I've had a number of good chats recently about this one with Mistress Ælfwyn. Master Dafydd from Petrea Thule was also giving me some tips at Feast of the Hare the other week. To paraphrase Mistress Ælfwyn, I'd be a goof not to do the black dye since its the easiest one to do. :)
The first step for my period black dyes is always using rusted iron, so I needed to find some rusting metal. I had thrown a bunch of cheep nails in a jar with vinegar to prep them. Turns out they won't rust that way (no oxygen) so I need to restart the experiment.
Basically the iron oxide in the rusted metal is supposed to react chemically with the tannins in the leather and turn it black. The recipe I plan to use actually boosts this reaction by pre-treating the leather with oak gall to add even more tannins. I'm hoping this will make a darker, truer black.
The vinegar didn't get me any rust, but just for fun I wanted to see what would happen if I applied it to the leather. I figured maybe I'd get a little bit of a colour change, even just a bit darker would be neat.
Well, so much for that. The pics below show just what happened, it's a true black. I really have no idea why this worked. The vinegar had started to dissolve the metal, so there was definitely some metallic material in the solution. No idea what it would be though. Would iron oxide form without rust?
This piece has a coat of olive oil added and it just made the black pop, looks almost like modern black leather.
If I'm going to use it for my project I need to do the period documented recipe, but this is still really cool. I may still bring it next weekend just for fun.