# Can you heat Bismuth crystals to reset the oxide layer for new colors?

I'd like to get a bismuth crystal with small structures and deep blue colors for a ring I want to make. I can find these properties in different crystals online but never together. Can I just take a crystal with the right shape and blowtorch it to create a new oxide layer? Would I first have to chemically remove the thin oxide layer?

• I have made Bismuth crystals where I etched the oxide layer off and tried heat treatment to reproduce the colored oxide layer. It did not work in a $200^\circ C$ furnace, but that doesn't mean a torch couldn't, I would suspect that it is non-trival though. – A.K. Oct 16 '17 at 19:59
• Just a thought, but perhaps a thin oxide could be deposited by making bismuth the anode in a dilute sodium or potassium hydroxide bath. – A.K. Oct 17 '17 at 3:25
• Would that bath "redo" the oxide layer though? And wouldn't that create a thicker, more even layer than one resulting from the uneven cooling of a crystal? Also, do you know if nail polish would work to preserve the layer without dissolving it? – CoolGuy47 Oct 17 '17 at 4:27
• thickness is a function of time and current Nail polish remover will not dissolve the oxide. – A.K. Oct 17 '17 at 13:00