[HisSoldier]

I learned more on this;

"Color casehardening requires more care. In color casehardening the parts need to be immersed in the carbon material in a sealed container and the temperature is critical for if it is too high the colors will be poor and washed out. Few people know it, but it is actually possible to get very good colors under the critical range; however, if this is done you are not really casehardening, just coloring. I have found that temperatures should be close to the 1400 degree F mark. When the temperature climbs much over 1450 the colors seem to be rather poor. Just as important is the process used to quench the parts. If air contaminates the parts before they hit the quench the colors will be spoiled. For this reason it is very important to make sure that a method is devised to allow the parts to be moved directly from the crucible to the quench as quickly as possible. For this reason I have devised the following crucible seen in the photograph below."

I watched a video of an Italian replica gun maker "Color case hardening", but the quench colors looked more like about 1100 degrees, maybe 1200. At that temperature there can't be any hardening, though it's been an argument between myself and an employee years ago.

The paragraph I show above was taken from an article on color case hardening I found in a model engine forum, the author of the extensive post shows some samples of what he does and it's interesting enough that I'd like to buy a good electric furnace. I'd post the URL but it might be against the rules.