A MANUAL OF SHOEMAKING

A MANUAL
OF
SHOEMAKING
AND
LEATHER AND RUBBER
PRODUCTS

BY
WILLIAM H. DOOLEY
PRINCIPAL OF THE LOWELL INDUSTRIAL SCHOOL

ILLUSTRATED

BOSTON
LITTLE, BROWN, AND COMPANY
1912

Copyright, 1912,
By Little, Brown, and Company.

All rights reserved.

Published, September, 1912.

PREFACE

The author was asked in 1908 by the Lynn Commission on Industrial Education to make an investigation of European shoe schools and to assist the Commission in preparing a course of study for the proposed shoe school in the city of Lynn. A close investigation showed that there were several textbooks on shoemaking published in Europe, but that no general textbook on shoemaking had been issued in this country adapted to meet the needs of industrial, trade, and commercial schools or those who have just entered the rubber, shoe, and leather trades. This book is written to meet this need. Others may find it of interest.

The author is under obligations to the following persons and firms for information and assistance in preparing the book, and for permission to reproduce photographs and information from their publications: Mr. J. H. Finn, Mr. Frank L. West, Head of Shoemaking Department, Tuskegee, Ala., Mr. Louis Fleming, Mr. F. Garrison, President of Shoe and Leather Gazette, Mr. Arthur L. Evans, The Shoeman, Mr. Charles F. Cahill, United Shoe Machinery Company, Hood Rubber Company, Bliss Shoe Company, American Hide and Leather Company, Regal Shoe Company, the publishers of Hide and Leather, American Shoemaking, Shoe Repairing, Boot and Shoe Recorder, The Weekly Bulletin, and the New York Leather Belting Company.

In addition, the author desires to acknowledge his indebtedness to the great body of foreign literature on the different subjects from which information has been obtained.

CONTENTS

LIST OF ILLUSTRATIONS

SHOEMAKING

CHAPTER ONE
FUNDAMENTAL SHOE TERMS

Before explaining the manufacture of shoes, it is necessary to fix definitely in our minds the names of their different parts. Examine your shoes and note the parts that are here described.

The bottom of the shoe is called the sole. The part above the sole is called the upper. The top of the shoe is that part measured by the lacing which covers the ankle and the instep. The vamp is that section which covers the sides of the foot and the toes. The shank is that part of the sole of the shoe between the heel and the ball. This name is often applied to a piece of metal or other substance in that part of the sole, intended to give support to the arch of the foot. The throat of the vamp is that part which curves around the lower edge of the top, where the lacing starts.

Backstay is a term used to denote a strip of leather covering and strengthening the back seam of the shoe. Quarter is a term used mostly in low shoes to denote the rear part of the upper when a full vamp is not used. Button fly is the portion of the upper containing the buttonholes of a button shoe. Tip is the toe piece of a shoe, stitched to the vamp and outside of it. The lace stay is a term used to denote a strip of leather reënforcing the eyelet holes. Tongue denotes a narrow strip of leather used on all lace shoes to protect the instep from the lacing and weather.

Foxing is the name applied to leather of the upper that extends from the sole to the laces in front, and to about the height of the counter in the back, being the length of the upper. It may be in one or more pieces, and is often cut down to the shank in circular form. If in two pieces, that part covering the counter is called a heel fox. Overlay is a term applied to leather attached to the upper part of the vamp of a slipper. The breast of the heel is the inner part of the heel, that is, the section nearest the shank.

CHAPTER TWO
HIDES AND THEIR TREATMENT

If we examine our shoes, we will find that the different parts are composed of material called leather. The bottom of the shoe is of hard leather, while the part above the sole is of a softer, more pliable leather. This leather is nothing more than the hides of different animals treated in such a way as to remove the fat and the hair.

After the hides have been taken from the dead body of the animal, they are quite heavily salted to preserve them from spoiling. In this salted condition they are shipped to the tanneries.

The process or series of processes by which the hides and skins of animals are converted into leather is called tanning. The process may be divided into three groups of subprocesses as follows:—

Beamhouse process, which removes the hair from the hides and prepares them for the actual process of the tanning or conversion into leather; tanning, which converts the raw hide into leather; and finishing, which involves a number of operations, the objects of which are to give the leather the color that may be desired and also to make it of uniform thickness, and impart to it the softness and the finish that is required for a particular purpose.

Hides are divided roughly in the tannery, according to the size, into three general classes:—

(1) Hides, skins from fully grown animals, as cows, oxen, horses, buffaloes, walrus, etc. These are thick, heavy leather, used for shoe soles, large machinery belting, trunks, etc., where stiffness, strength, and wearing qualities are desired. The untanned hides weigh from twenty-five to sixty pounds.

(2) Kips, skins of the undersized animals of the above group, weighing between fifteen and twenty-five pounds.

(3) Skins from small animals, such as calves, sheep, goats, dogs, etc. This last group gives a light, but strong and pliable leather, which may be used for a great many purposes, such as men’s shoes and the heavier grades of women’s shoes.

The hides, kips, and skins are divided into various grades, according to their weight, size, condition, and quality.

The quality of the hides not only depends upon the kind of animal, but also upon its fodder and mode of living. The hides of wild cattle yield a more compact and stronger leather than those of our domesticated beasts. Among these latter the stall-fed have better hides than the meadow-fed, or grazing cattle. The thickness of the hide varies considerably on different animals and on the parts of the body, the thickest part of the bull being near the head and the middle of the back, while at the belly the hide is thinnest. These differences are less conspicuous in sheep, goats, and calves. As regards sheep, it would appear that their skin is generally thinnest where their wool is longest.

In the raw, untanned state, and with the hair still on, the hides are termed “green” or “fresh.” Fresh, or green hides are supplied to the tanners by the packers or the butchers, or are imported, either dry or salted.

Hides are obtained either from the regular packing houses or from farmers who kill their own stock, and do not skin the animal as scientifically as the regular packing houses, in which case they are called country hides. There are different grades of hides and leather, and these different grades are divided in the commercial world into the five following grades:—

I. NATIVE HIDES

• Native Steers
• Native Cows, heavy
• Native Cows, light
• Branded Cows
• Butts
• Colorado Steers
• Texas Steers, heavy
• Texas Steers, light
• Texas Steers, ex-light
• Native Bulls
• Branded Bulls

II. COUNTRY HIDES

• Ohio Buffs
• Ohio Ex.
• Southerns

III. DRY HIDES

(Raised on plain. Rough side suitable for soles.)

• Buenos Ayres

IV. CALFSKINS

(Green salted)

• Chicago City

V. PARIS CITY CALFSKINS

• Light
• Medium
• Heavy

Hides obtained from steers raised on Western farms are known as native steer hides.

Native cowhide (heavy) is hide weighing from fifty-five to sixty-five pounds, obtained from cows.

Native cowhide (light) is cowhide weighing under fifty-five pounds.

Branded cowhide is hide obtained from cows that are branded on the face of the hide.

Butts is a term applied to the part of the hide remaining after cutting off the head, shoulders, and strip of the belly.

Colorado steer hide is from Colorado steers, which are very light.

Texas steer hide comes in three grades, heavy, light, and extra light. The heavy grade is very heavy because the animal is allowed to graze on the plains. That is the reason why it is heavier than the Colorado steer hide, which is raised on the farm.

Bull hide is divided into two classes, the regular hide and the branded grade. The branded grade usually is one cent a pound less than the regular.

Country hides are of three grades, Ohio Buffs, Ohio Ex., and Southern. The Ohio Buffs weigh from forty to sixty pounds. The Ohio Ex. weighs from twenty to forty pounds. Southern hides have spots without hair and other blemishes on them, due to the sting of insects. This makes the Southern hide inferior to the Ohio, Indiana, Michigan, and Chicago hides that have no such blemishes. Ohio Butt hides are the best, because in Ohio they kill a great many young calves, while in Chicago young cows (that have calved) are killed, causing the hide to be flanky.

The season of the year in which cattle are slaughtered has considerable influence upon both the weight and condition of the hide. During the winter months, by reason of the hair being longer and thicker, the hide is heavier, ranging from seventy-five to eighty pounds, and gradually decreasing in weight as the season becomes warmer and the coat is shed, until in June and July it weighs from seventy down to fifty-five pounds, the hair then being thin and short. The best hides of the year are October hides, and short-haired hides are better for leather purposes than long-haired ones.

A thick hide which is to be used for upper leather is cut into sides before the tanning process is completed. This is performed by passing it between rollers where it comes in contact with a sharp knife-edge, which splits it into two or more sheets. Great care must be exercised in cutting the leather in order to have good “splits” (sheets of leather). A split from a heavy hide is not as good as a whole of a lighter leather.

Butts and backs are selected from the stoutest and heaviest oxhides. The butt is formed by cutting off the head, the shoulder, and the strip of the belly. The butt or back of oxhide forms the stoutest and heaviest leather, such as is used for soles of boots, harness, etc.

Hides and skins are received at the tannery in one of three conditions, viz. green-salted, dry, or dry-salted. Very few hides are received by tanners in fresh or unsalted condition, salt being necessary to preserve them from decay. Green-salted hides are those that have been salted in fresh condition, tied up in bundles, and shipped to the tanner. Dry hides are those that were taken from the carcass and dried without being salted; these are usually stiff and hard. Dry-salted hides are hides that were heavily salted while they were fresh, and then dried. The hides and skins that are received from the slaughterhouses of this country are almost invariably green-salted; those from foreign countries are green-salted, dry, and dry-salted.

It does not matter in what condition the hides are received or the kind of leather into which they are to be tanned; they all require soaking in water before any attempt is made to remove the hair or to tan them. The object of the soaking process, as it is called, is to thoroughly soften the hides and to remove from them all salt, dirt, blood, etc. Ordinary hides are usually soaked from twenty-four to forty-eight hours. Dry hides require much longer. The water should be changed once or twice during the process, since dirty water may injure the hides. Soft water is better than hard for this process. Where the water is hard, it is customary for the tanner to add a quantity of borax to it to increase its cleansing power and to hasten the softening of the hides.

When dry hides have become soft enough to bend without cracking, they are put into a machine and beaten and rolled, then soaked again until they are soft and pliable. It is very important that all the salt and dirt are removed during the process of soaking, as they injure the quality of the leather if they are not removed before the hides are unhaired. When the soaking process is completed, the lumps of fat and flesh that may have been left on by the butcher are removed by hand or by a machine, and the hides are then in condition to be passed along into the next process. The parts that cannot be made into leather, such as tails, teats, etc., are trimmed off before the hides are soaked. Large hides are cut into two pieces or halves, called “sides,” after they have been soaked.

For the purpose of taking the hair from the hides and skins, lime, sulphide of sodium, and red arsenic are used. Lime is sometimes used alone, but usually one of the other two chemicals is mixed with it. The lime is dissolved in hot water, a quantity of either sulphide of sodium or red arsenic is added to it, and the solution is then mixed with water in a vat, the hides being immersed in this liquor until the hair can be easily removed. The action of the unhairing liquor is to swell the hides, then to dissolve the perishable animal portion and loosen the hair so that it can be rubbed or pulled off.

There are several different processes of unhairing the hides. Each tanner uses the process that will help to give the leather the qualities that it should have, such as softness and pliability for shoe and glove leather, or firmness and solidity for sole and belting leather. This is one of the most important in the series of tannery processes, and if the hides are not unhaired properly and not prepared for tanning as they should be, the leather will not be right when it is tanned and finished.

There is also a process of unhairing, called “sweating,” which softens the hide and loosens the hair so that it can be scraped off. In this process the hides begin to decay before the hair is loose; it is therefore a dangerous process to use and must be carefully watched or the hides will be entirely spoiled. Sweating is never used for the finer, softer kinds of leather. It is applied chiefly to dry hides for sole, lace, and belt leather. It is an old-fashioned process and is not used as much nowadays as some years ago.

The pelts of sheep are salted at the slaughterhouses and then shipped to the tannery. Here they are thrown into water and left to soak twenty-four hours to loosen the dirt and dissolve the salt. The pelts are next passed through machines that clean the wool, and any particles of flesh remaining on the inner or flesh side are removed. The pelts are then in condition to have the wool removed. As long as a sheepskin has the wool upon it, it is called a pelt; as soon as the wool has been taken off, it is called a skin or a “slat.”

Each pelt is spread out smoothly on a table with the wool down and the inner or flesh side up. A mixture of lime and sulphide of sodium is next applied uniformly over the skin with a brush. The pelt is then folded up and placed in a pile with others. The solution that was applied penetrates the skin and loosens the wool, which, at the end of twenty-four hours, more or less, can be easily pulled off with the hands or rubbed off with a dull instrument or stick. The workman must be careful not to get any of the solution on to the wool, as it dissolves it and makes it worthless. Since the wool is valuable, the solution must be applied to the flesh side very carefully so that it does no injury. The wool that is removed from the skins is called “pulled wool.”

The slat is now ready to be limed, washed, pickled, and tanned. Heavy skins are often split into two sheets after they have been limed. The part from the wool side is called a skiver, and that from the flesh side is called a flesher.

After the skins have been limed, they are bated and washed, which makes them soft, clean, and white; they are then put into a solution of salt, sulphuric acid, and water, called “pickle,” and after a few hours they are taken out, drained, and tanned.

Large quantities of sheepskins are sold to tanners in the pickled condition by those who make a business of preparing such skins and selling the wool. Pickled skins can be kept an indefinite length of time without spoiling; they can also be dried and worked out into a cheap white leather without any further tanning whatever. Most of such skins, however, are sold to tanners, who tan them into leather. Sheepskins contain considerable grease, which must be removed before the leather can be sold.

For some processes of tanning, calfskins, goatskins, and cattle hides are also pickled the same as sheepskins; for other processes they are not pickled, but are thoroughly bated or delimed, washed, and cleansed. Heavy hides are sometimes split out of the lime; more frequently, however, they are not split until after they have been tanned.

To capitulate, the preparatory processes may be briefly described as follows:—

Soaking, which dissolves the salt, removes the dirt and makes the hides soft and comparatively clean.

Liming and unhairing, which swell the hides and dissolve the perishable animal portion, loosen the hair, and put the hides into proper condition for tanning. Hides tanned without liming, even if the hair is removed by some chemical, do not make pliable leather, but are stiff and hard.

Bating, which removes the lime from the hides.

Pickling, which helps in the tanning later, and keeps the hides and skins from spoiling if they are not tanned at once.

The lumps of fat and flesh that may be on the hides are removed by machinery or by placing the hide over a beam and scraping it with a knife. The hair, when it is loosened by the lime, is removed by a machine or by hand.

CHAPTER THREE
PROCESSES OF TANNING

The various processes of tanning may be roughly divided into two classes, vegetable chemical and mineral chemical. The first class is often spoken of in tanneries simply as the “vegetable” while the second is called “chemical” process. In the vegetable processes the tanning is accomplished by tannin, which is found in various barks and woods of trees and leaves of plants. In the so-called chemical processes the tanning is done with mineral salts and acids which produce an entirely different kind of leather from that procured by vegetable tanning.

There is also a method of tanning, or, more properly speaking, tawing, in which alum and salt are used. This process makes white leather that is used for many purposes; it is also colored and used in the manufacture of fine gloves. Leather is also made by tanning skins with oil. Chamois skins are made in this way.

The materials that are used to tan hides and skins act upon the hide fibers in such a way that the hides are rendered proof against decay and become pliable and strong. There are many vegetable tans; they are used for sole leather, upper leather, and colored leather for numerous purposes. The bark of hemlock trees is one of the principal tans. The woods and barks of oak, chestnut, and quebracho trees are often used. Palmetto roots yield a good tan. Large quantities of leather are treated with gambier and various other tanning materials that come from foreign countries. Sumac leaves, which are imported from Sicily, contain tannin that makes soft leather suitable for hat sweatbands, suspender trimmings, etc. Sumac is also obtained from the State of Virginia, but the foreign leaves contain more tannin and make better leather than the American.

To a large extent the so-called chemical processes have supplanted the vegetable processes, that is, old tan bark and sumac processes; but in some tanneries both methods are used on different kinds of skins.

In the old bark process the tan bark is ground coarse and is then treated in leaches with hot water until the tanning quality is drawn out. The liquor so obtained is used at various strengths as needed.

In the newer method the tan liquor is displaced by a solution of potassium bichromate, which produces its results with much less expenditure of time.

When the hides or skins are ready for the tanning process, they are put into a revolving drum, known as a “pinwheel,” or into a pit in which are revolving paddles, with a dilute solution of potassium dichromate or sodium dichromate, acidified with hydrochloric or sulphuric acid. If the pinwheel is employed, it is revolved for seven hours or longer; after which time the liquor is drawn off and replaced by an acidified solution of sodium thiosulphate or bisulphite, and then the revolution is continued several hours longer. If the pit is used, the skins are removed to another drum containing the second solution, and kept at rest or overturned for a like period.

In removing the skins from the pinwheel or vat, and in handling them after treatment with lime for the loosening of the hair, the hands and arms of the workmen are seriously injured, becoming raw if not protected by rubber gloves; even with gloves it is difficult to prevent injury, and in some establishments the workmen are relieved by the substitution of a single-bath process, in which the liquor is less harmful to the skin.

The hides are then removed from the pits, washed and brushed, followed by slow drying in the air. When partly dried, they are placed in a pile and covered until heating is induced. They are then dampened and rolled with brass rollers to give the leather solidity. Sole leather is oiled but little. Weight is increased by adding glucose and salt.

Various rapid processes of tanning have been devised in which the hides are suspended in strong liquors or are tanned in large revolving drums. It is claimed that this hastens the process, but the product has been criticized as lacking substance or being brittle.

Chrome tannage has been chiefly developed in this country during the last twenty years and is now in general use. It consists in throwing an insoluble chromium hydroxide or oxide on the fibers of a skin which has been impregnated with a soluble chromium salt—potassium bichromate. Other salts like basic chromium chloride, chromium chromate, and chromic alum are also used. The hydrochloric or sulphuric acid acts by setting free chromic acid.

After several hours, the skin shows a uniform yellow when cut through its thickest part. It is then drained and the skin worked in a solution of sodium bisulphite and mineral acid (to free sulphur dioxide). The chromic acid is absorbed by the fiber and later reduced by sulphur dioxide.

In the making of chrome black leather each tanner has his own method. Contrary to the general belief, there are many different methods of chrome tannage. No two tanneries employ just the same process.

Tanners of chrome leather seek to produce leather suitable for the particular demands made upon it by the peculiarities or characteristics of the varying seasons. Summer shoes require a cool, light leather; at other times a heavier tannage is essential, with some call for a practically waterproof product.

All leathers, whether vegetable-or chrome-tanned, must be “fat liquored.” That is to say, a certain amount of fatty material must be put into the skin in order that it may be mellow, workable, and serviceable. This is very essential in producing calf leather. Fat liquors usually contain oil and soap, which have been boiled in water and made into a thin liquor. The leather is put into a drum with the hot fat liquor; the drum is set in motion, and as it revolves the leather tumbles about in the drum and absorbs the oil and soap from the water. It is the fat liquor that makes the leather soft and strong.

Leather used in shoes is divided into two classes: sole leather and upper leather.

Sole leather is a heavy, solid, stiff leather and may be bent without cracking. It is the foundation of the shoe, and therefore should be of the best material. The hides of bulls and oxen yield the best leather for this purpose.

The hide that is tanned for sole leather is soaked for several days in a weak solution (which is gradually made stronger) of oak or hemlock tan made from the bark. Oak-tanned hide is preferred and may be known by its light color. A chemical change takes place in the fiber of the hide. This is a high-grade tannage, and is distinguished principally by its fine fibers and close, compact texture.

Oak sole leather, by reason of its tough character, and its close, fibrous texture, resists water and will wear well down before cracking. It is by many considered better than other leather for flexible-sole shoes, requiring waterproof qualities.

Sole leather is divided into three classes according to the tanning—oak, hemlock, and union.

Oak tanning is as follows: the hides are hung in pits containing weak or nearly spent liquors from a previous tanning, and agitated so as to take up tannin evenly. Strong liquor would harden the surface so as to prevent thorough penetration into the interior of the hides. After ten or twelve days, the hides are taken out and laid away in fresh tan and stronger liquor. This process is repeated as often as necessary for eight to ten months. At the end of this time the hide has absorbed all of the tannin which it will take up.

Hemlock tanning is similar to the oak tanning in process. The hemlock tan is a red shade. Hemlock produces a very hard and inflexible leather. It is modified by use of bleaching materials which are applied to the leather after being tanned. It is sold in sides without being trimmed, while the oak is sold in backs, with belly and head trimmed off.

Hemlock leather is used extensively and almost principally for men’s and boys’ stiff-soled, heavy shoes, where no flexibility is required or expected. Its principal desirable quality is its resistance to trituration, or being ground to a powder, and its use in men’s and boys’ pegged, nailed, or standard screw shoes is not in any way objectionable to the wearer. In fact, for this class of shoes, it is probably the best leather that can be used. But when hemlock is used in men’s and boys’ Goodyear welt shoes, where a flexible bottom is expected and required, it generally does not give good results. It cannot satisfactorily resist the constant flexing to which it is subjected, and after the sole is worn half through, the constant bending causes it to crack crosswise. On this account it becomes like a sieve, and has no power of resistance in water, and therefore it is not at all suited to flexible-bottomed shoes.

In “union-tanned” hides, both oak and hemlock are used and the result is a compromise in both color and quality. This tan was first used about fifty years ago. Twenty-five years ago the union leather tanners began to experiment with bleaching materials to avoid the use of oak bark, which was becoming scarce and high priced, and eventually developed a system of tanning union leather with hemlock or kindred tanning agents, excluding oak. The red color and the hard texture were modified by bleaching the leather to the desired color and texture. This produces leather which has not the fine, close tannage of genuine oak leather and at the same time lacks the compact, hard character of hemlock leather. Union leather produced in this manner is a sort of mongrel or hybrid leather, being neither oak nor hemlock. On account of its economy in cutting qualities, however, it is largely used in the manufacture of medium-priced shoes where a certain degree of flexibility is required in the sole. This is particularly true of women’s shoes.

Union leather is sold largely in backs and trimmed the same as oak, though not so closely.

Sole leather is also made nowadays by tanning the hides by the chrome or chemical process. This leather is very durable and pliable and is used on athletic and sporting shoes. It has a light green color and is much lighter in weight than the oak or hemlock leather.

Many kinds of hide are used for sole leather. This country does not produce nearly enough hides for the demand, and great quantities are imported from abroad, although most of the imported hides come from South America. Imported hides are divided into two general classes, dry hides and green-salted hides.

Dry hides are of two kinds, the dry “flint,” which are dried carefully after being taken from the animal and cured without salt. These generally make good leather, although if sunburnt, the leather is not strong. “Dry-salted hides” are salted and cured to a dry state. Dry hides of both kinds are used for hemlock leather only, although all hemlock leather is not made from dry hides.

Green-salted hides are used in making oak-tanned leather as well as hemlock, and those used by United States tanners come largely from domestic points; but there is a variable amount imported each year from abroad, principally from Europe and South America. Green-salted hides are of two general classes, those branded and those free of brands.

Cow and steer hides of the branded type are used by tanners of oak and union leather. Those not branded are used more largely for belting and upholstering leathers, a small part finding their way into hemlock leather.

Sole leather remnants, strictly speaking, include such a wide variety of items that it is difficult to cover them all. Few people, however, realize the big range of usefulness of this class of stock. While not exactly a by-product, remnants are often classed as such. Under the class of sole leather remnants are included sole leather offal, such as heads, bellies, shoulders, shanks, shins, men’s heeling, men’s half heeling, men’s and women’s three-and four-piece heeling, etc. Stock that cannot be used in the shoe business goes into the chemical and fertilizer trade, among other outlets. By a special acid process of burning this stock, ammonia is derived from it, which goes into fertilizer; and another by-product is sulphuric acid for the chemical trade. The amount of ammonia obtained is small, being about seven per cent of ammonia to a ton of sole leather scrap. This is mixed with fertilizer and sold mostly in the Southern States, and to a small extent in the West, there being a law in many of the Western States against the use of fertilizer made from leather products, on account of its low grade.