I have worked with Osage for 40 plus years on selfbows. Yes.. it does turn too a wonderful dark brown. I have one of my first selfbows thats almost black. But if you peel back the leather grip wrap...you see its lighter. So I do think light does affect the wood (a so called tan) .I'd be afraid to say using it as a stain..if light would make a difference. As time would age it in so many ways. It would be hard to say the stain did it. Wish there was a way to find it out though???