Mechanical process after tanning

Horsing up (ageing) and sammying
An extremely important point is ageing time and moisture content of chrome tanned leathers before neutralization in storage. More important still is the moisture content just before shaving because too much water or too little would produce less than optimal cutting conditions in shaving. If there is variation in moisture just before neutralization, all other chemicals will also be uneven quality due to different percentage of base weight on shaved weight.
The following points should not be overlooked
1. Proper horsing up does not produce holding wrinkles but allows for a very smooth grain side bottom, this being important for avoidance of oxidation of grain edge during ageing.
2. Ageing should be done for a minimum of 3 days or if possible for one week per lot.
3. Sammying for shaving in general moisture content should be 35 – 40 % the condition should be decided by the operator, as it becomes slightly white after sammying. The same applies to splitting before the hide is shaved. Control of sammying can be done by weighing packs before and after to see how much water has been removed. A further most important point is that the stock should never be allowed to dry out before neutralization as wetting back will be extremely difficult.
Splitting and shaving
Most splitting in Pakistan is done after the chrome tanning stage. In the Punjab a few tanneries are doing lined white splits, but apart from this they are hardly seen here. The moisture content before blue splitting and shaving is an extremely important factor, but in many places removal of water is not mechanized. Many tanneries are sammying by hanging or by spreading on the ground in the sun. Spreading gives more uniform evaporation the hanging but the same conditions for evaporation, time to time leather to leather. Part to part of leather are important to maintain and this is sammying is done on concrete on the ground.
These small stones and dirt particles will cause not only spot on the leather but also possible damage to parts of the splitting machine and shaving machine. Therefore the ground must be cleaned before leather is spread on it. And the above condition for evaporation carefully watched and controlled by sorting the skin into small and large heavy and light. Also control of the condition of the splitting and shaving machines must be maintained and marking by the operators on the tail or other parts of the skin should be watched. The moisture content after shaving must be kept the same before neutralization by completely covering the stock with a plastic cover. If they become too dry, then not only would the basic weight of the chemicals be different but the stock would not uniformly effected by wetting back.
After shaving stock should never be kept too long and certainly not more than overnight. If the leather is pressed too hard during shaving, wetting back will be difficult. As far as possible sorting for the next stages best done after shaving.