The majority of leather produced nowadays is tanned using chrome process tanning. Chrome tanned leather tends to be softer and more pliable than vegetable tanned leather. The tanning process is similar to that used in Vegetable Tanning but additional processes of retanning, dyeing and fatliquoring are used to create more consistent feel and colour in the leather.
Chrome tanning actually works by soaking the leather in a bath of Chromium Salt/Sulfate. This creates a base ‘tanned’ skin that is now ready to be finished and coloured.
Because the chrome tanning process is acidic, the leather is first neutralized with sodium bicarbonate and sodium formate or acetate, after which it is retanned with synthetic tanning agents called syntans, resins and natural tannins, which impart the desired properties to the leather being made. The leather is then dyed to the required shade and finally "fatliquored“ - natural and synthetic oils are taken up by the leather to replace the natural greases removed in the preceding processes, so that the fibres will be lubricated when the leather is dried.
When you see a mock crocodile leather this will have been made using an embossing process. Embossing is a process that heat presses an artificial grain pattern into the leather. This leather still starts as a full grain leather although the grain of the leather will normally be hidden one the emboss has been applied. The tanning process will normally be chrome tanning with the pigment or colour sprayed onto the leather surface.
After dying and milling, a pigment coat is sprayed or rolled onto the hide surface. The coating is very light and is generally just enough to produce a uniform surface color. The added color pigment helps to control shade variations from hide to hide and provides a greater degree of protection from fading. Finally, a top coat of synthetic, transparent resin is applied as a protective coating in either a high gloss or matte finish.
Two tone leathers
This is simply a leather that once dyed will have an additional coating of dye applied to it – usually this would be applied by spray. This allows us to polish the surface of the leather to gradually reveal the colour of the leather below, achieving a two tone finish.