I'm not sure what the "original" color of the saddle was. It's a mess.
The original color derived from vegetable-tanning is pale brownish in color as those you see on handles of a Louis Vuitton bag also known as vachetta leathers.
This original tannin color behaves just like our skin – it tans darker under sunlight – so it gets naturally darker.
In contrast any aniline dyes that is applied will eventually fades under sunlight – so the aniline dyes becomes lighter while the natural color becomes darker.
This is where the mess-up is realized.
That is why you seldom see a blue color on these vegetable tanned leathers – always in the brown to black range.
If color is that important under sunlight, the option would to be used “hybrid translucent” dyestuff instead – only half of the dye color combination will fade off eventually while the micro-pigment stays on much longer.
Would it be possible to refinish it a darker brown/black?
Yes! Darker brown would be a better choice as it goes with the brown tone of the tannin color.
It should blend in nicely when the aniline browns slowly fades off while the original tannin brown slowly darkens, under sunlight exposure.
Would common leather dyes be able to withstand the wear a saddle is subjected to?
Dyes does not wear off by rubbing, it is anything that is on the surface of the leather that is subjected to wear.
A non-slip leather protection (Protection-D+) with its draggy-feel would be recommended for reduce friction wear.
Would the stripping process compromise the leather?
Stripping would also remove the original fatliquor as well – thus stiffen the leather when dry – the fatliquor need to be replenished thereafter to return the leather its suppleness from eventually cracking.
Leather is protein fiber and it is “amphoteric” – it can shift its ionic charge from cationic (+ve) to anionic (-ve) and vice versa depending on the products pH value that influence it – thus it is never safe to used any solution that has a pH value above its isoelectric point (the pH neutral of leather averaging at pH 4) in most cases which result in weakening the protein fiber (+ve) charges thus the beginning the denaturing the leather; manifest in many such side effects.
The dye migration may be due to such weakening of the (+ve) and (-ve) attraction, also known as hydrogen-bonding.
After stripping – the leather is once again hydrated at pH 3.3 to separate the stick together fiber of emptied fatliquor, recharging the protein fiber (+ve) – so that it hydrogen bonds with the (-ve) fatliquor of pH 5.0.
The choice of stripping would be first test out Degreaser-2.2 (pH 2.2) follows with Rinse-3.0 (pH 3.0); otherwise use Stripper-2.3 (pH 2.3) for best result.
Decide what you wish to do; I can walk you through the holistic process if you like.
Roger Koh
[email protected]