The acid present in the chrome tanned leather can broadly be classified under the following heads:
- Free acid
- Protein bound acid.
- Acid present inside the co-ordination sphere of Cr-complex.
- Acid fixed with Cr-complex.
Causes:
- Acid hydrolysis of the skin protein.
- Leading ultimately to grain crackiness.
- Tearing up the leather.
Acid hydrolysis:
Generally acid hydrolysis provide some poor properties to leather. As they are-
- Poor tear resistance
- Poor overall strength.
- Grain crackiness.
Case hardening:
When limited pelt is added this solution the alkali reacts with the pelt & fixed both sides of the leather. Then the other tanning can't penetrate through the leather. This is known as case hardening.
Salt spue:
Salt spue are the salts in the leather becoming de-stabilised, when liquid is applied to the leather it causes an osmosis effect drawing the salt up to the surface.
Place a gentle heat over the white patch using a hairdryer if it doesn't disappear under heat it determines it may be salt spue (not Fat-spue).
Applying the more liquid to areas of salt spue will make the problem worse - as a test a apply wet/damp cloth to a small area around the white patch, if it more white spue appears it is a salt spue problem.
Salt spue can be difficult to stabilize, Someone can attempt to re-colour the area & hope it doesn't rear its ugly head again.
- Clean the area (don't soak the leather) with using the "Buffalo Mould Cleaner".
- Seal the are using " Gloss solvent sealant"
- Re-color & seal again.