The degreasing you practice is by the “dry method”.
The degreasing I practice is by the “leather safe tannery wet method”.
Bear in mind the safety, health and environment aspect of the work too (fire-risk, VOC-health risk, dusty environment)
Almost in every degreasing task, fatliquor need to be replenished as we are also inevitably extracting the natural leather fats and oils too (from the original tannery fatliquoring).
So it makes sense to take the “wet” route when re-fatliquoring is mandatory thereafter.
To take the “leather safe wet route”, anionic surfactant and pH value (3 - 5) is the key to degreasing success.
The surfactant works by penetrating, lubricating and suspending the foreign grease or oil, dislodging it loose by scudding and by the natural wicking of suspended residue to the surface.
These grease or oil is considered as “stuffing” grease or oils unlike the anionic charged fatliquor which is a “hydrogen bonding” oils and fats.
Even in extreme cases for nubuck and aniline degreasing, procedure is as follows: d’Oil4.4™ &/or d’Grease4.9™ > clean3.8™ > rinse3.0™.
Rinsing at low pH (3) plays an important role in its total degreasing of stuffing foreign grease.
Also observe the pH value of the above products.
These leather safe pH values do not cause the (tanning agents, fatliquors, dyes and preservatives) to break bonds with the protein fibers.
A pH above 5, vegetable tannins agents becomes progressively free and at pH 8 to 10 they are rinsed out as brown water.
When all liquid is scudded out during rinsing fatliquor is reintroduce into the leather structure.
At this point the protein leather fibers is preconditioned below the iso-electric point to be cationic (+) charged due to the pH 3.0 rinse.
Therefore, resulting the anionic (-) fatliquor 5.0± to bond very well with the cationic (+) protein leather fibrils.
This hydrogen bonding also displace and repel the non-polar foreign grease away from the protein fibers therefore floats by the wicking process onto the surface to be brush off especially in nubuck and suede.
This explains the boring degreasing phenomenal of the “leather safe wet method”.
It can only become logical when we try it out to see the end result!
This leather safe degreasing technology principle is based on the wet operation of a standard commercial tannery.
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Roger Koh
Leather Doctor® System