Originally Posted by The Forge
When I was at Hofstra University, there was a ceramicist teaching there who liked to try new formulations of clays for firing. We would compound and pug mill our own clays. The 'high fire reductions' were used primarily to bring out different colors in the glazes. I chose to put a pre-fired piece in the kiln and see what would happen. It was a mixture with a lot of iron in it. It started a light pink color and came out a deep, dark brown and shrunk. I was surprised how much it had reduced at least 25% in size. That's all I can tell you about it.
[That's interesting. Yes, I can see how a mix with a lot of iron oxide in it (which takes up more space than metallic iron) could shrink more than a normal clay body in a reduction atmosphere. I've certainly seen the opposite happen, where iron expands as it rusts, and sheds any concrete that's covering it. Maybe there's a new formula in there, for a special "shrinko" body. And 25% sounds more likely than 40%. ]