I generally use acid for this finish, esp for engraved guns where the relief is frosted and the high points are polished. The process brought up by Rocketman is interesting, I have quite a few turn of the century books on heat treatment and case hardening of steels. Many of them mention that if you want bright case hardened parts, ass sulfuric acid to the quench bath.

Mike Hunter
www.mikehunterrestorations.com