Here is a write-up on using Boric Acid paste to prevent scaling:
"One of the industrial uses of boric acid was listed as "hardening steel". I thought "That's odd... I don't remember that being a step in my heat to cherry red, won't attract a magnet, quench in the backfat of a virgin slave on the harvest moon heat treat procedure." So, I did some more looking, and found that our friends in the jewelry and gunsmithing community use boric acid to prevent scaling when heating precious metals or heat treating precision firearms parts. It prevents oxidation and washes away in hot water or in alcohol, and that is the one thing that boric acid is very soluble in at room temperature.
Anyway, once I was resonably sure that anti-scale compounds were by and large just boric acid, I had to actually find a source of the stuff. Boric acid is an excellent insecticide, and is sold as a safe, natural way to decimate the local cockroach and silverfish populations
Ingredients:99% orthoboric acid, 1% other ingredients. For a little more than $6/lb with no shipping, I effectively have the same stuff that costs 3 times as much. I bought a little denatured alcohol because I wanted to just dip and go.
Now, I don't think this is going to be the have all end all, as it probably starts to chemically attack steels at high temp. Judging from PBC's website, it's about 1600 degrees. That doesn't concern me too much as I use O-1 and 1095 a lot. At those temps, it might be best to use anhydrous borax and deal with the bark, or break down and use a commercial compound. I might have to try borax and try removing it with hot water with hot vinegar or cold muriatic acid. Borax is a base, so an acid might have better luck removing it than just hot water."
I've use this before and it does work.
