Step 4: HEAT TREAT
I’m not sure of the temperature needed, but dad taught me a little trick; when the knife gets nice and hot, stick a magnet to it, if it doesn’t stick your good to go. This happens because all the molecules in the knife have gone to a semi liquid state that allows them to drift out of alignment, something needed for magnetization. So after about 15 minutes in the kiln and checking it twice with the magnet we were ready to quench it.
To quench the knife you submerge it tip first into room temperature oil, vegetable oil in our case. This hardens the outside into a super hard shell while the inside stays a little more flexible. You have to do it quick so we held it over the oil and pretty much snipped the tip of the foil and it slid right in. you can jimmy it around in the oil a little bit till it cools down. Once that happens it’s into the over for an hour at 400 degrees. This step takes some of the brittle nature out of the steel, keeps it from snapping in half when you hit something hard.