done to skins by some glove makers is to “feed” them with eggs--not eggs
of suspicious merits, but good enough for table use. And of these nothing
is used but the yolk. One glove maker imports from China large quantities
of the yolks of duck eggs for his work, and his yearly consumption of
yolks amounts to seventeen thousand.
When the skins leave the dyehouse, they are rapidly dried in steam-heated
lofts; and while stiff and rough they are, or were, worked into softness
and smoothness over a wooden upright standard, called a stake, at the
top of which is fitted a blunt semicircular knife. Over this the skin is
drawn by hand, back and forth, until it becomes as pliable and delicate
as silk. When this work was done manually it was most laborious. But now
it has been mostly taken over by very ingenious machinery, which looks,
in operation, as if it would tear a skin into fragments by the way it
snaps and pulls at it, but which is adjustable to such nicety of action
and power that the work is done exactly as it is wanted.
The next operation is to pare the skins to uniformity of thickness. This
also was handwork for a long time, done with a peculiarly shaped knife,
but now emery-coated wheels, with rounded edges, are used by the workers,
who, with their aid, do just as good and much faster work in drawing and
thinning the skins with absolute precision. This completes the treatment
of the skin.
Now the function of the cutter begins, and he must be a workman of
experience and good judgment, in that he must contend with the inconstant
inelasticity of the skin, reducing it to uniform resistance. He must
get so many pieces of glove size from each skin, and suit the pieces
to particular features of the skin. When done with a skin he must have
left, as useless, only trifling strips and shreds. The shapeliness of
the glove which a woman draws over her hand, depends altogether upon the
intelligence and skill of the cutter. In American factories the cutter is
usually from some glove-making center in Europe and from a family whose
occupation has been glove making for centuries.
A punch next cuts these glove pieces into shape, forming and dividing the
fingers, slitting the buttonholes, providing side pieces for fingers and
thumbs, and also the fragments used for strengthening the buttonholes.
The sewing, formerly the handiwork of women, is now done on machines
of capacity for exceptionally fine quality of intricate stitching. The
number of glove sizes made is sufficient to meet every likely demand.
When sewn, and the buttons or fastenings put on, they pass beneath the
critical eye of an inspector for scrutiny as to faults. Then they are
finally shaped on a hot metal hand, smoothed, banded, boxed, and sent to
the salesroom for shipment.
The first and fourth fingers of a glove are completed by gussets, or
strips, sewed only on the inner side; but the second and third fingers
require gussets on both sides to complete the fingers. In addition to
these, small, diamond-shaped pieces are sewed in at the roots of the
fingers. Special care is necessary in sewing in the thumb pieces, as
poorly made gloves usually give way at this point.
Natural lined gloves are now common enough, although it is not many years
since they were regarded as impracticable. These are made from pelts of
various animals with the hair left on the skin to form the lining.
AUTOMOBILE AND FURNITURE LEATHER
For automobile and furniture leather only choice hides should be used.
The kind of hides generally employed for this class of leather are French
and Swiss, as these run full and plump on the bellies, are free from cuts
on the flesh and are of clear grain. The hides are trimmed before placing
them in the soaking pits, all useless parts, such as nose, shanks, etc.,
being cut away.
After remaining in soak for a day or two, the hides are hauled out,
fleshed, and returned to the soaks for thorough softening. When
thoroughly soaked, they are toggled and reeled into the first lime. The
first lime must be a weak, mellow lime, or a harsh grain will show after
the leather is tanned. The hides are reeled over into stronger limes
every day for seven days, when they are ready for unhairing. After coming
from the limes, the hides should go into a pit of soft water heated to
about ninety degrees Fahrenheit and left over night before starting in
to unhair. After unhairing, they are thrown into a vat of clean water
and thoroughly worked out on the grain to remove short hairs and scud
and are then ready for bating. One that has a little bacterial action
is preferred to an acid bate. After bating, the hides are given a good
scudding on the grain and are then ready for the tanning liquors.
The liquors are made of hemlock and oak and are used very weak on the
start. The hides are suspended for a day in a liquor not over six degrees
specific gravity reading in strength, and the following day shifted over
into a stronger liquor. The stock is given stronger liquors every day
until tanned enough for splitting.
The stock is struck out smoothly and brought to the machine for
splitting. The buffing is first taken away and sold for hat bands,
pocket-books, etc. The grains are finished and the splits are returned to
the tanning liquors to be thoroughly tanned. As soon as the splits are
tanned, they are washed up, drained, and then drummed in the drum in a
sumac liquor. They are now scoured, and, after being well set out, are
given a good oiling with cod oil.
They are now tacked out on the frames and dried out. They are next taken
from the frames and boarded by hand over the table. The splits are taken
to the japan shop and are tacked out again and are ready for the first
coat of daub. Two coats are applied. After each coat, the splits are well
rubbed down, when they receive the slicker coat. The color coats are now
applied, and after drying out, the leather is grained up and finished.
CHAPTER ELEVEN
RUBBER SHOE MANUFACTURE
Examine the rubbers we wear during the winter and stormy weather.
Rubber shoe coverings are made to protect the shoe from water and snow
and may be in the form of either slippers or arctics. The covering is
rendered waterproof by means of a compound rubber.
Rubber is the name given to a coagulated milky juice obtained from many
different trees, vines, and shrubs that grow on that part of the earth’s
surface which forms a band some three or four hundred miles on either
side of the equator.
[Illustration: Crude Rubber.]
Rubber is graded commercially, according to the district where it is
found. In the order of importance it may be divided into three general
sorts, viz., American, African, and Asiatic. The best and largest
quantities of rubber come from Brazil, along the banks of the Amazon
River. The countries in the northern and western part of South America,
and the Central American States and Mexico furnish considerable rubber.
Eastern and western Africa also produce many kinds of rubber in large
quantities, though somewhat inferior to the Brazilian product. The
Asiatic rubbers are unimportant in quantity, and, excepting the rubber
obtained from cultivated trees in Ceylon, are decidedly inferior in
quality.
The fluid rubber obtained from Brazil is called Para and is used
principally in the manufacture of rubber footwear. The method of
gathering and coagulating the rubber juice (called latex) varies in the
different countries. The native first clears a space under a number of
trees and proceeds to tap the trees with a short-handled ax, having a
small blade, by cutting gashes in the bark. A cup is fixed under each
cut to catch the fluid as it flows out. As fast as the cups are filled,
they are emptied into a large vessel and carried to the camp to be
coagulated. A fire is started in a shallow hole in the ground, and palm
nuts, which make a dense smoke, are thrown on. An earthen cover which has
a small opening on top is placed over the fire, allowing the smoke to
escape through the opening. A wooden paddle is first dipped in clay water
and then into the latex and then held over the smoke. The heat coagulates
a thin layer of rubber on the paddle. It is dipped again and again in the
latex and smoked each time. After being dipped many times, a lump (called
biscuit) of rubber is formed. A cut is made in the biscuit and the paddle
removed. Then the rubber is ready for market. The world’s crop of rubber
in 1911 was about ninety thousand tons.
Few people realize the number of operations necessary to produce from the
crude biscuit of India rubber the highly finished rubber shoe of to-day.
Briefly stated, the various steps are washing, drying, compounding,
calendering, cutting the various parts, making or putting these parts
together, varnishing, vulcanizing, and packing. Each of these processes
requires a distinct and separate department, and many of these processes
are subdivided into minor operations.
The huge stock of Para rubber, that is rubber obtained from the Amazon
section, to be found in any of the leading rubber factories counts well
up into the thousands of dollars. With rubber at or near $1.50 per pound,
a stock of ten to fifty tons runs up into the five or six figures.
This crude rubber, as it comes from the Amazon, contains more or less
dirt, pebbles, and other foreign substances, which must be removed.
The large cakes of crude rubber are first broken up by a cracker machine,
consisting of two large, revolving steel cylinders, from which the
product falls into pans or trays. It goes then to a machine known as a
“washer” or “sheeter,” where it is run between revolving cylinders, upon
which a continuous spray of clean water is maintained. After being rolled
into rough sheets, it is put into a tank, from which it is taken to the
“beater” machine, in which water runs continuously, and then it is washed
again and “sheeted out.” It is then dried in one of two ways.
(1) The older way. The sheets are hung over rods in a large room, and
allowed to dry in the air. To facilitate the same, a fan or blower is
often used to cause a circulation and removal of the moisture-laden air.
This requires a period of from one to two or three months.
[Illustration: Washing and Drying.]
(2) The second method is called vacuum drying. This process is gradually
being introduced, so that now probably more rubber is dried in vacuum
than by air. The vacuum drier consists of a large iron cylinder filled
with plates, through which steam is allowed to circulate. The rubber
is placed on the plates and the air is exhausted from the cylinder by
means of an air pump until very nearly twenty-six degrees of vacuum are
obtained. By this process only from two to three hours are required to
produce perfectly dry rubber.
The making of a rubber shoe is not the simple matter which might at
first be supposed. An ordinary rubber shoe consists of at least seven
or eight different parts, sometimes twenty-one parts to a pair, while
a high-button gaiter has seventeen distinct parts, and a rubber boot
has twenty-three different pieces. There are insoles, outsoles, stays,
piping, foxing, and a dozen other different pieces, each one of which
is necessary to the proper construction of a rubber shoe or boot. The
thinner sheets for the uppers are cut by hand, the deft work of the
cutters in following the patterns outlined on the sheets being the result
of years of practice. The sheets of rubber from which the uppers and
soles are cut are at this stage of the work plastic and very sticky. It
is necessary on this account to cut the various pieces one by one, and
keep them separate. The soles and some of the heavier pieces are dried
out by the machine, and the heels are made by a special machine, but by
far the greater part is done by wonderfully skilled hands. All of these
parts which go to make a shoe, or the twenty-three parts which go into
a boot, are collected and sent to the making department, which, in most
factories, is a large room containing several hundred operatives, each
working by herself, and bringing the many separate parts into the fully
finished footwear.
[Illustration: Calender Room.]
The sheets of rubber, after being dried, are taken to the “compound”
room, where they are sprinkled with whiting, to prevent sticking, and
weighed. Next they are taken into the calender room to a “mixer,” by
means of which the rubber is combined with other substances, which
include sulphur, litharge, whiting, lampblack, tar, resin, lime, palm
oil, and linseed oil.
There are different calendering machines. The ones called the upper
calenders form sheets of rubber stock for the upper part of the shoe. The
soling calenders form the stock for the sole or bottom part of the shoe;
other calender machines are used to coat a layer of gum on one side of
the fabrics used for lining and various strips, fillers, toe, and heel
pieces. The gum sheets are sent to the cutting room.
Generally, linings for nine pairs of shoes are cut at once. The linings
are cut both by hand and by machine. Men who cut with dies, by hand,
stand at the bench and use iron mallets, like those used in cutting
heels. Inner soles, heel pieces, and linings are all cut by means of dies
in the same manner.
The edges of the several parts are spread with cement, and then the
parts are taken to the making room and distributed. In the making
department the boots and shoes are put together. Women make the light
overshoes; men make the heavy ones. Rubbers are made by women, but men
put on the outer soles.
Linings are first applied smoothly to a wooden last and cemented
together, the cement side out. The rubber parts are then stuck on and
rolled firmly with a small hand roller. Young women become very skilled
in this work, taking up the several parts in rapid succession, placing
them accurately upon the last, and rolling and pounding them firmly
together.
[Illustration: Cutting Room.]
Perhaps the most interesting single process is that of putting the rubber
boot together. This work is done by men, and requires, in addition
to accurate eyesight, rapid and very deft movements of the hand and
considerable strength. No nails, tacks, or stitching are required. The
natural adhesiveness of the rubber, assisted by the use of rubber
cement, holds the parts solidly together.
In the making of the shoe the last is covered with the various pieces
which are so made as to adhere where they are placed. It is exact and
nice work fitting all these pieces perfectly, each edge overlapping just
so far and no farther. The lighter shoes are made by women, but the heavy
lumbermen’s shoes, arctics, and especially the boots, are made by men,
for this work needs strength as well as dexterity.
The goods which require varnishing are put on racks and treated with a
mixture of boiled linseed oil, naphtha, and other materials, which are
applied with brushes, and impart a gloss to the surface.
On vulcanizing boots and shoes, the shoes are placed on racks supported
by iron cars, which are run over tracks into the vulcanizing chamber.
This consists principally of a large room provided with a steam coil on
the floor. The temperature rarely exceeds two hundred and sixty degrees
Fahrenheit. In vulcanizing shoes, the heat is increased gradually from
the beginning, about one hundred and eighty degrees Fahrenheit, otherwise
the goods would be blistered, due to the rapid evaporation of moisture
and other volatile constituents. They are kept in these heaters from six
to seven hours. This causes a union of sulphur and rubber, which is not
affected by heat or cold.
They are wheeled on another truck to the packing room, where they are
inspected, taken from the lasts, tied together in pairs, or placed in
cartons, as the case may be. They are then sent to the shipping room to
be packed in cases ready to be delivered to the cars waiting at a side
track of the railroad, or sent to the storehouse until they shall be
called for by the jobbers or retail dealers.
An important branch of the rubber business is the manufacture of tennis
shoes. This is a generic term, which is applied to all kinds of footwear
having cloth tops and rubber soles. As the name indicates, they were
first used in playing the game of tennis, but they have come into very
general use as warm weather and vacation shoes, and every year shows
an increased popularity. These shoes are made in a similar manner to
the rubber shoes, the rubber soles being cemented to the cloth uppers
and vulcanized the same as the rubber overshoes. Many different styles
are made, and each year shows some improvements in the shapes, in the
textiles which are used, in the colors and combinations of soles and
uppers.
Rubber shoes should not be expected to give satisfactory service unless
properly fitted. If too short, too narrow, or if worn over leathers
with extra heavy taps, or unusually thick, wide soles, strains will be
brought upon parts not designed to stand them and the rubber will give
way. Rubber goods, particularly boots, if too large will wrinkle and a
continued wrinkling and bending is liable to cause cracking.
Extreme heat or cold should be avoided. Rubber boots or shoes should
never be dried by placing them near a heater of any kind. If left near
a stove, register, or radiator, the rubber is liable to dry and crack.
If left out of doors in winter, or in an extremely cold place, they will
freeze. Then when the warm foot is put into them and the rubbers are
worn, the rubber will crack.
Oil, grease, milk, or blood will cause rubber to decay in a very short
time. If spattered with any of these, the rubber should be promptly and
thoroughly cleaned with warm water and soap.
The oil in leather tops will rot rubber, so that care should be taken
in storing and packing to prevent the leather and rubber from coming in
contact.
[Illustration: Putting together the Parts of a Rubber Shoe.]
Various heavy goods are advertised as proof against snagging. It should
be remembered, however, that no rubber can be made strong enough to be
absolutely proof against tearing or puncturing by extremely sharp edges,
such as stiff stubble, sharp-edged rocks, broken glass, etc.
Mud, barnyard dirt, or filth of any kind should never be allowed to dry
on rubbers. They should be cleaned as carefully as leather boots or shoes.
Exposure to strong sunlight for any length of time produces an effect on
rubbers similar to that of putting them near a stove or radiator. Rubbers
should not be left in the sun to dry. When not in use they should be kept
in a cool, dark place.
RUBBER HEELS
Rubber heels are generally made for boots and shoes as follows. The
compounded rubber is sheeted on a calender roll, on a drum, until
several layers are obtained, thus making a sheet of about one inch in
thickness. The heel is cut out from this sheet by means of a die and
placed in a mold. It is there subjected to an extremely high pressure,
generally obtained by hydraulic power. The plates of the press are heated
with live steam. The heels are removed at the end of nine or ten minutes
and the sheet which was formerly nearly an inch in thickness is now only
about half an inch and has by pressure been molded into the shape of the
heel desired, is semi or partially vulcanized, and also is imprinted upon
the bottom with the name or other brand of the company.
The cup-shaped portion of the heel is now coated with a layer of rubber
cement, and firmly placed on the boot ready to go to the vulcanizer,
where vulcanizing of the heel is then completed.
[Illustration: Heel-making Department.]
Many articles of rubber are vulcanized by the use of chloride of sulphur,
which process is sometimes known as “cold cure.” The action of sulphur
chloride itself is so violent that it must be diluted, and for this
purpose carbon bisulfide is often used. In some cases, as, for example,
the manufacture of tobacco pouches, the articles are submerged for from
one to two minutes in the liquid, then removed and washed thoroughly. In
another case, as in the manufacture of some kinds of rubber cloth, such
as hospital sheeting, the coated cloth is suspended in a suitable room
and the chloride of sulphur and carbon bisulfide mixed and evaporated
by action of heat so that the cloth is subjected to the action of vapor
alone. Only articles with comparatively thin walls can be successfully
vulcanized by the cold cure, as at best the vulcanizing action of the
chloride is only superficial.
No account of vulcanization processes as employed in the manufacture of
rubber goods is complete without the mention of “steam cure.” A great
variety of rubber goods under the general term of mechanical sundries
are cured by this method. This includes rubber matting, door mats, water
bottles, druggists’ sundries, etc. This process consists in brief of
submitting the articles to be vulcanized to the action of live steam
for from half an hour to an hour, or until the goods are thoroughly
vulcanized. The temperature and duration of time required depend to a
considerable extent upon the thickness of the walls of the article. In
order to prevent the goods from being pitted and damaged by the action of
steam, they are wrapped with cloth or imbedded in pans of soapstone. A
great variety of rubber tubing is cured by this method.
In rubber cloth making, the crude rubber is put through the washing
process, dried and mixed with sulphur, litharge, coloring matter, etc.,
and then is taken to the cement room, where it is “cut” with naphtha,
forming a thick paste or dough. This is taken to the spreading room in
large tubs and fed into the roller machine, which is like a long table
made of steam pipes placed horizontally in a single layer. Below one end
is a roll of cloth, which is passed between two iron rollers on the end.
The dough is fed in between these rollers and is spread smoothly over
the cloth, which is rolled up and removed to a heating room, where it
is unrolled and hung on racks, and then subjected to sufficient heat to
cause the combination of the sulphur and rubber.
CHEMISTRY IN THE MANUFACTURE OF RUBBER GOODS
Too much stress cannot be laid upon the importance in all rubber
factories of the chemical department. During the last two or three years
there has been an unusual development along these lines, and to-day no
factory for the manufacture of rubber goods is complete that does not
possess a well-equipped laboratory. Not only does this department enable
the manufacturer to control the purity and uniformity of his compounding
ingredients and the innumerable grades of crude rubber, but, what is of
even greater importance, it enables him to inaugurate research work as
applied to his particular line of manufacture. This part of laboratory
work is already producing results not only of scientific interest, but of
very great practical and economic value. Still another rôle of the modern
chemical laboratory is to exercise a control over the finished material,
so that the manager of the works may be in possession daily of reasons
for any variation detrimental to the standard of his products.
RUBBER TERMS
ANKLE PIECE. A large piece of light sheeted gum, which goes around the
ankle and extends about halfway up the leg.
BACK STAY. A piece of frictioned sheeting similar to the side stay in
shape and placed at the back of the heel and ankle.
GUM COUNTER. A piece cut out of sheeted gum, on the under side of which
is placed a counter form or a piece of frictioned sheeting.
OUTER FILLER. A filling sole cut from rag-coated or frictioned sheeting,
and designed to fill up the hollow on the bottom caused by bringing the
edges of the gum vamp and counter underneath.
INNER SOLE. Usually made of felt or sheeting coated on one side with
rag stock. In lasting up, the bottom edges of the lining (which have
previously been cemented) are pulled under and adhere to the inner sole.
LEG COVER. A piece of sheeted gum rolled upon a piece of frictioned
sheeting called the leg form.
LEG LINING. The lining, usually of felt or wool netting, for the leg.
PARA. A name given to rubber from Brazil.
PIPING. Strips of frictioned sheeting used to join the lining together
over the instep and up the back, and also to hold the lining up on the
tree by passing a strip over the top.
RAG COUNTER. Quarter stiff is a counter piece cut out of rag-coated or
frictioned sheeting, which gives stiffness to the counter.