Crusting

During the crusting process the tanned hide is thinned, retanned and lubricated. There are a variety of processes that may or may not be used at this stage depending on the requirements of that batch of hides.

Most crusting processed begin with the re-wetting or wetting back of the tanned hides. After this in a process called ‘sammying’ 45 to 55% of the water is removed from the hide. The hide may then be split into one or more horizontal layers or thinned by the process of shaving, which removes the leather fibres.

During the entire process the pH values of the leather have to be optimally maintained in order to allow it to properly absorb the various chemical agents that are used. Once the pH levels are neutralised, the process of re-tanning is begun and the leather may or may not be dyed at this stage.

Once the desired colour is achieved a process called fatliquoring is used to fix wax and oils to the leather fibres. The leather may also be filled and stuffed to make it harder and heavier and to add oils and waxes between the fibres of the leather. The leather is then stripped to remove tannins which have been superficially attached to the hide.

If necessary the leather may go through a process of whitening in order to lighten the colour. During the fixation process, all the chemicals that have been previously used on the leather are either bonded within the leather or removed from it. During the setting process the flatness, grain and area of the leather is determined whilst the excess water is removed.

After this the leather is once again dried to reduce the water content to between 14-25%. After this the leather is conditioned, softened by separating the fibres and buffed to remove nap or grain defects.