In the 1950's an Arizona USA Gunsmith named Roy Dunlap published a book "Gunsmithing". In this book he mentioned using Ammonium Nitrate fertilizer as a component in a home brew Hot Salts bluing formula. I tried some of it & it did produce a good blue but had an excessive amount of Sludge in the tank, am thinking the inert filler mat'l had been changed from when he had used it.
I believe the term "Temper" is correctly used alone. To temper the heat treated steel you Draw the Hardness, you do not draw the temper.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra