How does neutralization influence the leather quality?
Neutralization is actually the de-acidification process prior to retannage and dyeing of leather. The chrome tanned leathers (also other mineral salt tanned leathers) separate acid, as a result of olation during intermediate storage before further processing. It is absolutely necessary to remove this free acid as it disturbs the subsequent processes. If neutralisation is not performed colour stains by dyes and overloading of grain by tanning and fatliquoring agents occur resulting in poor quality of leather. Degree of de-acidification depends on desired quality of the final leather. Commonly used neutralizing agents are sodium/ammonium bicarbonate sodium thiosulphate. Special mixtures are often used for even, penetrative neutralization without risk of over-neutralization. Syntans with neutralizing effects are also used with beneficial effect.
