Primer
From www.leather-dictionary.com - The Leather Dictionary
In the tannery, primers are used to promote adhesion of porous aniline leather and the colour layers to be applied. The primer prevents the pigment colour from being "absorbed" by the leather and its adhesive effect ensures the colour adheres to the surface. If excess colour is absorbed by the leather, it would get stiffer and plastic like due to stiffer binders in the leather colour. Primer prevents this and ensures the colour runs more evenly on the leather by "covering" extremely porous areas.
Structure of the leather colouring and finish.
Additional information
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