Wednesday, August 11, 2021

What's Taking So Long?!

Glazing and testing. That's what's taking so long!

I got my mugs fired, as you know, but then the problem of the right clear glaze came up. I called up Amaco, which manufactures my underglazes, and got the skinny on what they used for the clear they use on their high fire test tiles. It can't just be a regular clear because of the underglazes; the zinc in the glaze can react poorly with the colors and you end up with a milky or foggy layer. I found out they offer a dipping glaze and ordered it. And waited.

And waited.

And waited.

Finally I call them back. It turns out the raw materials are hard to get (thanks, Covid-19 and Delta) and they didn't know when they'd have the dry glaze mix available. I ordered from one of their distributors, but almost immediately got a call that they didn't have it. I found myself wondering why they didn't have it marked, "out-of-stock," but whatever, right? I finally found a gallon jug of the brush-able stuff and had it shipped. So now, of course, the quick dip has turned into painting several coats onto each piece, which is harder than it sounds. A second coat can start pulling up the first coat and the ceramist starts to strongly consider a nervous breakdown!

Meanwhile, I started the touch-up process on the things I'd already fired. When the clear finally arrived, I was good to go, but for one thing.

Underglazed ware, waiting for clear glaze.  

The glaze test.

Normally, I'd dive right in and take all my glazed stuff over to the nearby ceramics center for firing and damn the torpedoes, but I needed to test it first. The Supernatural-inspired mugs were a ton of work, and the thought of having all of them ruined makes me sick to my stomach. As much as I'd like to just forge ahead and hope the Kiln Gods are feeling happy today, I had to cave in to good sense and start a glaze test.  

 The original plan was to put one cup into their firing for testing, but since the ceramics center isn't doing an oxidation firing for another three weeks, I went ahead and decided to take a chance in my own kiln. I have too many people asking for these to keep them waiting! I started it this morning. You'll note the screen says it's eight hours and twenty minutes to complete the firing. It's likely to be the day after tomorrow before I can safely open the kiln at around 100°.

Non-ceramics folks won't know that having all of the pieces of your glaze firing working together is paramount to a successful firing. What that means is the clay body and the glaze body have to "fit" together; the technical term is "glaze fit." The glaze can't shrink in the cooling process faster than the clay it's being fired on, or you can get shivering or crazing in your glaze, which makes it unsafe. The clay body is my favorite 8-11 buff, which means it can be fired to vitrification (leak-proof) at cones 8 to 11. I decided to try this test at Cone 8, which is roughly 2320°. I figured since the glaze is primarily for cone 6, the closer I kept to that temperature, the better my results would be.

I'll let you know in a couple of days.

All hail the Kiln Gods! 


  1. Wow - so much can go wrong. This is a real labor of love. Good luck with your glazes.

  2. Ah! The fun part of pottery. I work in low fire but I have to be equally careful with my clear glazes. The main problem is clouding when they are too thick. Which is why I stopped dipping for the most part. One brushed coat is usually sufficient.
    Happy days and toes crossed for great results.


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