newtboy says... I agree. What I think it was was an acid bath, rinse, and maybe a coat of clear enamel or something to make it smoother? That's just a guess based on a minimal knowledge of metallurgy. Acid is often used to bring out patterns in cut meteorites and patterned steel. greatgooglymoogly said: I wish there had been an explanation as to why the pattern was invisible on the polished ring until immersed in the black liquid and coated by the brush.