Just curious about the acidity problems some folks have...does anybody know what a typical ph is for a batch of fresh brewed vinegar dye? And then what the ph is of leather freshly dyed with the stuff...? And maybe even what the ph of the leather was, or was supposed to be before it was dyed?
I am not sure that a weak organic acid, such as vinegar, is the problem with leather cracking and flaking in use.
Some years back it was claimed that the old use of acid based leather dyes, such as nitrate of iron, destroyed the leather. What came out of that was the fact that years ago most homes had sulfur fumes in the building from the heating systems burning fuels such as coal. When the oxides of sulfur, in the air, got into the leather it formed sulfuric acid which will destroy leather.
When I was doing pouches some years back I noticed that the leather I was buying had no oils in the leather. The tech books on the leather industry went into a process they called "stuffing" the leather. The final step in the tanning process was to place the hides in a rotating barrel and add what is described as a non-oxidizing oil. Large quantities of menhaden fish oil had been used for this purpose. The oil would act as an "internal lubricant" within the leather giving it flexibility. If the leather is not "stuffed" it tends to be brittle and the fiber structure begins to break down and the leather simply falls apart.
The oil used to "stuff" the leather also limits the amount of water the leather picks up from the air. The oil acting something like a waterproofing agent. Leather is extremely porous and hygroscopic.
So the breakdown of the vinegar dyed leather may be more a point of not being "stuffed" rather than any chemical attack by residual acetic acid in the leather left over from dyeing.
E. Ogre
