Best ways to avoid black "inking" stains on vegetable tanned leather?

[Mallethead]

How do you avoid black stains from metal fittings? As far as I understand, these are caused by metals reacting with tannins in the leather.

[JD62]

These stains come from the tannins reacting with iron. If the fittings are plated, solid brass, or stainless steel you should be fine.

[Mallethead]

Thanks for clearing this out. I use a lot of recycled buckles, hooks and rings, but now I at least know that I should at least use a magnet to test critical parts. Looks like at lot of times buckles are made of other materials and only the tongue is made of steel or other material containing iron.

I think I'll try some clear PU varnish or similar on buckles if I find a suitable product.