Some guys use lime instead of vermiculite. Always exercise care and precaution. Think about it.
In practice, you heat the blade and keep touching a magnet to the blade. This forces air up through the charcoal and is pretty close to genuine blacksmith forge.
You will still see the color appear from the tempering process, but there isn't enough carbon present for the metal to harden properly.
On your address label to us, do not put "custom knives". We suggest a double wrap for this grade.
Does Cryo really make a difference. Anyway once you have soaked it in the kiln at temp for many hours, leave it overnight, crack it open and you will have a case hardened Piece of steel. Simply put a lid on your quench oil container to smother it and put out the fire. If you can afford it, buy some and use it. I Made It! Allow them to remain draw for 2 hours. That means no scale and very little oxide.
If you see a warp, now is the time to bend it slightly back to being straight and it should take. Place blades in freezer overnight or for 2 hours in dry ice.
It's apples and oranges. Tempering is a specific heat treating process that takes quenched steel, with "quenched" steel being metal that has been taken to Austenizing temperatures, roughly 1650 degrees Fahrenheit, and then rapidly cooled. A metallurgical lab charges a fair amount to test for alloy and there is no home test kit that I know of "Look, Honey, it turned blue!