Any potter will tell you that testing glazes sucks.
There is just no easy way to do it. It's time consuming and tedious, truly an evil necessity if one is looking for their own glazes that stand out in a crowd.
So I spent many hours this past week doing what I hate: testing glazes.
It has taken me many years to get to a point in glaze testing where I'm no longer rushing through it as fast as I can. I've made WAAAYYY too many mistakes doing just that. I've finally learned to slow down, clear my schedule for the afternoon, pull up a stool and get it done right.
So this time around I'm working on two different glaze bases: a glossy from the geniuses at Digitalfire, and a matte, a recipe that was given to me from the amazing and talented people at NSCAD. I will spend hours researching the colors that I am looking for: what ceramic oxides will yield what results, what ingredients are necessary in the base glaze to give the desired effect. I hunt down appropriate base recipes and calculate them using Insight, a downloadable glaze calculation program (highly recommend it!) and make sure all the numbers look good.
With all the research out of the way, I mix up 500g batches of each, with no colorants, and run each batch through a 120 mesh sieve. Then each glaze is weighed and divided into 5 different containers, all carefully marked with my trusty sharpie. It is at this point that the real test mixing begins. Colorants and stains are carefully measured into each well-labelled container (learned that the hard way, more than once!) and are then ready to be applied to test tiles.
I used to use lots of itsy-bitsy L-shaped tiles that I extruded. Each glazed surface was no more than 1" x 2". I have since moved on to larger surfaces. I found I just couldn't get enough information off of that small a surface. I need to actually SEE what the glaze is going to do, in the manner in which I'm going to be using it. Now I extrude tubes, about 3-4" tall, and 2 1/2" wide. This gives me lots of room to try as much as I need to on the same surface. Each tube is CAREFULLY labelled (also learned that the hard way, more than once!) and at the same time, I make very thorough notes in my sketchbook (again, the hard way...).
Glaze testing is painfully slow. After the research, there's the mixing. After the mixing, there's the firing. After the firing, you have to wait for the kiln to cool. After the kiln cools, you FINALLY get to look at the tiles, and inevitably, try to figure out what to adjust the next time around to get the results you are looking for. It can literally take weeks, months and even years to finally hit the jackpot and get what you were looking for in the first place. As frustrating as it is in the thick of it all, when you finally get that perfect glaze, all of that time spent doesn't seem so bad. It's like hitting pay dirt.
So for all of you out there who are also enduring glaze hell, hang in there! Without all the testing, you'll never find what you're looking for, and sooner or later your efforts will pay off.