Case hardening with Kasenit is one of the FEW things I seem to be able to do well without problems. Parts like the plate, cock, and bridle, are usually 8620, which is a mild steel and can be case hardened without tempering (though I still will temper slightly afterwards, just in case). Frizzens are almost universally made of 1095. This is plain, ordinary, simple, and YES, water hardening steel. When I do a frizzen, this is the procedure I use. Using an oxy-acetylene torch, (there is NO WAY you could ever do this with a propane torch), heat the part to bright orange (I NEVER see steel glow "cherry red"...). If there is a question as to heat, take a magnet and try to stick it to the hot part. The point at which it no longer sticks is "critical heat" and is where you need to be. Coat the part with Kasenit and keep heating. I usually watch my reflection in a large, shaded window rather than look directly at my work. I lost my goggles and wouldn't wear them even if I had them. When heating, I heat the whole part, but only really worry about the striking surface. Keep heating and adding kasenit. Again, the Kasenit should be put on HEAVY. You should hardly be able to tell the shape of the part you are working on. I usually keep going for about 10 minutes. When ready, I quench in warm, dirty water. The Kasenit will come off with a very satisfying "POP", and the part will come out of the water relatively clean and with nice colors on it. If it has lots of goo, very likely it was not hot enough when you quenched it and you need to do it again. Now, for lockplates and bridles, all I do then is polish off the inside of the plate where I can see my temper colors and temper it down to a "straw" color. This doesn't really temper the hardness down much, if any, but in my mind I think I'm relieving any stress that might be in the part...
On frizzens, all those pretty colors have to be polished off (I have always been able to get really nice case colors with Kasenit) so it can be tempered. I hold the frizzen upright portion with old pliers and heat the tail of the frizzen first with the color going to blue in the tail and maybe purple through the screw hole and into the pan cover area. When this is reached, I put the frizzen face down on the anvil to act as a heat sink and continue heating CAREFULLY on the front side of the frizzen upright. I can do one so that the front of the frizzen is a straw color while the rear striking surface is uncolored and still full hardness. I have always done them this way, and have always been very successful at making frizzens that spark like wildfire, and none have ever come back to me.
