Really serious potters should take advantage of John Britt's Free Online Glaze Course...on YouTube.
In case you (as a potter or just curious person who may like pottery) didn't know, John travels all over to give intensive workshops to groups of potters, who make test tiles as well as glazes, fire them and learn all about the glazes they could possibly want to know - at a nice cost of course. So this free version should be of interest!
