Heatbath/Park Metallurgical supplies salts for hardening all types of high speed steels (HSS) including molybdenum, molybdenum/tungsten and cobalt. Large numbers of tools may be safely hardened in a comparitively short time with a high speed steel salt bath set up. These salts are designed for the proper heat treatment of HSS by balancing the composition in such a way as to insure as neutral a bath as practical, minimize dragout or carry over and promote easy cleaning. HSS tools can be treated rapidly and uniformily without oxidation, decarburization or pitting. Accurate and uniform temperature control is possible and distortion is reduced to a minimum.