Ok, as promised, I've been playing a bit.
Here's the piece of bone that I used for this little experiment:
Attachment 306276
I applied common super glue to the area on the right of the RED LINE/I let it dry overnight:
This morning I applied a pretty heavy layer of the Black Leather Dye:
Attachment 306277
After letting it dry for about 5-6 hours, I wiped the piece off. Very little came off:
Attachment 306278
So I soaked the piece in some Neatsfoot oil for about 3 hours and a bit did come off:
Attachment 306279
https://www.youtube.com/watch?v=gBzJGckMYO4