Leather processing moves raw hide through several distinct chemical stages before it becomes finished leather, each with its own chemistry.
Soaking and Liming
Hydrated lime is central to the liming stage, used to loosen hair and open up the fibre structure of the hide in preparation for tanning. Sodium sulphide is also commonly used alongside lime in unhairing.
See Hydrated Lime 90% SC and Sodium Sulphide.
Deliming and Bating
After liming, the hide needs deliming to reduce alkalinity before tanning agents can work effectively — ammonium salts and other mild acids are typically used for this step, bringing pH down in a controlled way rather than a sharp acid shock.
See Ammonium Chloride.
Tanning and Finishing
Formic acid is commonly used in the pickling stage ahead of tanning, adjusting pH to the range needed for tanning agents to penetrate the hide properly. Sodium bicarbonate is used at various neutralization steps in the process. Finishing stages often use dyes, fatliquors and finishing chemicals specific to the desired leather characteristics.
See Formic Acid.
Effluent Considerations
Tannery effluent is notably challenging to treat — high in dissolved solids, sulphide, and sometimes chromium depending on the tanning method used — and is subject to strict discharge norms in most jurisdictions given the environmental history of the industry. See our guide on ETP chemicals for general treatment chemistry, though tannery effluent often needs a more specialized treatment design than a general overview can cover.