FUR DRESSING
DRYING AND FINISHING
One of the most important operations of all the fur dressing processes is
the drying of the skins. For even when all the previous steps have been
successfully completed, there is still a great possibility of the skin
being injured if the drying is not properly and carefully carried out.
The essential requirements for good drying are proper temperature,
uniformity and rapidity. The leather part of the fur cannot, in the
moist state, resist temperatures exceeding about 45° centigrade, for when
dried, the skin turns out hard and stiff, and cracks easily. The furs must
therefore be dried at an initial temperature of 25° to 30° centigrade, and
as the moisture is gradually removed, the temperature may be raised, for
the less water that remains in the pelt, the less is the leather affected
by the heat, and the more difficult is the removal of its aqueous content.
If the drying process is not a uniform one, that is, if all the skins
in a lot are not subjected to the same drying conditions, then after the
drying has proceeded for a certain time, some skins may be quite dry while
others are not, or there may be as many different degrees of dryness as
there are skins drying. There is also the possibility of great variation
in the amount of moisture removed from different parts of the same skin.
Such a state of affairs requires an extra expenditure of time, labor
and heat power in order to get the whole lot of furs into a more or less
uniform condition. Moreover in some kinds of furs, especially those with
thick skins, when the drying is not even, there is danger of the epidermal
layer drying away from the corium, and subsequently peeling and cracking.
Uniformity of drying requires the maintenance of a reasonably constant
temperature equally distributed throughout all parts of the space where
the drying is done, so that all the furs may be dried under the same
conditions.
Rapidity of drying is desirable not only because it is beneficial to
the condition of the pelt, but also from the point of view of practical
business economy. The space occupied by the drying should be as small
as possible compatible with the volume of work, and with the efficiency
of operation. Slow drying involves the use of much space to take care of
all the skins to be dried, or an accumulation of pelts ready to be dried,
neither of which conditions is efficient or desirable.
It was formerly the general custom, still practised in some
establishments, to dry the skins by hanging them up, leather-side out on
lines in a large room or loft, the heat being usually supplied by steam
pipes. Such a procedure occupied often as long as two or three days to
get complete drying, involved a great deal of labor, and the results were
far from uniform. In fact, in order to get the skins more nearly equable,
it was necessary to subject them to an additional operation. This usually
consisted of rotating the skins in a closed drum for several hours, the
constant intermingling of the pelts in contact with each other causing
any moisture left in them to be evenly distributed throughout the whole
lot. The skins, by this process also are rendered somewhat softer and more
flexible, but by drying under proper conditions the entire extra operation
can be dispensed with, the furs coming out quite as soft and flexible
without the drumming.
A great improvement was the adoption of large fans to circulate the heated
air in the loft, thereby approaching more nearly an even temperature.
More modern devices have, however, been developed, whereby drying can be
effected in the most uniform manner, with perfect control of temperature,
and requiring the least possible consumption of space, time, labor and
power. A typical arrangement consists of a large closed chamber, generally
constructed of steel, and divided into several compartments each of which
may be operated independently of the others. Air, heated over suitably
located steam pipes to the required temperature, is forced through the
various compartments by means of fans operated by power. The conditions
may be varied in each compartment, as to temperature or humidity, both
of which can easily be regulated, or all the compartments may be used
together as one unit. The skins are hung up on rods or lines in the
compartments, or on special frames for the purpose, which are then entered
into the compartments and the doors shut. The dry, heated air is forced
to pass over the skins, and takes up their moisture. At the further end
of the drying chamber is another fan which removes the moisture-laden air
after it has done its work. The drying is effected in from 6 to 24 hours,
and all skins are obtained in the same condition, for the process is quite
uniform and regular.
Within recent years there has been evolved a highly efficient and
economical drying equipment, based on a somewhat different principle
than underlies any of the foregoing methods. The conveyor type of dryer,
as it is called, is admirably suited to the needs of the fur dressing
and dyeing industry, and is undoubtedly superior to any of the previous
systems of drying furs, in that it affords an enormous saving of space,
time, labor and power, and gives greater uniformity and presents better
working conditions.
[Illustration: FIG. 10. DIAGRAMMATIC VIEWS OF CONVEYOR DRYER. _a._ SIDE
VIEW; _b._ END VIEW.
(_Proctor & Schwartz, Inc., Philadelphia._)]
The conveyor dryer consists essentially of a steel enclosure, through
which the skins pass on horizontal conveyors. Where special insulation
is necessary, asbestos panels are used to line the enclosure, making the
dryer absolutely fireproof, and enabling the maximum utilization of heat.
In the middle of the dryer are located the steam coils which furnish
the heat, and in many instances exhaust steam can be used as the source
of heat. Figure 10 shows diagrammatically the arrangement and operation
of the conveyor type of dryer. The enclosure is divided into several
compartments, in each of which a different condition of temperature and
humidity is maintained, the temperature being closely and accurately
regulated by an automatic control, and once the dryer has been set for
any condition, all skins will be dried exactly the same, regardless of
weather or season.
[Illustration: FIG. 11. CONVEYOR DRYER.
(_Proctor & Schwartz, Inc., Philadelphia._)]
The skins to be dried are placed on poles which in turn are set on
the horizontal conveyors as in Fig. 11. As the skins pass through the
compartments, large volumes of air, heated to the required temperature
over the steam coils, are circulated among the skins by means of the fans.
Exhaust fans, properly placed, remove a certain quantity of moisture-laden
air when it has accomplished its full measure of work. When the skins on
the conveyors have passed the full length of the dryer, they are entirely
dry, and are then removed from the poles. (Fig. 12). The time required
for drying varies according to the nature of the fur from 1–2 hours to 6–8
hours. In tests made to determine the relative efficiency of the conveyor
type of dryer as against the old “loft” method, it was found that there
was a saving of over 50% in power, and of 85% in floor space, as well as
a great saving of labor, when the conveyor system was used, the number
of skins dried in a given period of time being the same in both cases.
The advantages of the new method are easily apparent, and the saving
is sufficiently great with large lots of furs, to make an appreciable
difference in the final cost of dressing.
If the skins have been dried by a modern drying system they all come out
in a uniform condition, and are ready to go on immediately to the next
operation. If, however, a form of the “loft” method of drying has been
used, it is customary to subject the skins to an additional process. The
dried pelts are put in drums with damp sawdust, and drummed for a short
time in order to get them into the proper condition. The drumming is
essential for the purpose of equalizing the condition of the pelts, some
being drier than others, and as a consequence of the contact with the
moist sawdust, they are all brought to the same degree of dryness. As a
result of this operation also, the skins become considerably softened.
[Illustration: FIG. 12. DELIVERY END OF CONVEYOR DRYER.
(_Proctor & Schwartz, Inc., Philadelphia._)]
Then if the pelts have not been previously oiled during the tanning
process, or prior to the drying, they receive this treatment now. The oil
or fat is applied to the leather side of the furs, which are then placed
in the tramping machine for a short time in order to cause the oil to be
forced into the skin. The fibres of the corium thus become coated with a
thin layer of fatty material, which contributes greatly to the softness
and flexibility of the pelt, and increases its resistance to the action of
water, and also, in certain instances a partial chamois tan is produced,
thereby improving the quality of the leather.
[Illustration: FIG. 13. STRETCHING MACHINE FOR CASED SKINS.
(_Reliable Machine Works, Evergreen, L. I._)]
The skins are now returned to the work bench, and subjected to the
stretching or “staking” process. This consists in drawing the skin in all
directions over the edge of a dull blade, which is usually fixed upright
in a post with the edge up. Or, the stretching may be done on the fleshing
bench, substituting a dull blade for the fleshing knife. Recently staking
machines are being used in the larger establishments, the work being
done much more quickly and efficiently. As a result of this operation,
the leather becomes very soft and flexible, every bit of hardness and
stiffness being eliminated, and the skins receive their maximum stretch,
thereby giving the greatest possible surface to the pelage. This not only
helps to bring out the beauty of the hair, but is also a decided advantage
from the economic point of view, as a considerable saving of material
is effected in this way, sometimes even to the extent of twenty-five per
cent. Cased skins are stretched in a somewhat different manner, by means
of stretching irons. These consist of two long iron rods joined by a pivot
at one end. The skins are slipped on to the irons, which are then spread
apart, and in this way the skins are stretched and softened. A machine
which does this work very efficiently is shown in Fig. 13. The skin is
drawn onto the stretching arms, in this case made of bronze, which are
then forced apart by pressing on a pedal. When properly stretched to the
maximum width in all directions possible, and thus thoroughly softened,
the skin can easily be reversed, that is, turned hair-side out. As many as
6000 skins can be stretched, or 4000 to 5000 skins stretched and reversed
by one man in one day on such a machine.
[Illustration: FIG. 14. FUR BEATING MACHINE.
(_S. M. Jacoby Co., New York._)]
The pelts are then combed and beaten. In smaller plants these operations
are done by hand, but suitable machines are being employed. In order to
straighten out the hair, it is combed or brushed. Then in order to loosen
up the hair, and to cause it to display its fullness, the furs are beaten.
This process is also done by hand in some establishments, but up-to-date
places use mechanical devices for this purpose. A type of machine which
has proven very successful, and is enjoying considerable popularity
is shown in Fig. 14. These machines are also made with special suction
attachments which remove all dust as it comes out of the beaten skin,
thereby making this formerly unhealthful operation thoroughly sanitary
and hygienic.
The final process is drum-cleaning. This operation is intended
specifically for the benefit of the hair part of the fur, and is very
important inasmuch as the attractive appearance of the fur depends largely
upon it. The drum, such as is shown in Fig. 15 is generally made of wood,
or sometimes of wood covered with galvanized iron. The skins together with
fine hardwood sawdust are tumbled for 2 to 4 hours, or sometimes longer.
Occasionally a little asbestos or soapstone is added to the sawdust; for
white, or very light-colored skins, gypsum or white sand is used, either
alone, or in admixture with the sawdust; and for darker skins, graphite or
fine charcoal is sometimes added in small quantities. The drum-cleaning
process polishes the hair, giving it its full gloss and lustre, and at
the same time absorbing any oil or other undesirable matter which may be
adhering to the hair as a result of the washing and tanning processes.
Any soap, or traces of mordant are wiped off and so removed, and by using
heated sawdust, or heating the drum while rotating, the fur acquires a
fullness and play of the hair which are great desiderata in furs. The
sawdust must then be shaken out of the furs. This is done by cageing. In
some instances, the drum itself can be converted into a cage, by replacing
the solid door with one made of a wire screen. (Fig. 16.) Usually,
however, the skins are removed from the drum and put in a separate cage,
which is built like the drum, but has a wire net all around it, through
which the sawdust falls, while the skins are held back. The cages are
generally enclosed in compartments in order to prevent the sawdust from
flying about and forming a dust which would be injurious to the health of
the workers. In large establishments, the drum-cleaning machinery occupies
a large section of the plant, many drums and cages being used, and special
arrangements being made to take care of the sawdust which can be used over
again several times, until it becomes quite dirty.
[Illustration: FIG. 15. DRUM. (COMBINATION DRUM AND CAGE AS A DRUM.)
(_F. Blattner, Brooklyn, New York._)]
[Illustration: FIG. 16. CAGE. (COMBINATION DRUM AND CAGE AS A CAGE.)
(_F. Blattner, Brooklyn, New York._)]
With this operation ends the ordinary procedure of fur dressing. But
there are several additional processes required in the treatment of
certain furs, which are generally undertaken by the dresser, and chief
among these are shearing and unhairing. Sometimes this work is done in
separate establishments organized solely for this business. Certain kinds
of furs, among them being seal, beaver and nutria, possess top-hair which
may detract from the beauty of the fur, the true attractiveness being in
the fur-hair. The top-hairs are therefore removed, and for this purpose
machines are now being used. Formerly this work was all done by hand, and
on the more expensive furs like seal and beaver, unhairing is now done on
a machine operated by hand. The principle of the process is as follows:
The skins are placed on a platform and the hair blown apart by means of
a bellows. The stiff top-hairs remain standing up, and sharp knives are
brought down mechanically to the desired depth, and the hair is cut off
at that point. The skin is then moved forward a short distance, and the
process repeated until all the top-hairs have thus been cut out. With
muskrats, or other pelts which do not require such very careful attention,
the whole process is done automatically on a machine. The fur-hair is
brushed apart by means of brushes and a comb, and at regular intervals,
sharp knives cut off the top-hairs. Several hundred skins can be unhaired
in a day on such a machine requiring the attention of only one man. A
machine for unhairing skins is shown in Fig. 17.
[Illustration: FIG. 17. UNHAIRING MACHINE.
(_Seneca Machine & Tool Co., Inc., Brooklyn, N. Y._)]
With other furs, such as rabbits, hares, etc., where the trouble of
unhairing would be too great commensurate with its advantages, the hair
is sheared instead. The top hair is cut down to the same length as the
under-hair by means of shearing machines which can be regulated to cut to
any desired length of hair. A typical device for shearing furs is shown
in Fig. 18.
[Illustration: FIG. 18. FUR-SHEARING MACHINE.
(_Seneca Machine & Tool Co., Inc., Brooklyn, N. Y._)]