Leather Processing Through the Years
Not many years ago, a leather interior in a car was an expensive luxury. It didn’t come on a vehicle except as an expensive option. This was primarily due to the material costs alone. It doesn’t really take any more time to upholster a leather seat vs a vinyl seat, it just that leather is far more expensive than sheet of vinyl. The reason why is simply manufacturing costs; there are many, labor-intensive steps needed to make high quality leather. Let’s take a closer look.
The history of leather processing actually goes back thousands of years. Primitive humans needed some sort of clothing and there weren’t any fabrics back then. The substitute, of course, was animal pelts.
Unfortunately these pelts probably didn’t last very long. After all, this is a natural product that would eventually decompose. However, some clever group discovered that when pelts were soaked with certain plants, they would be preserved. In addition, certain fats served as leather conditioners to keep the leather flexible and soft as it aged. Thus began the trade of leather conditioning.
Fast forward to the 18th century and leather processing had become an old respected trade. The process was much improved over the early days but it still took a long time; typically about a year before a hide was delivered as finished leather to the end user.
Today, most leather comes from the skins of cattle, sheep and calves. Central Avenue, Chrysler of Yonkers, NY , a full-service Chrysler, Dodge, Jeep, Ram dealer, tells us that the leather in all Porsches comes from a specific type of cattle that are raised in temperate climate zones.
The leather harvesting process starts with the process of carefully removing the hides after the animal is killed. After the hide has been removed, it is “fleshed” removing any remaining meat, tissue or fat. Freshly fleshed hides are then shipped in refrigerated trucks to tanneries for immediate processing into leather. In some cases, the fleshed hides are cured or preserved by immersion in brine for 12 hours. After curing, the hides can be stored for several months without damage and can be shipped to tanneries throughout the world without needing refridgeration.
At the leather tannery, hair is removed by chemical means by using a solution of lime and sodium sulphide. The hides are then neutralized with acids and treated with special enzymes to increase softness. The next operation, pickling, the hides are soaked in a solution of water, salt and sulfuric acid.
The last step in turning hides and skins into leather is the tanning process. There are several methods of tanning but the most common is chrome tanning. The process begins in rotating drums with a bath containing trivalent chrome for some 8 hours. Once this has finished the chrome is fixed by adding sodium carbonate or bicarbonate.
Final finishing consists of placing a series of coatings on the surface of the leather. These coatings are designed to protect the leather and make it pleasing to the eye. Some finishing processes apply plastics such as acrylic and urethane resins to the surface of the leather. Others coat it with vinyl, wax, or nitrocellulose. To make the surface of the leather look good, leather is often embossed with a pattern.
The last step, of course, is upholstery. After the leather sheets are finished, they are shipped to upholstery companies that use the leather to construct automotive seats and other leather-covered interior pieces.
Previous articleClearing Cloudy Headlight Lenses