Leather Tanning Agents

What is a leather tanning agent?

Leather tanning agents are chemical solutions that are used in the first step of the leather making process. To use a hide for a leather product it needs to be processed. This process is called the leather tanning process. By processing the hide with a leather tanning agent, it changes the chemistry inside the leather fibers to make it more difficult for the enzymes from bacteria and fungi to break them down – this makes the leather durable.

leather tanning: from hide to leather

Leather tanning is the process to prepare skins and hides for leather production.


What chemicals are used in leather tanning?

The most commonly used chemicals in leather tanning are based on either chrome, aldehyde, vegetables or zeolites.

Vegetable tanning agents

Vegetable tannins extracted chemicals are the earliest leather agents to be used in tanning. It uses extracts from wood, and nuts of trees and shrubs. Responsible suppliers ensure these come from a sustainable source. It usually takes longer to tan leather using vegetable tanning agents, but the result is a leather with a distinctive aesthetic and handle, which ages beautifully.

Its naming, as well as the tanning materials used, make it seem as if vegetable tanned leather is more ‘eco-friendly’. However, we need to take the entire balance across the whole process into account, to make a more meaningful comparison with other methods. For example, vegetable tanning uses a few times the amount of tannins than for chrome-tanned leathers. The effluent produced also requires more treatment before it can be discharged. However, it has the benefit of using natural, sustainable and renewable raw materials.

Chrome tanning agents

About 75% of leather made today is tanned with chrome tanning agents. The process uses trivalent chromium (Cr III), which is a safe substance. Chrome tanning produces consistent leathers that can be used or worn, year after year, without any loss of properties. It is sometimes suggested that hexavalent chrome, or chromium VI (Cr VI) is used for tanning leather, and that it is carcinogenic. Chromium VI is not used in the manufacturing of leather. The process of chrome tanning is constantly being upgraded, as its uptake is improved, less of it needs to be used, there is comprehensive recycling, reduced water consumption and careful management of waste. The chemicals used in chrome tanning do put a strain on the environment.

Chrome-free / aldehyde tanning agents

There is a number of other tanning agents, known by different labels. They are usually grouped and referred to as ‘chrome-free’. Chrome-free leathers are usually made for a specialized performance requirement, or often specified for automotive use. The most common is aldehyde tanning, which utilizes glutaraldehyde. Leathers made with this tanning agent require relatively more chemicals after tanning, to improve the leather properties. For this reason, the effluent of a glutaraldehyde based chrome-free process will require additional treatment, before it can be discharged.

Zeology: zeolite-based tanning agent

A new innovation in leather tanning chemicals is the use of zeolites. Zeolites have a unique property in that they can absorb or release water, depending on the temperature. Water absorption is an important part of leather comfort, and a tannage that allows water absorption (without swelling) is a desirable characteristic.Mind you, that zeolites on itself are not suitable as a leather tanning agent. Zeology, with a modified zeolite (patented), is the only zeolite-based tanning agent that is developed for optimal leather performance on any substrate with low environmental impact and unmatched production consistency. Zeology is chrome-free, aldehyde-free and heavy metal-free and does not compromise on leather performance.