Don't know if everyone knows about Glazemixer.com but they mix up recipes and ship them to you dry.You add water and you are off. That way people who don't want to buy and store all the chemicals can mix up glazes a lot cheaper than buying them wet from Duncan or other glaze suppliers.
And the best news is that they now print the recipes - so it is open source!
Couldn't be a better way to do things!!
I found this out by Googling "Cowan Amber glaze recipe"