The last conversation I had with Dr. Gaddy we discussed the possibility of coloring in the 600 - 800 F range and thought it could be done. Note that the color has to do with the thickness of the coating. Note that temper colors start to appear in the 400 F range and are done by 650 F. Temper colors seem to be films of relatively pure iron oxide whereas CH colors seem to involve more complex compounds via the "impurities" in the quench.
I don't know if anyone has tried forming CH colors at reduced temperatures, but I'd surely like to know if anyone has, suceed or fail.
DDA
