If you make your own glaze recipes, you use ceramic raw materials with hot air… or “LOI” for short. Sometimes this LOI is removed from the raw material beforehand by “calcining” it. But what exactly is that and why do ceramists do it?

By hot air, I don’t mean (this time) all the crap that bloated types spew into the ether. I’ll probably talk about that another time, but this time I want to talk about “Loss On Ignition” or the abbreviation LOI. In other words, the evaporation of substances by intensely heating them: calcining.

Let me explain using the raw material kaolin and a kiln that we will fire at 750 ⁰C (1382 F). Time for an experiment!