prevent the formation and circulation of dust
during the handling of the dye, the employment of adequate protection
against contact with the dye or its solutions, the use of the most dilute
solutions possible in dyeing, the thorough washing of the dyed skins to
remove any excess of the coloring matter, the prevention of dust formation
in the drying of the skins, and the rigid observance of, and adherence to
hygienic laws, were all factors in the elimination of the health-impairing
phases of dyeing with the Oxidation Colors.

It was only after all these improvements had been accomplished that the
fur dye intermediates began to acquire a degree of popularity among fur
dyers, and strange as it may seem, there was a more ready market for
these dyes in America, than in Germany where they were manufactured. Other
manufacturers of coal-tar intermediates also began to produce fur dyes,
and so, in addition to the Ursols, there were the Nako brand, the Furrol
brand, the Furrein brand, and one or two others. New dyes were invented,
until the whole range of colors suitable for fur dyeing had been produced.
The black dye, however, presented some difficulty. A black dye which would
rival logwood blacks could not be attained. Ursol DB in conjunction with
Ursol D was being used to produce bluish-blacks, but the dyeings were not
fast, turning reddish after a time. In 1909, a patent was taken out for
a dye mixture, which was made up like the DB brand, but instead of using
toluylene diamine with para-phenylene-diamine, the new dye was made up of
a methoxy, or ethoxy-diamine with para-phenylene-diamine, and it yielded
brilliant bluish-blacks, which were fast, and which very nearly approached
the logwood black in luster, intensity, and bloom. For some purposes,
however, the production of a black color is still dependent on the use of
the logwood dye.

When the Great War cut off to a large degree the importation of skins
dyed in Europe, the American fur dyeing industry developed tremendously,
and in a comparatively short time was able satisfactorily to accomplish
in the way of dyeing furs, what had taken foreign dyers a much longer
period to attain. It had been previously considered that furs could be
dyed properly only by European fur dyers, but the achievements in this
direction by Americans fully dispelled this belief. But the success of
the fur dyers in America might not have been so marked or rapid, had it
not been for the work of the American chemists. The war had also shut off
the supply of German dyes, upon which the dyeing industries of America
had formerly been dependent, so enterprising chemists in this country
undertook to fill the need, and in a surprisingly short time, American fur
dyes, in every respect the equal of the foreign product were offered to
the American fur dyers, and at the present time, the requirements of the
fur dyeing industry in this country are being adequately met by domestic
producers. Among the brands on the market are the Rodol, Furamine,
Furol, and several others. The Oxidation Colors are now being offered
in a high state of purity, and easily soluble, free from any poisonous
constituents, and there is absolutely no reason for the appearance of
any pathological conditions among workers on dyed furs, or users of such
furs, provided the necessary precautions have been taken in the dyeing
process. The occurrence of any affection which can be traced to dyed fur,
cannot possibly be due to the dye itself, but to gross carelessness and
negligence in dyeing, and in any such event, the dyer responsible should
be brought to account.

In order to get a better understanding of the nature and action of the
Oxidation Colors, a typical one will be studied in some detail. The most
important one in this class is para-phenylene-diamine, usually designated
by the letter D in all commercial brands of this fur dye, while its
chemical formula is represented as C₆H₄(NH₂)₂. When pure it occurs in
colorless, crystalline lumps, which rapidly turn brown when exposed to
the air; the technical product of commerce is of a dark-brown color.
It dissolves readily in hot water when pure, and also in acids. At one
time the hydrochloride was used instead of the free base, on account
of its greater solubility, but now a base is made which is sufficiently
pure to be very soluble in water. There are several methods of preparing
para-phenylene-diamine: first, by the reduction of amido-azobenzol,
the product obtained in this way always containing a slight amount of
aniline, which reduces the solubility, and also gives rise to poisonous
oxidation products during the dyeing process; second, by the reduction
of paranitraniline, the quality and solubility of the product in this
case depending on the purity of the starting material; and third, by the
treatment of para-dichloro-benzol with ammonia under pressure, the best
product being obtained by this method. The crude para-phenylene-diamine,
made by any of the above processes, is generally distilled in vacuo, the
refined base being obtained as lumps with a crystalline fracture.

The first step in the oxidation of the para-phenylene-diamine is the
formation of quinone di-imine, NH:C₆H₄:NH. This is a very unstable
compound in the free state, and even in aqueous solution it decomposes
within a comparatively short time, or combines with itself to form a more
stable substance. Quinone di-imine has a very sharp, penetrating odor, and
produces violent local irritations wherever it comes in contact with the
mucous membrane. If a small quantity of para-phenylene-diamine is absorbed
into the human body, by breathing the dust, or otherwise, the formation
of quinone di-imine takes place internally with consequent irritation of
the mucous lining throughout the body. The various pathological conditions
mentioned before may be ascribed to irritation caused by quinone
di-imine. In any dyeing process where there is a possibility of the
formation of quinone di-imine, as is the case with most dyes containing
para-phenylene-diamine, special precautions must be taken by the workers
in handling the dye or coming in contact with its solutions, and no one
who is particularly sensitive to irritation should be permitted to work
in a place where such dyes are used.

The next step in the oxidation of the para-phenylene-diamine is the
formation of what is called Bandrowski’s base. Three parts of the quinone
di-imine combine with themselves, forming a substance of a brown-black
color, which was formerly regarded as the final oxidation product. The
formula of Bandrowski’s base is represented by the following chemical
hieroglyphics:

  (NH₂)₂.C₆H₃.N:C₆H₄:N.C₆H₃(NH₂)₂.

Further investigation has shown that the oxidation proceeds beyond this
stage with the formation of a compound of what is known as the azine type,
which is depicted by the chemist as

             NH      NH
  (NH₂).C₆H₃<  >C₆H₂<  >C₆H₃.NH₂.
             NH      NH

It is by no means certain that this substance is the true coloring matter
obtained by the oxidation of para-phenylene-diamine, for the reactions
may continue still farther, producing even more complicated oxidation
products. Scientific research and study has not as yet gone beyond this
stage.

The reactions of the other dyes of the Oxidation type are quite similar to
those of para-phenylene-diamine, some being simpler, and others being even
more complex. The presence of certain chemical groups in the intermediate,
or the relative position of such groups are factors responsible for the
variations in shade.

With the various mordants, the Oxidation Colors give different shades, and
a great range of colors can be produced either by combining mordants, or
combining dyes, or both. The following tables illustrate the shades formed
with the customary mordants.

  =========================================================================
           |    CHROME     |     COPPER     |     IRON     |    DIRECT
  ---------+---------------+----------------+--------------+---------------
  Ursol D  | brown black   | coal black     | coal black   | dark brown to
           |               |                |              |   brown black
  Ursol P  | dull red brown| dull dark brown| grey brown   | light brown
  Ursol 2G | yellow brown  | dull yellow    | yellow brown | dull yellow
           |               |   brown        |              |
  Ursol A  |    ...        |     ...        | blue black   | blue to blue-
           |               |                |              |   black
  Ursol 4G | light brown   | medium brown   | yellow       | pure yellow
  Ursol 4R | orange brown  | light yellow   | red brown    | orange red
           |               |   brown        |              |
  Ursol    |               |                |              |
    Grey B | greenish grey | greenish grey  | mouse grey   |     ...
  Ursol    |               |                |              |
    Grey R | brownish grey | brownish grey  | reddish grey |     ...
  ---------+---------------+----------------+--------------+---------------

Fur dyes of American make being equal in every way to the German product,
show the same color reactions with the various mordants. The following
table shows the shades produced with the same mordants as above:

  =========================================================================
           |    CHROME     |    COPPER     |     IRON      |     DIRECT
  ---------+---------------+---------------+---------------+---------------
  Rodol D  | brown black   | coal black    | coal black    | brownish black
  Rodol P  | red brown     | dark brown    | grey brown    | light brown
  Rodol 2G | yellow brown  | yellow brown  | yellow brown  | dull yellow
  Rodol 4G | light brown   | light brown   | reddish brown | pure yellow
  Rodol A  |     ...       | blue black    |     ...       | blue black
  Rodol    |               |               |               |
    Grey B | greenish grey | greenish grey | mouse grey    |     ...
  Rodol    |               |               |               |
    Grey R | greenish grey | brownish grey | mouse grey    |     ...
  ---------+---------------+---------------+---------------+---------------

All these shades are produced by dyeing in a bath containing a _neutral_
solution of the dye. Sometimes the dye comes in the form of a salt of
a mineral acid, like hydrochloric or sulphuric acid, in which case a
sufficient amount of an alkali, usually ammonia, is added to liberate
the free base. According to the Cassella Co., German manufacturers of the
Furrol brand of fur dyes, the dyeing can also be carried on in slightly
alkaline or in slightly acid solution, a different series of shades being
obtained in each instance. Ammonia is used to render the bath alkaline,
and formic acid to make it acid. The most customary practise, however, is
to use neutral solutions of the dyes.

For preparing the mordant solutions much smaller quantities of the
metallic compounds are used than in the case of the vegetable dyes. With
chrome mordants cream of tartar is always employed as an assistant, and
occasionally also with copper and with iron mordants. With copper, and
also with iron mordants no addition is made at all, or sometimes a small
quantity of acetic acid is added. The temperature of the mordant solution
is kept about 30° C., and the duration of the mordanting varies from 2–24
hours according to the depth of shade desired. The concentration of the
solution may also be varied, it sometimes being just as well to use a
strong mordant solution and less duration of mordanting. Chrome may be
combined with copper, and iron may be combined with copper, but chrome
and iron do not go together as mordants. Some typical average mordanting
formulas are as follows:

         Chrome mordant.
  Bichromate of soda    2.5 gms.
  Cream of tartar       1.5 gms.
  Water                   1 liter

         Copper mordant.
  Copper sulphate         2 gms.
  (Acetic acid 50%        2 gms.)
  Water                   1 liter

          Iron mordant.
  Ferrous sulphate        2 gms.
  (Acetic acid 50%        2 gms.)
  Water                   1 liter

or,

  Iron pyrolignite 30%   10 gms.
  Water                   1 liter

      Chrome-copper mordant.
  Bichromate of soda      2 gms.
  Copper sulphate      0.25 gms.
  Cream of tartar       1.0 gms.
  Water                   1 liter

       Copper-iron mordant.
  Copper sulphate         2 gms.
  Ferrous sulphate        2 gms.
  (Acetic acid 50%        2 gms.)
  Water                   1 liter

The killed skins are immersed in the mordanting solution, and allowed
to remain the required length of time. They are then thoroughly rinsed
to remove any excess of the mordant, and are hydro-extracted. Under no
circumstances should mordanted skins be permitted to dry, for they would
be unfit for use again.

The dyebath is next prepared by dissolving the necessary quantity of the
dye, varying from 0.1 gm. to 10 gms. per liter. Then if the solution must
be neutralized, the ammonia is added and the temperature of the bath is
brought to 30–35° C. by the addition of cold water. This temperature is
maintained throughout the dyeing operation. To the solution is added the
oxidizing agent. Ordinary commercial peroxide of hydrogen containing 3%
by weight is the usual oxidizer, although perborates have been suggested.
15–20 parts of peroxide of hydrogen for every part of dye are added, and
the dye solution brought to the proper dilution. As soon as the dyebath is
ready, the skins are entered, and worked for a short time to effect even
penetration. They are then left in the dyebath for 2–12 hours or longer
according to the depth of shade. After being satisfactorily dyed, the furs
are rinsed thoroughly, hydro-extracted and dried and finished. Where the
dye is to be applied by the brush to the tips of the hair, stronger dye
solutions are used, the brushed skins being placed hair together and let
lie for about 6 hours in order to permit the color to develop, after which
the furs are dried and drum-cleaned.

Some shades, particularly black, have a tendency to rub off slightly. In
order to overcome this, the dyed furs, after rinsing, are treated with a
cold solution of 1/2 part of copper sulphate per 1000 parts of water, for
3–4 hours, then without rinsing, hydro-extracted and dried. Furs which
have been tipped are brushed with a 1–2% solution of copper sulphate and
dried. Care must be taken in this after-treatment, for the use of too
strong a solution of copper sulphate, or too prolonged action of such a
solution will materially alter the shade of the dyed fur.

A few typical formulas will serve to illustrate the general methods of
employing the Oxidation Colors:

_Brown Sable Imitation on Unsheared Rabbit_

The skins are killed with soda, soured, and washed, then mordanted with

  Bichromate of soda      2 grams
  Copper sulphate       .25 grams
  Cream of tartar         1 gram
  Water                   1 liter

for 24 hours. Then washed, and dyed for 24 hours with

  Fur Brown 2G[3]         3 grams
  Hydrogen peroxide      45 grams
  Water                   1 liter

Wash and dry the skins, then brush the tips with

  Fur Brown D[3]         20 grams
  Hydrogen peroxide     400 grams
  Water                   1 liter

  [3] Inasmuch as most manufacturers use the same letters to designate
      the various dyes, any equivalent brand of fur dye may be used in
      place of those here mentioned.

_Black on Sheared Muskrat_

The skins are killed with soda, soured, and washed, then chrome mordanted
for 6 hours. Then they are dyed for 6 hours with

  Rodol P               1.5 grams
  Pyrogallic acid        .7 grams
  Ammonia               2.0 grams
  Hydrogen peroxide      45 grams
  Water                   1 liter

The dyed skins are washed and dried, then tipped with

  Rodol D                20 grams
  Rodol DB                2 grams
  Hydrogen peroxide     450 grams
  Water                   1 liter

_Brown on Thibet Sheep Skin_

The killed skins are mordanted for 6 hours with a chrome mordant, then
dyed for 6 hours with

  Ursol P                 1 gram
  Pyrogallic acid         1 gram
  Ammonia                 2 grams
  Hydrogen peroxide      40 grams
  Water                   1 liter

It is also possible to combine dyeings with the Oxidation Colors with
Vegetable dyeings, or with Aniline Black. For example, if it be desired
to produce an imitation skunk on a raccoon, and an exceptionally fast and
intense and lustrous black on the tips of the hair, the skins are dyed
in the bath with the Oxidation dyes, and the tips of the hair are brushed
with a mixture such as described under Vegetable Colors for the production
of French seal, as follows:

_Imitation Skunk on Raccoon_

The skins are killed with caustic soda, soured and washed, then mordanted
with an iron-copper mordant as described, and then dyed with

  Fur Grey R              3 grams
  Ammonia                 2 grams
  Peroxide of hydrogen   45 grams
  Water                   1 liter

After washing and drying, the dyed skins are brushed over with a mixture
such as used for dyeing French seal with Vegetable Colors.

In a similar manner, the Oxidation Colors may be used to give a base color
to furs dyed by the Aniline Black process.

It is apparent from these few illustrations that a great variety of shades
can be produced, and the dyeing of imitations of the better class of furs
on cheaper skins is a comparatively simple matter, after an understanding
of the nature of the dyes has been obtained, and a certain amount of skill
acquired in working with these dyes.

CHAPTER XVI

FUR DYEING

COAL TAR DYES

In addition to the Aniline Blacks and the Oxidation Colors already
discussed there are certain of the synthetic coal tar dyes such as are
generally used in the dyeing of textiles, which can also be applied on
furs. There are several classes of these dyes, varying somewhat in their
nature, and consequently in their manner of application; in the main they
produce bright shades, such as are but seldom used on furs, yet which may
occasionally serve for the production of novel effects. Basic, acid and
chrome colors are the types which can be employed.

Basic colors possess great fullness and tinctorial strength, but have a
tendency to rub off, and the tips of the hair take a darker shade with
these dyes than the rest of the hair. The addition of acetic acid and
Glauber’s salt to the dyebath will result in a more uniform dyeing. On
account of the comparatively poor fastness to rubbing and washing, basic
dyes are used only for dyeing furs which are intended for cheap carpet
rugs, such as sheep and goat. They may also find use in the production
of light fancy shades on other white furs. The procedure is usually as
follows: The furs are killed in the customary manner with soap and soda
or ammonia, or if this is insufficient, with milk of lime. A soap-bath is
then prepared containing 2.5–6 grams of olive-oil soap per liter of water.
The temperature of the bath is brought to 40° C. To this is added the
solution of the dyestuffs, prepared by mixing the required color or colors
with a little acetic acid to a paste, and then pouring boiling water on
the mixture until dissolved. Undissolved particles or foreign matter are
removed by passing this solution through a cotton cloth or sieve, and
the clear solution then mixed with the soap-bath. The well-washed skins
are then entered into the dyebath and immersed for about half an hour,
or until the desired depth of shade is obtained. They are then removed,
pressed or hydro-extracted and dried. For the production of light shades,
the following dyes may be used:

For cream, light sulphur-yellow, maize, salmon, etc.
  Combinations of
  Thioflavine
  Rhodamine B
  Irisamine G

For greenish-yellows
  Combinations of
  Thioflavine
  Victoria Blue B

For light pink
  Rhodamine B
  Irisamine
  Rose Bengal Extra N

For purple
  Methyl Violet 3B–6B
  Crystal Violet

For sky-blue
  Victoria Blue B

For white
  Victoria Blue B (Milk-white)
  Methyl Violet 3B–6B
  Crystal Violet (Ivory-white)

To produce very delicate shades, the moist dyed skins are subjected to a
sulphur bleach overnight, to lighten the color, then rinsed, and dried.
Full, brilliant shades may be obtained by dyeing in a bath of 40° C.,
acidulated with 2–3 grams of acetic acid per liter of solution, the
following dyestuffs being suitable:

For yellow to orange
  Thioflavine
  Paraphosphine
  Rhodamine
  Safranine
  New Magenta O

For pink
  Rhodamine B
  Rose Bengal Extra N

For light red
  Safranines

For bordeaux and red
  Magenta
  New Magenta
  Russian Red
  Cerise

For violet
  Methyl Violet 6B–4R
  Crystal Violet 5B

For blue
  Victoria Blue B
  Methylene Blue BB
  New Methylene Blue N

For green
  Malachite Green Crystals
  Brilliant Green Crystals, or combinations of
  Thioflavine
  Diamond Phosphine
  Victoria Blue B

For brown
  Chrysoidines
  Bismarck Browns

In dyeing skins with harder hair than that of sheep or goat, mere killing
is insufficient to render the hair capable of taking up the dye. The
skins are therefore immersed before dyeing, in a cold, weak solution
of chloride of lime, the affinity of the hair for the dye being thereby
greatly increased.

Acid dyes are employed when a greater fastness is required than can be
obtained with the basic colors. Sulphuric acid in a quantity equal to
half the weight of the dyestuffs used, together with four times that
quantity of Glauber’s salt is added to the dyebath. Formic acid may be
used in place of the sulphuric acid, very good results being obtained.
The skins are immersed in the dyebath, and worked until thoroughly soaked
with the dye liquor, and then allowed to remain until the proper depth
of shade is attained, or overnight. The temperature of the solution is
about 40° C., and only very light shades can be produced in this manner.
In 1900 and again in 1914, the Cassella Co., a large German manufacturer
of dyestuffs, obtained patents for processes enabling the dyeing of
furs in hot solution with the acid dyes. The method required that the
skins be chrome-tanned in order to render them resistant to the action
of hot solutions, the addition of a small amount of formaldehyde to the
chrome solution increasing this effect. The skins are then treated with a
solution of chloride of lime in order to increase the affinity of the hair
for the dyestuffs. The method as it is now practised is as follows: The
skins which have been cleaned and washed are chrome tanned by the method
as described in the chapter on Tanning Methods, 60 grams of formaldehyde
being added to every 10 liters of the chrome solution. After proper
tanning the skins are rinsed, and while still moist they are subjected to
a treatment with chloride of lime. They are first immersed for 15 minutes
in a cold bath containing 120 grams of hydrochloric acid 32–36° Twaddell
per 10 liters of water, then without rinsing, they are entered into a bath
made up by adding gradually in four portions the clear solution of 2–4
grams of the chloride of lime per 10 liters of water. After working for
an hour, the skins are removed and entered again into the acid solution,
in which they are worked for another 15 minutes. In order to neutralize
and remove the last traces of the chloride of lime from the furs, they are
rinsed in a luke-warm bath containing 1–2 grams of sodium thiosulphate,
or hyposulphite of soda, in 10 liters of water. The skins are then rinsed
again, and hydro-extracted, or pressed, and are ready for dyeing. The
dyebath is prepared with the required quantity of dye, to which is added
10–20% Glauber’s salt and 2–5% acetic acid (both calculated on the weight
of the skins). The skins are entered at 20° C., then after three-quarters
of an hour to 40° C., and then after another hour slowly to 50–55° C. For
blacks, the temperature is raised as high as 65° C. After dyeing the skins
are treated with a solution containing per 10 liters

  90–120 grams of olive-oil soap
   12–25 grams olive oil
      12 grams ammonia

for 15 minutes, then hydro-extracted and dried, without further rinsing.

For this method of dyeing, the following dyes may be used:

For yellow and orange
  Fast Yellow S
  Acid Yellows
  Naphthol Yellow S
  Tropaeoline
  Orange GG, R, II, IV

For reds
  Acid Reds
  Lanafuchsine
  Azo Orseille

For violet
  Azo Wool Violet
  Acid Violets

For blue
  Cyanole FF
  Azo Wool Blue
  Naphthol Blue R
  Formyl Blue B

For green
  Naphthol Green B
  Fast Acid Green
  Cyanole Green

For brown, combinations of
  Fast Yellow S
  Acid Yellows
  Tropaeoline DD
  Orange GG
  Lanafuchsine
  Indigo Blue N
  Cyanole B
  Fast Acid Green BN

For black
  Naphthylamine Blacks
  Naphthol Blacks
  Naphthol Blue-black

For grey
  Silver Grey N
  Dyed with the addition of 1/2–1% of alum

The chrome colors are dyed on furs when very fast shades are desired, all
the fancy colors being produced in this manner, but for black, only the
acid dyes are suitable. The preparation of the skin is exactly the same as
for the acid colors, except that the treatment with chloride of lime may
be omitted, although for very full shades it is desirable. The dyeing is
carried out as follows: The dyebath is prepared with the requisite amount
of the desired dyestuff, which is previously dissolved, and to this is
added a solution of sodium bichromate, the amount of this substance being
half the weight of the dye. The solution is heated and the skins entered
and dyed for 1–2 hours at 70–80° C. Then the dyebath is exhausted by the
addition of 1/3% acetic acid, the skins being worked for another half
hour, then rinsed, hydro-extracted and dried. Any of the one-bath chrome,
or after-chrome colors may be used for this method.

Recently methods have been patented for the dyeing of furs by means of
the vat colors. Vat dyes are among the fastest coloring matters ever
produced, and their application on furs would be a great advantage, if
suitable shades could be obtained. The general process for dyeing with vat
colors, consists in reducing the dye, which is usually very insoluble,
into a soluble “leuco” compound, by means of hydrosulphites in the
presence of alkalies. The leuco compound is not a dye itself, but when
the fibre absorbs it, and is then exposed to the air, the leuco compound
is reoxidized to its original insoluble form, which remains fast and
permanent. The use of strong alkalies in vat dyeing has hitherto been a
great obstacle in the use of these dyestuffs, but in 1917, the Farbwerke
Hoechst, a large German dye works, patented a process as follows: “A
process for dyeing furs with vat colors. The dyeing is done in solutions
of the vat dyes (after the addition of gelatine or some other protective
colloid), which are rendered neutral or only slightly alkaline with
ammonia, by neutralizing the caustic soda of the solution of the leuco
compound of the vat dyes by the addition of ammonium salts, or suitable
acids. The dyeings thus obtained are uniform and fast, the leather is dyed
to only a slight degree, and shows no deleterious effects of the dyebath
on the tannage.” As a practical application of this process, another
patent was taken out by the same company, also in 1917, as follows:
“A process for producing fast blacks on furs, consisting of dyeing a
ground color with appropriate vat dyes in a hydrosulphite vat, and after
oxidation in air, topping with an Aniline or Diphenyl black. The dyeings
obtained by the combination of vat dyes which are fast to oxidizing
agents, with an oxidation black, have an appearance matching that of
logwood black in beauty; and with a dark-blue to blue-black under-color,
and a full, deep black top color, cannot be distinguished from logwood.
These dyeings also have the advantage of being faster to light than
logwood or other blacks.”

While these processes undoubtedly have many meritorious qualities which
make them interesting, they do not seem as yet, to have attained any
great practical application. However, it is a field of fur dyeing which is
worth while developing, and with certain necessary improvements in these
processes, the vat dyes may yet supersede partially some of the other
methods of dyeing furs.

CHAPTER XVII

BLEACHING OF FURS

Bleaching is for the purpose of lightening the color of furs, and is
most generally applied to white-haired skins such as white fox, ermine,
and occasionally white lambs of all kinds, and white bears. Among such
furs, pelts of a naturally pure white tone are relatively scarce, while
in the majority of cases the color ranges from a pale creamy white to a
decidedly yellowish shade. Colors which vary from the pure white detract
considerably from the attractiveness and consequent value of the fur, and
indeed, some pelts are so far off shade that they can only be used when
dyed a darker color. Most white skins which are but slightly inferior in
color can be brought to a pure white by bleaching, and they can then be
used natural. Some pelts, on the other hand, are particularly resistant
to the action of bleaching agents and cannot be sufficiently decolorized
to render them suitable for use natural, so these are also dyed. For the
production of certain delicate or fancy dyed shades on white furs, it is
often necessary to bleach the skins in order to be able to obtain pure
tones. Such instances are not very common, however. Occasionally dark
furs, such as beaver, are bleached on the tips of the hair, a golden shade
being obtained thereby, which at one time was quite popular, but recently
such effects have not been in vogue.

In the bleaching of furs, two steps may be distinguished, first
degreasing, and second, bleaching proper. In the preliminary operations
of fur dressing, the furs are treated with soap or weak alkalies to
cleanse them and to remove excess oil from the hair. During the various
processes and manipulations, the hair, especially on white skins, may
become soiled or somewhat greasy again, so it is advisable to repeat
the cleaning process. This should in every case be as light as possible,
using a weak solution of soap for the softer and cleaner pelts, or dilute
solutions of ammonium carbonate or soda ash for the more greasy-haired
skins. The skins are then thoroughly rinsed to remove all traces of
the degreasing material. This step is very essential in order to obtain
uniform bleaching.

Broadly speaking, there are two general methods which can be used in
bleaching furs, one involving the use of what are known as reducing
agents, and the other employing oxidizing substances.

Among reducing agents which can be used for bleaching furs are sulphurous
acid, and its salts such as sodium bisulphite and sodium sulphite;
hydrosulphites, and derivatives.

1. ~Sulphurous acid.~--When sulphur is burned, sulphur dioxide gas
is formed. In the presence of moisture, or when dissolved in water,
this gas forms sulphurous acid, which is one of the most commonly used
bleaching chemicals for all sorts of materials, and is very effective
for decolorizing furs. The procedure usually followed is to hang up the
moistened skins on wooden rods in a more or less cubical chamber made of
stone or brick, and lined with wood or lead. No other metals may be used,
because they are quickly corroded by the sulphurous acid. The requisite
quantity of sulphur is placed in a pot in the bleaching chamber, and then
ignited, after which the doors are shut tight. The fumes of the burning
sulphur in contact with the moist hair readily exert their bleaching
action on the furs, and the operation is allowed to proceed for six or
eight hours, or overnight. Then by means of fans or other devices, the
air filled with sulphur dioxide gas is withdrawn from the chamber, and
replaced by fresh air. The door is opened, the skins removed, exposed to
the air for a time, then rinsed, and finally dried and finished. Sometimes
one operation is not enough to sufficiently bleach the hair, so the
process is repeated. Sulphur dioxide gas can now be obtained compressed
in cylinders, which are more convenient to handle than burning sulphur.
The flow of gas which is introduced into the bleaching chamber by means
of a nozzle attached to the cylinder, can be regulated, and the bleaching
thus retarded or accelerated.

2. ~Sodium bisulphite and sodium sulphite.~--These salts of sulphurous
acid are effective in their bleaching action only when in solution in the
presence of acids. The acids liberate sulphurous acid from the salts,
so this method is virtually the same as 1. Instead of using the salts
of sulphurous acid, sulphur dioxide may be dissolved in water, and the
solution used for bleaching by immersing the furs in it. This procedure,
while consuming somewhat less time than the chamber process, is more
likely to affect the leather, which would have to be retanned. The
principle is the same as that involved in method 1.

3. ~Hydrosulphites and derivatives.~--The bleaching agent can be prepared
by adding zinc dust to commercial bisulphite of soda dissolved in about
four times its weight of water until no more reaction is evident. Milk
of lime is then added to precipitate the zinc, and the clear supernatant
liquid of 1.5°–5° Tw. is used for bleaching. The skins are immersed
for 12–24 hours, taken out, washed and finished. Instead of preparing
the hydrosulphite, the commercial products may be used with greater
convenience, a solution containing 1–4% of the hydrosulphite powder being
used, and the skins treated in this until satisfactorily bleached.

The bleaching action of sulphurous acid and hydrosulphite is supposed to
be due to the reduction of the coloring matter of the hair to a colorless
compound; or possibly to the formation of a colorless compound of the
bleaching material with the pigment. The former seems the more probable
explanation, because the change is not a permanent one, the original
natural color returning after a long exposure of the bleached fur to air
and light. However, the results are sufficiently enduring to satisfy the
requirements of the trade in the class of furs on which these methods of
bleaching are used.

Bleaching chemicals with an oxidizing action generally used for
decolorizing furs are hydrogen peroxide and peroxides; occasionally
hypochlorites and permanganates are also used.

1. ~Hydrogen peroxide.~--Hydrogen peroxide is usually employed for
bleaching in the form of its 3% solution, to which is added about 20
cubic centimeters of ammonia per liter. The ammonia serves partially to
neutralize the acid which commercial peroxide generally contains, and
also to facilitate the bleaching action. The thoroughly degreased skins
are immersed in the solution until the hair is completely wetted by it,
are then removed, and evenly pressed or hydro-extracted, after which
the pelts are hung up to dry in the air. As the hair becomes drier,
the concentration of the peroxide becomes greater, and consequently the
bleaching action is stronger. Where there is a likelihood of the leather
being affected by the bleaching solution, the ammoniacal peroxide may
be applied to the hair with a fine sponge or brush until sufficiently
wetted, and then hanging the skins up to dry. Repetition of the process
is sometimes necessary to obtain pure white, but the results are always
excellent.

2. ~Peroxides.~--The most important of these is sodium peroxide, which
comes on the market as a yellowish-white powder, which must be kept dry,
and away from any inflammable material, as fires have been caused by the
contact of the peroxide with such substances. When dissolved in water, it
is equivalent to a strongly alkaline solution of peroxide of hydrogen.

   Na₂O₂  +  2H₂O  =  H₂O₂  +  2NaOH
   sodium    water  peroxide   caustic
  peroxide             of       soda
                    hydrogen

When dissolved in acid, the alkali is neutralized, and a neutral solution
of peroxide of hydrogen and a salt is obtained, and this method is used
to obtain peroxide of hydrogen cheaply.

  Na₂O₂ + H₂SO₄ = H₂O₂ + Na₂SO₄
        sulfuric         sodium
          acid          sulphate

3 parts of sodium peroxide are slowly dissolved in a cold 1% solution of
4 parts of sulphuric acid, stirring during the addition, and making the
resulting solution neutral to litmus paper, acid or more sodium peroxide
being added as needed. There is then added 3–6 parts of a solution
of silicate of soda of 90° Tw. The skins are immersed until properly
bleached, taken out, passed through a weak acid solution, then washed
and finished. This method generally requires the leather to be retanned
after bleaching. Another process, which involves the use of peroxides,
but which is not commonly practised, consists in rubbing the hair with
a pasty mixture of equal parts of water, barium dioxide, and silicate of
soda, hanging up the skins to dry, and then beating and brushing the hair.

3. ~Permanganates.~--The only member of this group that finds practical
application for bleaching purposes is potassium permanganate. The skins
are immersed in a 0.1% solution of the crystals of potassium permanganate,
until the hair acquires a deep brown color. They are then removed, rinsed,
and entered into a second bath containing sulphurous acid in solution,
prepared by acidifying a solution of sodium bisulphite. The skins are then
worked in this until fully bleached. It is the permanganate which does
the bleaching, the sulphurous acid being for the purpose of dissolving
the brown compound of manganese formed on the hair.

4. ~Hypochlorites.~--Chloride of lime and sodium hypochlorite, which is
prepared from the former, are the chief chemicals of this type used for
bleaching. The skins are entered into a weak solution of the hypochlorite,
and left until the hair is decolorized; then after removing, they are
passed through a dilute acid, and subsequently through a weak solution of
sodium thiosulphate in order to remove all traces of the hypochlorite.
This method causes the hair to acquire a harsh feel, and the yellow
color is never entirely eliminated. The hair, however, possesses a
great affinity for certain types of dyestuffs, and it is only when
these particular classes of dyes are to be applied to the furs, that the
hypochlorite bleach is used. (See dyeing with Acid colors).

The various oxidation methods of bleaching are supposed to change the
coloring matter of the hair into an entirely different and colorless
compound which cannot return to its original form. The bleach is therefore
permanent.

In common practise, the sulphurous acid, and the peroxide of hydrogen
methods are the two chiefly employed in bleaching processes. Sulphurous
acid is used to bleach the cheaper kinds of furs, while peroxide of
hydrogen is applied to the finer furs.

Whichever process is used, it is customary to give the bleached skins a
subsequent “blueing,” by passing them through a very weak solution of a
blue or violet dye, such as indigo-carmine, crystal violet, alkali blue
or ultramarine. The furs are then dried and finished off as usual. In drum
cleaning white furs, gypsum or white sand, or sometimes even talc are used
with the sawdust, or occasionally alone without the sawdust.

BIBLIOGRAPHY

  Allen “Commercial Organic Analysis”

  Armour, B. R. “Fur Dressing and Dyeing” 1919

  ---- Color Trade Journal, Vol. 1, p. 51–53

  ---- Jour. Amer. Leather Chemists’ Assn., Vol. 13, p. 63–69.

  Belden, A. L. “Fur Trade in America” 1917

  Beltzer, F. J. G. “Industrie des Poils et Fourrures, etc.” 1912

  ---- Revue Generale des Matieres Colorantes, Vol. 12, 1908

  Bennett, H. G. “Manufacture of Leather” 1910

  Bertram, P. Deutsche Färber-Zeitung 1895–96 Heft 17, p. 266

  Bird, F. J. “American Practical Dyers’ Companion” p. 241–245

  Boerner, H. Kunststoffe, 1912 p. 223

  Brevoort, H. L. “Fur Fibres as shown in the Microscope” 1886

  Bucher, B. “Geschichte der technischen Künste” 1875–1893

  Cubaeus, P. “Das Ganze der Kürschnerei” 1912

  Davis, C. T. “Manufacture of Leather”

  Erdmann, E. Deutsche Färber-Zeitung 1894–95 Heft 21, p. 337

  ---- Zeitschrift für angewandte Chemie, 1895, Heft 14

  ---- Zeitschrift für angewandte Chemie, Heft 35, 1905

  ---- Berichte, 1904, 37, p. 2776, 2906

  Farrell, F. J. “Dyeing and Cleaning” 1912

  Fleming, L. “Practical Tanning” 1916

  Fougerat, L. “La Pelleterie dans l’antiquité, la préhistoire, etc.”

  Gardner, W. M. “Wool Dyeing” 1896

  Grandmougin, E. Zeitschrift für Farben-Industrie, 1906, 5, p. 141

  Gruene, E. Deutsche Färber-Zeitung, 1895–96 Heft 13, p. 197

  Halle “Werkstätte der heutigen Künste,” 1762, Vol. 2, p. 317

  Hartwig, O. L. “Sprengler’s Künste und Handwerke,” 1782

  Hausman, L. A. Scientific Monthly, Jan. 1920; March, 1921

  ---- Natural History, Vol. 20, 4, 1920

  ---- American Journal of Anatomy, Sept. 1920

  ---- American Naturalist, Nov.–Dec. 1920

  Hayes, A. H. National Cleaner and Dyer, Nov. 1920, p. 55–57

  Jacobson, “Schauplatz der Zeugmanufacturen” p. 493

  Jones, J. W. “Fur Farming in Canada” 1913

  Knecht, Rawson & Loewenthal “Manual of Dyeing” 1916

  Kobert, R. “Beitrage zur Geschichte des Gerbens und der
      Adstringentien” 1917

  Koenig, F. Zeitschrift für angewandte Chemie, 1914, Vol. 1, p. 529

  Lamb, J. W. Jour. Soc. Dyers & Colourists Dec. 1905, p. 323

  Lamb, M. C. “Dressing of Leather” 1908

  ---- Jour. Soc. Dyers & Colourists 1913, 29, p. 160–165

  Larish & Schmid “Das Kuerschner Handwerk” 1–3

  Laut, A. C. “The Fur Trade of America” 1921

  Lightfoot, J. “The Chemical History & Progress of Aniline Black”
      1871

  Mairet, E. M. “A Book on Vegetable Dyes” 1916

  Martin, G. “Industrial Organic Chemistry”

  Matthews, J. M. “Application of Dyestuffs” 1920

  Mayer, A. “Die Färberei in der Werkstätte des Kürschners”

  Mierzinski, S. “Die Gerb und Farbstoffextrakte”

  Noelting & Lehne “Anilin-Schwarz” 1904

  Perkins & Everest “Natural Organic Coloring Matters” 1918

  Petersen, M. “The Fur Traders & Fur-Bearing Animals” 1920

  Poland, H. “Fur-Bearing Animals in Nature and Commerce”

  Proctor, H. “Leather Industries Laboratory Book”

  ---- “Tanning”

  ---- “Making of Leather”

  Schlottauer, E. Deutsche Farber-Zeitung 1911, Heft 20, p. 397

  ---- Deutscher Färber-Kalender 1911, p. 65

  ---- Leipziger Färber-Zeitung 1909, p. 441

  Schmidt, C. H. “Handbuch der Weissgerberei”

  Setlik, B. Deutsche Färber-Zeitung 1901, p. 213

  Smith, R. W. Color Trade Journal Vol. 3, Sept. 1918, p. 304–310

  ---- Textile Recorder, Vol. 36, p. 292–293, Dec. 1918

  ---- Revue Generale des Matieres Colorantes, Vol. 23, p. 32–36

  Stevenson, C. H. “U. S. Fish Commission Report 1902–1903”, Bulletin
      No. 537

  Stickelberger, E. “Geschichte der Gerberei” 1915

  Strasser “Chemische Färberei der Rauchwaren” 1879

  Ullmann “Enzyklopedie der technischen Chemie”

  Villon, A. M. “Traité pratique de la fabrication des cuirs, etc.”
      1900

  Werner, H. “Die Kürschnerkunst” 1914

  ---- “Das Färben der Rauchwaren” 1914

  Whittaker, C. M. “Dyeing with Coal Tar Dyes” 1919

  Wiener, F. “Weissgerberei” 1877

  Witt-Lehman “Chemische Technologie der Gespinst-Fasern” 1910

  Zeidler, H. “Die moderne Lederfabrikation” 1914

INDEX

  Acetate, aluminum, 118

  ---- chromium, 120

  ---- copper, 120

  ---- ferrous, 119

  ---- lead, 126

  Acetic acid, 112

  Acid dyes, 174

  Acids, action of, on hair, 29

  ---- ---- on skin, 26

  After-treatment with copper, 168

  Alaska fox imitations, 143

  Alkaline aluminum mordants, 122

  ---- chromium mordants, 123

  ---- iron mordants, 123

  Alum, 32, 53, 118

  ---- chrome, 57

  ---- -chrome tans, 64

  ---- tans, 54, 56

  Aluminum acetate, 118

  ---- mordants, 118

  ---- sulphate, 53, 118

  Ammonia, 110

  Ammonium sulphide, 126

  Aniline black, 144

  ---- ---- by dip process, 154

  ---- ---- chemistry, 145

  ---- ---- Green’s process for, 152

  ---- ---- nature of, 144

  ---- ---- One-bath, 149

  ---- ---- Oxidation, 150

  ---- ---- processes, 149

  ---- ---- ungreenable, 148

  Aniline oil, 145

  Astrachan 5, 7, 12

  Bacteria, 51

  Badger, 7

  Ball-drum, 62

  Bandrowski’s base, 164

  Basic dyes, 171

  Beam, 38

  Beaming, 38

  Bear, black, 5, 7

  ---- brown, 5, 8

  ---- white, 8

  ---- ---- bleaching of, 179

  Beating furs, 79

  Beaver, 5, 8, 25, 83, 94

  Beechwood ashes, 108

  Bichromate of soda, 121, 147

  Black, aniline, 144

  ---- ---- by Green’s process, 152

  ---- ---- chemistry of, 145

  ---- ---- nature of, 144

  ---- ---- One-bath, 149

  ---- ---- Oxidation, 150

  ---- ---- ungreenable, 148

  Black, diphenyl, 152

  ---- logwood, 139

  ---- on Chinese goats, 141

  ---- on lambs, 141

  ---- on raccoon, 130

  ---- on skunk, 130

  ---- on wolf, 130

  Bleaching of furs, 179

  Blending, 91, 104

  Blue-grey on white furs, 142

  Blueing, 184

  Blue salt, 120

  ---- vitriol, 119

  Borax, 39, 58

  Brasilein, 135

  Brasilin, 135

  Brazilwood, 135

  Bright shades on furs, 171

  Broadtail, 8, 12

  ---- dyeing of, 139

  Brown on Thibet sheep, 169

  ---- with natural dyes, 142

  Brush process, 98

  Brushes used in dyeing, 100

  Butter, 60, 63

  Cage, 80

  Cageing, 80

  Campeachy wood, 133

  Caracul, 8, 12

  ---- dressing of, 53

  Caracul, dyeing of, 140

  Carnivorous animals, furs of, 37

  Cased skins, 36

  Castor oil, 60, 63

  Cat, civet, 5, 8

  ---- house, 8

  Caustic soda, 44, 110, 113

  Centrifugal machine, 40

  Chamber drying, 73

  Chamois dressing, 31

  ---- tan, 49, 58, 61

  Characteristics of tans, 65

  Chestnut extract, 133

  Chinchilla, 5, 6, 8, 94

  ---- blending of, 91, 104

  Chinchillone, 9

  China goat, black on, 141

  Chlorates, 147

  Chloride of lime, 174

  ---- ---- bleach, 184

  Chrome acetate, 120

  ---- alum, 57, 120

  ---- colors, 176

  ---- -copper mordant, 167

  ---- -formaldehyde tan, 64

  ---- tans, 57, 174

  Chromium mordants, 120, 166

  ---- ---- alkaline, 123

  ---- salts in tanning, 53

  Cleaning pelts, 40

  Coal tar colors, 171

  Cocoanut oil, 60

  Cod-liver oil, 60

  Collagen, 25

  Colloidal solutions, 48

  Combination tans, 49, 64

  Conveying dyed skins, 104

  Conveyor drying, 73

  Copper acetate, 119

  ---- mordants, 119, 166

  ---- salts, 109

  ---- ---- after-treatment with, 168

  ---- sulphate, 119

  Copperas, 119

  Copper-iron mordant, 167

  Coriin, 21

  Corium, 21

  Cortex, 23

  Cottonseed oil, 60, 63

  Cuba wood, 134

  Cutch, gambier, 65, 135

  Cuticle, 23

  Davy, Sir Humphrey, 47

  Degreasing furs, 179

  Diphenyl black, 152

  Dip process, 98

  Dressing of lambs, 52

  ---- ---- rabbits, 54

  ---- ---- moles, 54

  Drum, 80

  Drum-cleaning, 105

  Drumming, 76

  Drying-oils, 60

  Drying skins, 71

  Durability of furs, 5

  Dyeing furs at higher temperatures, 174

  Dyeing of imitations, 93

  ---- ---- novelty shades, 92

  ---- with aniline black, 144

  ---- ---- coal tar colors, 171

  ---- ---- mineral colors, 125

  ---- ---- oxidation colors, 155

  ---- ---- vegetable colors, 128

  Egg-yolk, 63

  Emeraldine, 145

  Enzymes, 51

  Epidermis, 21

  Erdmann, 155

  Ermine, 5, 9

  ---- bleaching of, 179

  Fahrion, 48

  Fat-glands, 21

  Fats, animal, 59

  Fermentation, 51

  Ferrous acetate, 119

  Ferrous sulphate, 119

  Finishing dyed furs, 104

  Fisher, 9

  Fitch, 9, 94

  Flat skins, 36

  Fleshing, 41

  ---- knife, 38, 42

  ---- machines, 42

  Flesh side, 22, 37

  Formaldehyde, 63

  ---- -chrome tan, 64

  ---- tans, 49, 63

  Formic acid, 44, 50

  ---- ---- as soaking agent, 39

  Fox, black on, 140

  ---- blue, 9

  ---- cross, 4, 10

  ---- grey, 10

  ---- kit, 10

  ---- red, 4, 5, 10

  ---- ---- dyed imitation silver fox, 137

  ---- silver, 4, 10

  ---- ---- imitations, 137, 143

  ---- white, 11, 94

  ---- ---- bleaching of, 179

  French seal dye, 138, 144

  Furamine dyes, 162

  Fur beating machine, 80

  Fur dressing, 30

  Fur dyeing, 91

  ---- ---- difficulties of, 95

  ---- ---- with aniline black, 144

  ---- ---- with coal tar colors, 171

  ---- ---- with mineral colors, 125

  ---- ---- with oxidation colors, 155

  ---- ---- with vegetable colors, 128

  Fur-hair, 24

  Furriers’ guilds, 34, 90

  Furrol dyes, 166

  Furs, colors of, 3

  ---- description of, 7

  ---- durability of, 5

  ---- of carnivorous animals, 37

  ---- of herbivorous animals, 37

  ---- quality of, 3, 4

  ---- uses of, 1

  ---- valuation of, 6

  ---- weight of, 5

  Fustic, 134

  ---- shades with, 135

  Gall-nuts, 128, 132

  Gambier cutch, 65, 135

  Gelatine, 1, 25, 47, 48

  Genet, 5

  Glycerine, 63

  Goat, 5, 11

  ---- logwood black on, 141

  Green’s process for aniline black, 152

  Grey-blue on white furs, 142

  Ground water, 87

  Guard-hair, 24

  Guilds, furriers’, 34, 90

  Hair, 22

  ---- action of acids on, 27

  ---- action of alkalies on, 28

  ---- action of salts on, 28

  Hamster, 3, 11

  Hardness of water, 87

  Hare, 5, 11, 94

  ---- black on, 140

  ---- blue-grey on, 142

  ---- lynx dye on, 126

  ---- stone marten imitation on, 126

  Hematein, 133

  Hematoxylin, 133

  Herbivorous animals, furs of, 37

  Hudson seal, 144

  Hydro-extraction, 40

  Hydrogen peroxide, 168

  ---- ---- bleaching with, 182

  Hydrosulphite bleach, 181

  Hypochlorites, 184

  Imitations, dyeing of, 93

  Iron mordants, 119, 167

  Iron pyrolignite, 119

  Iron salts in tanning, 53

  Iron tan, 58

  Iron vitriol, 119

  Kangaroo, 12

  Keratin, 25

  Kicker, 61

  Killing, 98, 106

  ---- formulas, 108

  ---- nature of, 107

  ---- purpose of, 106

  ---- by brush process, 111

  ---- by dip process, 111

  ---- with caustic soda, 113

  ---- with lime, 112

  ---- with soda, 112

  Knapp, 46, 57

  Knife, beaming, 38

  ---- shaving, 38

  ---- fleshing, 38

  Kolinsky, 5, 12

  Krimmer, 5, 12, 13

  Lactic acid, 44, 51

  Lactic acid fermentation, 50

  Lambs, 12

  ---- dressing of, 50, 53

  ---- dyeing of, 92, 140, 141, 142

  Lard, 60

  Lead, acetate, 126

  Lead sulphide dye, 126

  Leather, definition of, 48

  ---- dressing of, 30

  Leopard, 5, 13, 94

  ---- tanning of, 43

  Lima wood, 135

  Lime, 108, 110, 112

  Linseed oil, 60

  Litharge, 109

  Loft drying, 72

  Logwood, 133

  ---- blacks, 139

  ---- shades with, 134

  Lynx, 5, 13

  ---- imitation on rabbit and hare, 126

  Luster of hair, 23

  Machines used in brush dyeing, 102

  ---- ---- dip dyeing, 103

  Marmot, 14, 68, 94

  Marten, blending of, 91, 104

  Marten, baum, 5, 14

  ---- stone, 5, 14

  ---- ---- imitation, 126

  Medulla, 22

  Meunier, 46

  Mineral colors, 125

  ---- oils, 59, 63

  ---- tans, 49, 53

  Mink, 5, 14, 68, 94

  Mole, 5, 15

  ---- tanning of, 54

  Monkey, 15

  Mordanting, 98, 114

  Mordants, alkaline, 121

  ---- aluminum, 118

  ---- chrome-copper, 167

  ---- chromium, 120, 166

  ---- copper, 119, 166

  ---- copper-iron, 167

  ---- iron, 119, 167

  ---- tin, 121

  Mucines, 25

  Muskrat, 5, 15, 68, 94

  ---- imitation seal on, 144, 169

  Neats-foot oil, 60, 63

  Neradol D., 64

  Nigraniline, 147

  Non-drying oils, 60, 63

  Novelty shades, dyeing of, 92

  Nutgalls, 33, 132

  Nutria, 5, 15, 94

  Oiling, 62, 77

  Oils, drying, 60

  ---- non-drying, 50

  ---- partially-drying, 60, 63

  Olive oil, 60

  One-bath aniline black, 149

  Opossum, 5, 15, 68

  ---- black on, 140

  ---- skunk imitation on, 138

  ---- seal imitation on, 144

  Otter, River, 5, 16, 94

  ---- Sea, 5, 16

  Over-hair, 24

  Oxidation aniline black, 150

  ---- colors, 155

  ---- ---- shades with, 165

  Para-amido phenol, 153, 157

  Para-phenylene diamine, 153, 157, 162

  Partially-drying oils, 60, 63

  Pelage, 2

  Pelt, 2

  Pernambuco wood, 135

  Peroxide of hydrogen, 168, 182

  Peroxides, 182

  Persian lamb, 5, 12

  ---- ---- dressing of, 50, 53

  ---- ---- dyeing of, 139

  Physical theories of tanning, 47

  Pickle, 49

  Pigment granules, 23

  Pony, Russian, 5, 16

  Potassium permanganate as a dye, 127

  ---- ---- as a bleach, 183

  Protective-hair, 24

  Pyrolignite of iron, 119

  Quercitron, 135

  Quinone di-imine, 163

  Rabbit, 6, 17, 94

  ---- imitation seal on, 144

  ---- lynx imitation on, 126

  ---- sable imitation on, 168

  ---- stone marten imitation on, 126

  ---- tanning of, 54, 65

  Raccoon, 6, 17

  ---- black on, 140

  ---- skunk imitation on, 170

  Rain water, 86

  Red fox, dyed as silver fox, 137

  Redwood, 135

  Rodol colors, 165

  Russian tan, 51

  Sable, 6, 94

  ---- American, 17

  ---- blending of, 91, 104

  ---- imitation on rabbit, 168

  ---- Russian, 18

  Salammoniac, 109

  Salt, 32, 49

  ---- -acid tan, 49

  ---- -water soak, 39

  Salts, neutral, 54

  ---- basic, 54, 115

  Sawdust in drum-cleaning, 80

  “Schrot-beize,” 50

  Seal, 6, 18, 94

  ---- fur, 18

  ---- dyeing of, 92, 144

  ---- hair, 19

  ---- imitation on muskrat, 138, 169

  ---- -oil, 60

  Shearing, 82

  ---- machine, 84

  Shrinking-point of skins, 66

  ---- effect of chemicals on, 67

  Silver fox imitations, 137, 143

  Skin, 21

  ---- action of acids on, 26

  ---- action of alkalies on, 27

  Skunk, 6, 19, 94

  ---- imitation on opossum, 138

  ---- ---- on raccoon, 170

  Soaking skins, 39

  Soda ash, 110, 112

  Sodium bichromate, 121, 166

  ---- bisulphite, 127, 181

  ---- chloride, 49

  ---- peroxide, 182

  ---- sulphite, 181

  Soft water, 87

  Softening skins, 38

  Souring, 113

  Squirrel, 6, 19

  Staking, 78

  Stannous chloride, 121

  Stiasny, 64

  Stone marten imitation, 126

  Stretching, 78

  ---- machines, 78

  Sugar of lead, 126

  Sulphonated oils, 63

  Sulphuric acid, 49

  Sulphurous acid bleach, 180

  Sumach, 128, 133

  ---- tanning with, 33

  Surface water, 87

  Sweat-glands, 22

  Tallow, 60

  Tanned furs, qualities of, 48

  Tanning methods, comparison of, 65

  Tannins, 32, 132

  Tiger, 19

  Top-hair, 24

  Train oils, 63

  Tramping machine, 61

  Turmeric, 136

  Under-hair, 24

  Under-wool, 24

  Ungreenable aniline black, 148

  Unhairing, 82

  ---- machine, 83

  Ursol dyes, 157, 165

  Vanadium compounds, 147

  Vat dyes, 177

  Vegetable dyes, 128, 136

  ---- oils, 59

  ---- tans, 49, 65

  Verdigris, 120

  Water, hard, 87

  ---- soft, 87

  Whale oil, 60

  White fox, bleaching of, 179

  Wolf, 6, 19

  Wolverine, 6, 20

  Wombat, 20

  Wood dyes, 128

  Yellow wood, 134

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Transcriber’s Notes:

Punctuation has been standardised--in particular, missing periods
and quotation marks have been supplied where obviously required.
Three entries in the bibliography were located out of alphabetical
order, and have been moved accordingly (Fougerat, Lamb, Martin).
All other original errors and inconsistencies have been retained,
except as follows:

  Page 7:   changed Enclyclopedia to Encyclopedia
            (in Encyclopedia Britannica, 11th Ed.)
  Page 20:  changed Kaola to Koala
            (Koala or Australian Bear.)
  Page 62:  changed partiular to particular
            (on the particular fur treatment)
  Page 67:  changed degress to degrees
            (almost 10 degrees higher than)
  Page 73:  changed samewhat to somewhat
            (based on a somewhat different)
  Page 93:  changed imitatations to imitations
            (dyeing of imitations to a great)
  Page 101: changed diagramatically to diagrammatically
            (and B shows diagrammatically, machines)
  Page 128: changed conjuction to conjunction
            (which in conjunction with certain)
  Page 136: changed curcuma to Curcuma
            (stem of the Curcuma tinctoria,)
  Page 137: changed simutaneously to simultaneously
            (and dye simultaneously; and third)
  Page 140: changed atmopheric to atmospheric
            (aid of the atmospheric oxygen.)
  Page 142: changed followlowing to following
            (successively in the following baths:)
  Page 149: changed ozidizing to oxidizing
            (is also an oxidizing agent and)
  Page 154: changed dryig to drying
            (several times, drying each time at)
  Page 161: changed manufacurers to manufacturers
            (Other manufacturers of coal-tar)
  Page 170: changed Racoon to Raccoon
            (_Imitation Skunk on Raccoon_)
  Page 185: changed Werkstatte to Werkstätte
            (Halle “Werkstätte der heutigen)
  Page 185: changed Gerben to Gerbens
            (Geschichte des Gerbens und der)
  Page 185: changed Astringentien to Adstringentien
            (und der Adstringentien” 1917)