Friday, 4 March 2011
Slip tests - desperately needed.
Well, these are my slip tests. I have a whole load of pots that desperately need slipping, but by the time these are done, I think they're going to be past that stage, unfortunately.
So, there are three tests. I have worried a bit about what to try, and I settled on these. Three left are 50/50 china clay and hyplas, three middle are 100% AT ball clay, and the three on the right are 50g china clay, 200g hyplas plus 100g thick but wet throwing slop (ie red body clay.)
You're probably thinking, what the hell is he doing? Well, I don't know what I'm doing, really. The continued use of hyplas is because it's what I've got, and at the moment, I have no money to replace it. I have a little AT clay and thought I'd use it.
So the 50/50 is an attempt to bring down the silica and reduce (?) the thermal expansion of the slip. The AT is because the old potters used ball clay as their slip and it is just lovely to use - much nicer than the other two. The third is sort of half and half an attempt to temper the silica, and to follow Kemps advice of one part body clay to some parts of ball clay.
Alas, each is mixed to some unknown consistency, and, by the time I'd got to the second slip test, the pots had dried considerably in the sun. So the last six pots got a wipe with a sponge, where as the first three didn't. I'd rather everything had been the same, but I was a bit concerned that I was putting slip on when they were too dry.
Anyway, I hope to have these through by Monday. I have two bigger pots with black slip that i've bisqued over night, so they're going to get a draw-through glaze treatment in a minute (after a cuppa.) They are too big to fit in my little kiln together, so I experimented and took the lid off and built the wall up using K26 bricks and some fibre stuffing. Seems to have done the trick, although the firing was quite an anxious one (lots of steam from the bricks - and it was dark and late and quiet - fun :)
Right, that's all.
Posted by potterboy at 04:03