Saturday, January 24, 2009

Soda Craze-y?

We finished up the test soda firing last night and cracked it open the next day. The nice thing about the kiln size is that it cools fast!

I'm feeling crazy for crazing! I did a series of tests on the honey colored glaze below to try to get it from crazing so badly. I tried some varied tests by increasing the levels of silica, lithium, and spodumene. Only, the problem is, even though I did something different to each tile, they look all the same! They are all crazing now because of the soda hitting them. So does this mean I can't win?

I'll have to try further testing because this could work fine inside a bowl where it doesn't get hit with as much soda. I definitely like the color so when I did this test I kept that variable the same.

On with the craziness!


June Perry said...

Joy, what's the recipe? It may not have enough ingredient like whiting, magnesia, barium, and/or high alumina, etc, which help repel the effects of soda.

Lithium 3% or so can lower expansion as can added silica, but if you don't have enough soda repelling materials in the formula and you're hitting it directly with the soda, it's going to keep crazing.

Till later,

Joy Tanner said...

Thanks, June that's a good thought. Although I increased the lithium and silica, I didn't change the F-4 in the glaze, which was also contributing to extra soda. I didn't try adding more clay/alumina b/c I didn't want it get too matt since I want a hard glossy liner. But maybe adding a little bit more could help. Here's my recipe:

SS Base (honey version)
F-4 21.9
Stront. Carb 12.5
Grolleg 15.6
Silica 24.7
Lith. Carbonate .3
Frit 3195 6.3
Wollastonite 18.7
with iron 1
titanium 4