Part of the pleasure of firing pots using the raku process lies with the unpredictability. A raku potter can control a number of things- these include:
- chemistry of glaze
- thickness and application texture of glaze
- temperature, duration and intensity of the firing process
- level of oxygen in the firing atmosphere
- length, timing and intensity of post-fire reduction
So- having acknowledged the vagaries of raku- I still have say that this &**@# Egyptian blue glaze is in its own league in terms of willful lack of constraint.
At its best- it yields a mixture of vibrant reds and oranges, with copper bits... and then areas of sky blue where the glaze is abraded. The two views of the vase (below) are good examples, as is the shot of the 'bowling ball with breaking wave' piece (left).
(I had a kid look at one of my pots once and yell 'that pot looks like pooooooooooo!')
OK- that's a bit harsh... but it's definitely not the effect I'd like to see with this glaze. I do like the way that the example on the right 'flashed' on the rim of the carved mountain design (very sunset-like).
- I think that the 'weathered sandstone' texture stems from a lower firing temperature...
- I think that the complex color scheme stems from a fast, oxidized firing followed by a strong post-fire reduction
- I also theorized that the 'layered' appearance was linked to a thicker application of the glaze
The first piece out was a classic 'algae delux' model... but not too unattractive. It also has more of the glassy texture than I wanted. Still- not unattractive.
The second, which was pulled sooner and reduced more intensely, had the same surface texture, but more of the blue highlights that I'm looking for (but without the reds and oranges). See below.
Here's the recipe, if you're interested in telling me what I'm doing wrong.
Soda Ash 30.5
Lithium Carbonate 8.5
Black Copper Oxide (added) 2.5