> " Chili supplier and blend: I found a supplier who stone-grinds their dried chilis the traditional way rather than using a machine, which retains the luster, natural oils and bright red color that I needed the sauce to have."

This sounds remarkably similar to the problem faced by people who are into seriously expensive coffee. Basically, a "conical burr" grinder crushes the beans together, whereas a cheap spinning blade type grinder chops them apart into flaky bits. The former is strongly preferred by coffee snobs, and the use of the latter is seen as barely better than buying preground coffee.

My theory is that the stone part is actually not essential, but it's the crushing/grinding mechanism that preserves the oil and luster (could be done equally well with stainless steel), whereas some sort of shredding blade allows too much of the oils to escape.