A few days ago I finished the hammer head I was making. I did most of the work in my machine shop class, and some of the work at my studio. I case hardened it last week in class. I really only case hardened it cause I wanted the mottled gray color, but I wasn't very happy with the way it looked. I tempered it and got some violet/blue colors on the lighter spots and I thought it looked good after that.
After the case hardening there were some areas on it that look sort of etched. It's not scale, I dont know why it happened, I don't know much about case hardening.