Cowhide, antelope hide, lambskin, and buckskin are most commonly used to make leather jackets.
Leather is a material made from the hide or skin of animals that has been chemically treated. The term "hide" generally refers to the skin of larger animals, such as cows, while the term "skin" is used for smaller animals, such as calves. The term hide is used in this article for all animals.
Since early history, humans have used leather to make clothing. They discovered that after using hunted animals for food, they could wear the hides as protection against cold and bad weather. However, they did not know how to preserve the hides, so that the hides eventually rotted away. Over time, people learned that stretching the hides over frames and then drying them in the sun made them last longer. Later, people learned to clean the animal cells from the hides by scraping them with stones. This method removed the bacteria that caused decay. People also found that hides could be dried with smoke and softened by rubbing with the brains and fats of the animal. Today's leather jackets continue to possess the durability and flexibility that early humans found useful. The timelessness of leather jackets is evident in their popularity among people of all ages all over the world.
Tannin to the rescue
Evidence indicates that, thousands of years ago, ancient civilizations, including Egypt, India, and China, used a substance called tannin (or tannic acid) found in tree bark to convert animal hides into leather. This process not only preserved the hides but also gave them softness and flexibility. The ancient Hebrews first used the tannin from oak bark, which became the popular source of tannin because it grew in many places. The Greeks discovered that tannin could also be found in walnuts, pomegranate peels, and the bark of conifer trees.
Through the ages
The ancient Phoenicians used leather pipes to transport water from storage containers to their homes. Soldiers of the Roman Empire wore leather shoes and tunics, as well as breastplates and shields. During the Middle Ages (476 C.E.–1453 C.E.), the Moors introduced the softer cordovan leather (named after Córdoba, Spain), which was made from goatskin. Between the 1300s and the 1600s, several guilds (trade associations) within the leather industry had been formed all over Europe. In Central and South America, the Mayan, Incan, and Aztec cultures also used leather, as did the American Indians, who made garments from buckskin, doeskin, and buffalo hide. The American Indians used fish oils for tanning and animal brains and fats for softening hides in much the same manner done by the ancient people.
The Industrial Revolution, which began in England during the second half of the eighteenth century and which swept through the United States during the nineteenth century, resulted in the mechanization of the leather industry. In 1809, Samuel Parker (1779–1866) of Massachusetts invented a machine that split hides to any desired thickness. In the past, if a certain thickness was required, a worker called a currier trimmed the leather, resulting in plenty of wasted material. In 1884, Augustus Schultz, a New York City chemist, developed a tanning method using chromium salts. This method not only cut the tanning process from weeks or months to just hours or days but also made the leather more water-resistant.
Keeping the old, adding the new
Over the years, the manufacture of leather has not changed much. Chrome tanning is the method most used today; however, vegetable tanning is still performed. Although some countries still manufacture leather manually, in the United States computerized programs control machine operations, including the measurement and mixing of chemicals. Interestingly, Parker's splitting machine is still in use.
Cowhide, antelope hide, lambskin, and buckskin (from male deer and sheep) are most commonly used to make leather jackets. At the meat processing plant, the hide is removed from the animal. (Today, as in the past, animal hides are by-products of the meat industry. Ranchers do not kill cattle just for their hides.) It is immediately refrigerated, salted, or packed in barrels of brine (salt water) to keep it from decomposing. The hide is then sent to the tannery, where it undergoes a series of processes to permanently preserve (prevent decay) and soften it.
Sewing materials, which are typically purchased from outside vendors, are stored in the garment factory. These materials include thread, lining, seam tape, buttons, snaps, and zippers.
The Preparation Process
Before the raw hide can be treated chemically to make it into leather, it has to undergo a thorough cleaning and dehairing. These steps ensure that any decay-causing bacteria are completely destroyed.
Trimming and cleaning
1 The hides are trimmed and sorted according to size, weight, and thickness. They are soaked in revolving drums filled with water, detergents, and bactericides (substances that destroy microorganisms). This soaking process removes salt, dirt, and blood, as well as proteins that could encourage the growth of bacteria. Hair is removed using chemical sprays or lime solutions.
2 Excess hair is further scraped off by scudding, a process that removes scuds, or the remaining unwanted hair, dirt, and other substances left in the hair follicle after dehairing. Scudding is done by hand with dull knives or by a machine that squeezes out the scuds. The hides are again washed to remove any remaining chemicals.
3 Next, the hides are soaked in an acid solution. Then, they undergo bating, a process in which they are treated with enzymes, or substances that hasten the breakdown of nonfibrous proteins in the hides. Bating serves to strengthen the collagens (fibrous proteins) in the hide by getting rid of the nonfibrous proteins. This results in soft, flexible hides. Finally, the hides are pickled with salt and sulfuric acid for more softening and cleaning.
4 Tanning refers to the process by which hides are preserved and converted into leather. The word is derived from tannin (also called tannic acid), a plant material that bonds the collagen in the dermis of a hide by ridding it of its water content.
One of three methods of tanning may be used. Vegetable tanning consists of soaking the hides in progressively stronger tannic acid solutions for several weeks or months. This method produces a firm leather.
In mineral tanning, the hides are typically soaked in water filled with chromium salt. Since chromium salt is the most frequently used tanning agent, the terms mineral tanning and chrome tanning are often used interchangeably. Aluminum or zirconium salt may also be used. The process, which takes just a few hours or days, produces leather that is softer and more flexible than that made by vegetable tanning.
Oil tanning resembles the ancient methods and uses fish oil that is sprayed onto the hide. The oil is then pounded into the hide. This method was originally used to make leather out of the hide of the chamois, a small antelope native to the mountainous areas of Europe and Asia. Today, chamois leather refers to the soft, absorbent leather made from the inner side of a sheepskin. It is generally used for polishing and washing.
Washing and drying
5 After tanning, the hides are washed again and wrung out thoroughly to remove all moisture. The hides are passed under a band knife, which cuts the hides horizontally to a uniform thickness. Next, the hides are transported by a conveyor belt to drying tunnels. To prevent shrinkage during drying, the hides are stretched on frames. They are sprayed with water and soap and allowed to hang for a period of time so that the stiffness caused by the drying does not set in.
6 The hides are placed in machines that loosen up the fibers, making the leather more flexible. Finally, the hides are hung in vacuum-drying cabinets.
7 The completely dried hides are buffed with abrasive cylinders. Buffing, a process comparable to sandpapering, is done to remove some surface imperfections. The hides may also be sueded by passing the flesh side of the hides under high-speed emery wheels. This process raises the fibers to produce a velvet nap (fuzzy) effect.
8 The final step is called finishing, or the application of a thin coating on the leather surface to preserve its appearance. Some are glazed for a polished look, while others are dyed, or colored. After the finishing process, the leather pieces are sent to garment factories.
The Manufacturing Process
Leather garments are still considered luxury items, and some consumers are willing to pay more for those that are hand-constructed by skilled craftspeople. The following steps are those used in factory mass production.
THE ONE IN THE MIDDLE
An animal hide consists of three layers—the epidermis, or outer layer; the dermis, or middle layer; and a fatty layer. The dermis, also called corium, is the thick layer that is processed to obtain leather. The collagen, or fibrous protein, in the corium gives leather its strength and flexibility.
1 Garment manufacturers typically employ designers to create patterns from which leather jackets are made. Computerized machines grade the designs based on government tables of body measurements. These tables assign sizes based on body weight and height. The computer then produces patterns using the original design. A variety of pattern sizes are made.
2 The tanned leather is placed on moving tables called spreaders. It is preferable to cut leather one layer at a time. A tissue-paper pattern may be placed on top of the leather, or a pattern is marked on the leather with tailor's chalk. The spreader works like a conveyor belt, moving the leather to the cutting machine. The latest technology uses a computerized laser beam system that vaporizes fabric seams instead of cutting them. The system's high-speed action is ideal for cutting single layers of leather.
3 Lining material for the jacket is cut using the same method. Multiple layers of lining material may be cut at one time.
4 The jacket sections are put together. First, the patch pockets are sewn onto the side pieces. The side pieces are then stitched to the back section. Side pockets are sewn in at the same time that the sides are attached to the back section. The sleeve underseams are sewn together, and then the sleeves are attached to the armholes. The linings are generally assembled before being sewn into the jacket. Buttonholes and finishing pieces, including collars, cuffs, buttonholes, buttons, and zippers, are attached to the jacket according to the design specifications.
The jacket sections and finishing pieces are moved along a production line that uses automatic sewing machines capable of sewing as many as eight thousand stitches a minute. The jacket sections are assembled following sequential steps. For example, a machine sews a cuff to a sleeve, which is then moved to another machine where it is attached to the jacket armhole.
Two machines may work on the jacket at the same time. For example, one machine attaches buttons to the front, while a second machine is adding the collar.
Each step in the jacket assembly is preprogrammed—from setting thread and needle positions to removing the finished product. Devices in the machine automatically knot and cut threads after each seam is sewn. Excess threads are removed to trash bins by compressed air.
Although each step of assembling the jacket has been preprogrammed, operators regulate each sewing machine with the help of a presser-foot or a control panel. An operator can stop production to make adjustments, such as to change a broken needle.
Shaping and pressing
5 Finally, different pressing processes involving heat application, steaming, and blocking are performed. To give the jacket a distinctive shape, such as a blazer style or a bomber style, buck presses are used. These presses are equipped with controls and gauges that regulate the amount of steam and pressure. Curved blocks are placed around the collars and cuffs, then heated to achieve a curved effect.
6 Each jacket is inspected by hand before it leaves the factory. The jackets are encased in plastic bags, packed into cartons, and shipped to the sellers.
The tanning process has to be thorough so that the completed product is not only soft and flexible but also free of bacteria-causing proteins that could result in decay. Jacket manufacturers inspect each shipment of leather for marks, tears, stains, and imperfections.
The automatic sewing machines used today are self-correcting. The machines have a display panel like a computer screen. A program within the machine indicates on the display panel any problem in operation, as well as the solution to that problem. The machines have sophisticated lubricating systems (to keep the machines well oiled and working properly), which ensure finished products that are consistently of good quality.
According to experts, to check if a leather jacket has been dyed properly, rub it with a tissue. Very little dye, if any, should come off. This means that the leather was immersed in a dyebath that penetrated the leather, instead of just being superficially sprayed or painted.
Despite the high cost of leather, leather jackets continue to be in demand. The new styles and colors have come a long way from the black bike jackets that first became fashionable during World War I (1914–18). Manufacturers have come out with jackets of all colors, including pastels. Lightweight leather jackets for not-so-cold-weather wear and styles that can be worn for different occasions have become very popular. Some manufacturers have produced leather jackets embossed to look like the skins of snakes and alligators. The raised texture characteristic of these more exotic skins is created by heavy pressure of a machine.
- The fibrous protein that makes up most of the dermis, or middle layer, of animal hides.
- The thick, middle layer of an animal hide that is processed to obtain leather. Also called corium.
- In medieval times, an association of people of the same trade formed for their mutual aid and protection and the setting of standards and regulations.
- hoof-and-mouth disease:
- An infectious viral disease that affects such animals as cattle, sheep, and deer. The animals develop sores in their bodies and become very weak. Some young animals die from the disease.
- mad cow disease:
- A fatal brain disease that causes animals to stagger and behave strangely.
- Using a machine to do work previously done by humans or animals.
- production line:
- A sequence of machines in a factory through which products pass until they are completely assembled.
- The process of raising the fibers on the skin side of a hide to give a velvet nap effect.
- A place where animal skins and hides are converted into leather.
- A chemical process by which animal hides and skins are converted into leather.
For More Information
Scrivano, Sandy. Sewing with Leather and Suede: A Home Sewer's Guide: Tips, Techniques, Inspirations. Asheville, NC: Lark Books, 1998.
Donohue, Amy. "Jacket Requirements." Men's Health. (October 1997): pp.100-101.
Joyner, Valerie. "The Leather Channel: Warm Temperatures May Be Taking a Toll on Sales, but Outerwear Makers Say Leather Is Saving the Day." Daily News Record. (December 17, 2001): p. 145S.
Medintz, Scott. "Leather Report: When a Jacket's Beauty Is Skin Deep." Money. (October 1998): pp. 222-223.