Glaze Testing Class and What Happened?

Opening the glaze kiln is by far the most exciting part in the ceramic process, it’s the big reveal of what you’ve been working on. During this class session on glazes I’ve been firing every week, and it’s made for a lot of anticipation and ‘So, what happened?’ We’ll be wrapping up in a couple weeks and although it’s been challenging at times, I think everyone’s been getting some interesting results and gaining more control over their work.

I’ve been testing a lot of new things too and discovering some really interesting surfaces. One of the areas I’m working on is finding different, beautiful finishes for my African Vessel series. They aren’t functional so I have a lot more freedom with how I finish them.

I’ve been experimenting with different raw materials–mostly sands and soils in my area. For example, I had collected some sand from our local creek awhile ago, and mashed it onto the surface of an unfired pot. When I took it up to cone 8 temperature, the sand melted beautifully and made a slightly sparkly and slightly rough finish.

I’ve also tried that same sand mixed with a low-fire red clay and brushed onto a test tile. I thought the low-fire clay might melt a bit at the high-fire temperature but that didn’t seem to happen. And while glazes tend to look distinct depending on the clay body they are melted onto, these sand and soil/clay mixtures don’t seem to.

I knew that ash of different kinds had been used as part of glazing for centuries. Work fired in a wood burning kiln can be glazed entirely with only the coating of ash that gets deposited by the flame moving through the kiln. I’ve only used it once before as an accent on a brown clay piece and it turned out shiny and dark.

But these two little tiles showed me something new. I had simply mixed some wood ash with water and painted it on the tiles. When I pulled them out of the kiln and saw the results, I realized that the ash itself doesn’t have any color and the difference between them was only due to the clay bodies! I was very surprised and ready to try a bunch of new mixtures.

This has been a really interesting session and the most like a school science class that we’ll ever get to in my classes. Everyone is getting an opportunity to learn from other people’s trials, so there’s a lot of information being generated. It will take some time to absorb, but the great thing is these tests exist as a reference to go back to when you have questions like-What happened?