We are excited to partner with Maker’s Row to bring you this four-part series. Over the next eight weeks, we’ll cover leather basics and the journey of a hide, we’ll dive deep into the tanning process and discuss what you should look for when sourcing leather for your projects to make you a more informed buyer.
This post covers the leather basics. We’ll take you through the many facets of leather making, from a brief history of tanning to demystifying those tricky industry terms.
Leather has been around for millennia. Developed by some of the earliest civilizations on the planet, humanity has been able to utilize animal hides to produce leather for almost any industry or application imaginable: from upholstery, apparel, footwear, and accessories, to applications in the military, industrial factories, musical instruments, and even sports. Thanks to the flexibility of the tanning process, leather remains a versatile material.
What is leather?
Most people understand that leather is made from animal hides. But what is leather? How does it transform from a biodegradable material into something that can last hundreds of years without breaking down?
Simply put, leather is an animal skin that has undergone the process of tanning. Nearly any animal with a suitable hide can be turned into leather through tanning: goat, cow, emu, alligator, stingray, and even the smallest fish and frog.
What is tanning?
Tanning is a method of using specific chemicals derived from minerals, plant matter, or oils that fix to the fibers of a skin to prevent bacteria and atmospheric conditions from breaking it down. Most likely this process was discovered by accident as discarded hides sat in waste matter or were exposed to pools of minerals.
Once people realized what was happening they began to purposefully recreate the process. The earliest tanning methods utilized oils derived from the animal itself, certain types of local tree bark or leaves, or naturally occurring minerals. Later formulae refined the process, concentrating the tannins from trees (the same chemical from which tanning derives its name!), synthetically creating oils, and purifying chrome and aluminum salts to yield precise tanning solutions.
Today, over 90% of leather produced in the world is chrome tanned, a tanning process that uses chrome salts. China, Southeast Asia, India, Brazil, Argentina, and Mexico lead the world in chrome tanned leather production. Chrome tannages can serve as a base for re-tans, like a vegetable or syn-tan (short for synthetic tan, a process that utilizes organic chemicals). Buyers often favor chrome-tanned leather for its relatively low cost, production speed, and volume. However, the process can have environmental consequences if the wastewater is not managed properly.
The remaining 10% of leather production is comprised of either vegetable or, rarely, oil tanning. Most vegetable tannages utilize tannins extracted from the bark, wood, and leaves of certain trees, like oak. Oil tanning traditionally incorporates cod liver oil but today most of the oils are synthetic. These two processes are more specialized, and tend to create a higher cost to the buyer but are generally more environmentally friendly.
Even after being tanned, leather remains a surprisingly rough material. In this pure, unfinished form, leather is called crust: it’s uneven in thickness, a little gritty in texture, with varying degrees of moisture from too dry to too oily. The tanning process directly influences the feel, also called the body. Leather body ranges from extraordinarily dense and stiff with the ability to stop knives, to the spongy, supple leather suitable for the softest pair of gloves. But there are certain things that can’t be achieved with tanning alone; this is where leather finishing comes in.
What is leather finishing?
It’s the leather finisher’s task to hone the look and feel of the material before it’s sent off to leather workers for finished goods. Finishers can exist both within and independent of a tannery. Leather finishing encompasses all of the steps that refine crust leather, such as splitting skins to an even thickness, dying them the desired color, oiling or waxing, sueding, milling, coating, and embossing. These applications can be combined in a multitude of ways to give designers, manufacturers, and craftspeople a slew of choices when looking for specific textures, colors, and hand (surface feel) for their finished product.
Stay tuned for our next post where we’ll look into the true raw material: the hides.