I'm always testing glazes (and lately clay formulations). I cannot remember a firing that did not have at least some tests tucked in between mugs in the kiln. I fired ten days ago and this morning finally had a chance to look over the latest series of glaze tests. This test, which was provided in Matt Katz's online glaze class was showing what a single coloring oxide looked like, and what it looked like blended with one other colorant. It's a test to give a rough first pass, an idea of where you can go with further tests. And, there are several test tiles that yielded some fabulous colors that won't need further refinements. As a potter, I cannot imagine not doing this type of testing. Yes, it is work. But damn, is it ever fun!