I want a cone 6 strontium blue crackle glaze. Strontium reacts with copper to create a unique shade of blue that isn't easy to create with other fluxes. Originally potters used barium but many people have switched to strontium because it is somewhat less toxic.
I'm not particularly interested in strontium mattes. Right now I want a glossy glaze. There are still concerns about strontium and copper leaching from the glaze, so I won't use this on food surfaces. That also gives me the opportunity to make a crackle glaze.
| Oxidation | Reduction |
|---|---|
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I ended up not seeing any crazing. However, this is still a rather fluid glaze. It melts into a very thin layer and has a very attractive light blue color. There was significant pooling at the bottom, which means I can apply it thinner.
The glaze is a gross red in reduction. This glaze would need significant changes to become a proper copper red glaze. However, I'm not interested in going down that rabbit hole anytime soon :)
I think the boron content can be reduced slightly. The decrease in frit also decreases the calcium content and increases the amount of strontium. This should also give a slightly deeper blue. I also decrease the flux and increase the silica for lower thermal expansion.
| Material | 3269 Sr | 3269 Ca |
|---|---|---|
| Mahavir Feldspar | 25 | 25 |
| Strontium Carbonate | 25 | |
| Whiting | 25 | |
| Ferro Frit 3269 | 20 | 20 |
| Silica | 20 | 20 |
| EP Kaolin | 10 | 10 |
| Copper Carbonate | +2 | +2 |
I also made two alternate recipes to see the effects of the secondary flux on the copper color response. These use a rarer frit, Ferro Frit 3269 to give me complete control over the secondary flux content. I can blend between strontium carbonate and calcium carbonate to see what ratio produces what colors.
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