How is leather made?
Previously, we have specifically spoken about Vegetable and Chrome tanning and the differences between them. However in both cases, this is only one step of producing leather. Some of the additional steps are shared between both methods however, we will focus on how Vegetable tanned leathers are made as that is mostly what we use and what we love.
Skinning and Curing
Curing is the first step after skinning an animal is to preserve the leather, as there is a large amount of time usually between butchering the animal and the tannery receiving the hide. Salt is applied which prevents bacteria from growing and ruining the hides during this time and the salt is removed once it is ready to process into leather at the Tannery.
Most hides are a byproduct of the meat industry and any Tannery part of Tuscany's Pelle Vegetable Tanned Leather Consortium are required to only source hides from the meat industry. We do not strictly use Italian leather, however this is a principle the Tanneries we work with in Japan do abide by.
Lime Soaking
This step is used to swell the leather up and loosen the top layer of leather such that hair follicles and fat deposits can be removed from the leather. Lime also opens up the skin structure to allow the tannins to better bind with the fibers of the leather in future steps. In ancient times ash and water was used.
De-hairing
Craftsmen have to manually remove hair and fat with long curved knives.
De-liming
Lime is extremely basic so the leather must be returned to neutral pH before the process can continue.
Tanning
This is the crucial and time consuming step. Tree matter is mulched up and fed into pits of water which are constantly agitated, where the hides will sit for a period of months to even over a year. Some tanneries use barrels or rotating vats to tan the leather and it can speed up the process. The tannins from the plant matter are absorbed by the hides and this protects the leather. See our article on Vegetable tanning to learn a bit more.
Drying
The hides are removed after tanning and are left to dry out. In ancient times they were stretched on beams but now they are wrung out with pressing machines and slicked against glass. This step varies from tannery to tannery.
Hot stuffing
Not all leather tannages have this step but any leather with waxes in it will be stuffed. These leathers are typically known as pull up due to the colour variation seen when the leather is flexed or pressed which is caused when the waxes move around.
Dying
The next step is to apply colour dyes to the leather. Some leathers are dyed right through to the split and others are only surface dyed. Some leathers are left undyed so that they may be dyed later as the leatherworker chooses.
Finishing
This is the step of applying some sort of protective layer on the top of the leather to prevent it from scratching and absorbing water and discolouring. Typically pigments are used and the amount of finishing can vary. Leather can be finished but much of the grain and hair pores can remain visible or it can be thick and they are covered up. This step varies from tannery to tannery and from leather tannage. This is what makes vegetable tanned leather so wonderful as there is a huge variety of ways to finish leather to achieve a large variety of effects. For instance, anline leather is leather which is specifically left with no finishing, though this word is often used incorrectly or is used as an outright lie. Leather may be tumbled to soften and break in the leather and pronounce the grain or it may be embossed with a fake grain pattern or really any other pattern, such as false crocodile scales. Or the leather may be sanded to create a nubuck or the revere side used to produce a suede.