I fire this up over 1000C - just enough to bisque it, remove all plasticity and calcine any stray pieces of limestone that are (unfortunately) in it. As long as this happens the pieces teun into calcium oxide and do their expansion and crumbling up when they are added to the wet clay (rather than when glaze fired!)
A lot of the clay I use is highly compacted and very hard. This is one of the few clays I have found that I can use almost as it is, with no additions - though it needs a lot of work with the hammer before adding water to slake it down. I have managed to dry out these clays, which makes them easier to slake - no mean feat in British weather!
The final Clay For Today is this unpromising gravelly looking stuff. It is a crushed and slaked carbonaceous ball clay that actually fires quite white when all the carbon burns out. At the moment it feels completely non-plastic but with a lot of kneading it becomes quite a reasonably useable clay.
I am chuffed your writing about the clays youv'e found and are processing been following the blog for a while and saw the interview when the firing was going on and I was really interested in the clay side so cheers for the post. I love the fact that kneading it a lot improves it so much and it must be well worth it. Alas I have only dug and processed and then threw the clay myself once but it was the most beautiful clay to throw and the whole process was really enjoyable it was an ochreish earthenware very bright orange made a really nice slip under high fire glazes. Anyway keep up the hard work and I think the pots are magic.
ReplyDeleteThanks for your comment! It really is a treat when you find a clay that is beautiful to throw. I have a few but sadly none are refractory enough for stoneware temps.
Deletesuch hard work! I think you need a bigger hammer though.. good on you for using found materials.
ReplyDelete