All About Leather Tanning

We know how much our customers love their leather jackets, bags, wallets, gloves, and other accessories. Leather feels great, smells like nothing else, and makes a unique fashion statement. In order to understand true high quality from low quality leather, it's important to understand the process of leather tanning.

What Does 'Tanning' Mean?

Tanning is the word used to describe the process of converting raw animal skins and hides into leather. The tanning process takes place in a tannery. Tanning changes a hide's protein structure to stop the skin from decomposing so it can be made into a stable material. The aim is to be able to resist water, be supple, and remain durable.

The way in which tanning is accomplished is by using special tanning agents, some of which are composed of a plant product called tannin, hence the name of the process. Also used in the leather tanning process are fish or animal oils and chromium salts.

There are two basic types of tanning leather: chrome tanning and vegetable tanning.

Chrome Tanning

This tanning method soaks the leather in metal chromium solution. This enables the leather to become water resistant while still feeling very soft and having the ability to be dyed in a wide choice of colors that remain vibrant over time. Chrome tanning also lets the leather tolerate heat well.

Vegetable Tanning

Natural materials are used during vegetable tanning processes, when the skins are soaked in vegetable liquors. This process results in leather that is thick yet pliable. One of the issues with vegetable tanning is that the resulting products don't withstand heat very well, resulting in cracking or shrinkage if overheated. Vegetable tanned leathers, when done correctly, are highly prized for their quality.

Combination Tanning

There is a tanning technique that uses both vegetable and chrome elements to produce soft, durable leathers that are also flexible and thick, incorporating the best of both worlds, with less of a chemical impact on the environment and helping those of you who have chemical sensitivities.

Before The Process Begins

The entire leather tanning process involves a number of different steps and stages. There are quite a few things that must be done prior to the actual tanning stage. These steps include:

  • Curing the raw hides or skins to preserve them by salting, chilling, freezing or using chemical methods
  • Soaking the skins to let them reabsorb lost water
  • Removing the wool, epidermis, hair, and tissue
  • Neutralizing the pelt alkali by deliming 
  • Pickling to preserve the hides for storage or transport
  • Degreasing the skins with water or solvents

Splitting Leather

Now that the animal skins have been readied for tanning, the tannery will opt for using a chrome, vegetable or other non-traditional tanning methods. After the tanning is done, a machine is used to split the leather into one or two horizontal layers. The choice when it comes to splitting depends upon the final product that is desired. For example, a layer that lacks a grain surface can be turned into suede.

Shaving

A cylinder machine smooths the skin's surface on its non-grain side in order to create a more uniform thickness to the piece.

Dyeing

When you look for that perfect leather jacket, you take note of the color of the leather in addition to its overall style and material. Leather can be dyed into a variety of colors, either on its surface or throughout its layers, as with suede leathers. The material is placed in specialized drums to achieve consistently uniform dyeing results.

Stuffing

We all love leather jacks and accessories that are rich, flexible, and soft to the touch. This is why different fats and oils are introduced into the fibers of the leather. Without this particular step, called fatliquoring, leather jackets would be hard and unbendable as they dry out.

Drying

After all of the water and oils that have been added to the leather during this tanning process, the leather now needs to be dried out. The material is dried so that about 10-20% of it is still water content for lasting flexibility. The leather can be dried by tumbling it in a rotating drum after it's been massaged to separate the fibers. Other methods of drying include exposure the layers to air or by vacuuming out excess liquid. Uniformity in drying is important, and it necessitates constant timing and inspection.

Finishing Up

The leather skins or hides have gone through the entire tanning process. What's next? The final stage is appropriately termed the finishing stage. The mission of the finishing stage is to ensure the coloring is even throughout the leather, grain defects are eliminated, excess gloss is limited, and a protective surface is added to combat water, chemicals, and abrasions from altering the material.

The leather will be polished for a shiny effect, ironed for smoothness, and undergo other design effects depending upon the desired final product.

The leather tanning process is one of our oldest human activities. At first, skins taken from hunted animals were used as weather-protective clothing. Today, the production of leather goods is considered a skill, developed by experienced craftsmen around the world.