Yellowing

Pickle - if pickled stock is stored for long periods the grain may become yellowish in colour. This is caused by hydrolysis from using too much acid in the pickle and is accompanied by a loss of fibre strength.

Finished leather - yellowing of white or pastel shade of leather may occur. The cause could be oxidation of oils used in the fat liquoring process, plasticisers in the finish discolouring or use of non-lightfast dyestuffs.

Yellowing on heat

Yellowing of finishes due to heat depends on the products used causing oxidation or ageing of fatty substances, plasticisers or nitrocellulose lacquers. Especially a problem of white and pale leathers.

Yield

Product of a reaction or process as in chemical reactions or leather processing. It usually is the amount (as area yield or weight yield) of leather produced from a given amount of starting material.