Synthetic tanning agents
Tanning agents that are produced synthetically, i.e., not found naturally in the environment, belong to this category. Formaldehyde, glutaraldehyde, phenols, uric acid derivatives and acrylates have a particularly effective tanning action. As a rule, synthetic tanning agents are not used as the sole tanning agents, but produce very interesting results in conjunction with vegetable or chrome tanning agents. This is known as combination tanning. At one time, it was not possible, for instance, to produce soft leathers with a vegetable tanning agent alone. Today, this is easily achieved by a synthetic pre-tanning process.