a better firing but some disasters

I fired the kiln again this week, and after much thought over the last result, I parked cones amongst the pots, and was careful not to over-reduce the firing. 

rather than the exit flame being the width of the remainder of the flue hole I kept it thin like this, with the pressure up (the temperature just didn’t rise without that pressure), and I started closing the flue off in the 900’s C, but no smoke and stink until I thought I had better make sure of a bit of reduction at 1060C, so I did for a while then backed off. no soak, Daniel Rhodes said not necessary, and I think I over-fired it a bit last time, so shutting it down before cone 11 started to move was better.

quite a bit of soot in the clay sealing the bricks, evidence of heavy enough reduction.

disaster number one – the clay holding one of the test cones on the shelves exploded – there must have been some air in it – and bits went all over the kiln.

this little bowl was ruined – a big chunk stuck into the glaze in the middle of it – and another had big enough crumbs in it that it’s a “second”.

even the top shelf had bits of clay all over it. the glazes must mostly have absorbed the tiny bits without them showing.

second disaster was this little bowl, which had been glazed before the last firing, but there was no room for it. the slip and glaze had raised themselves up off the pot in places .. this reactive crackle slip has nasty tricks up its sleeve if left. it vomited glaze all over the place

but the final effect is quite interesting and dramatic. all the glaze knocked off the batt wash on the shelf with no trouble.

I am looking for some different glazes. this is a recipe from Out of the Earth into the Fire, supposed to be a persimmon glaze, orangey red, like the Hamada Kaki glaze. however the original is made of crushed rock local to Mashiko, and there are various versions using normal western glaze materials. this has bone ash in it. I think my firing is too hot and too reduced to get the reds. also I don’t need to put it on so thick.

this little incense burner was at the top, but in the back corner, where there’s a bit less reduction. it has a lovely “tea dust” slightly metallic finish. I will have to try this again next time.

this is the star of the firing. it was on the top shelf at the front next to the flame, and it has just worked, a combination of the very deep clematis stem impressions, the dark clay, and the thickness of slip and glaze, plus the firing and location in the kiln.

this is my other favourite, with a very rich chun

the listening pod fired very well, and there were several good bottles and incense burners, more black clay ones as well as the chun.

I tried copper carbonate under the slip and got a rich greeny turquoise – not really my cup of tea.

these cones are 10 and 11 and I put several next to the flue wall in different places. this shows me that on the top shelf next to the flue is not a good place to put a pot unless I want cone 11 – a little hot for my chun. this is most likely why I got browny yellowy things happening to a couple of pots last time. the rest showed me that I’m getting good cone 10 temps except on the floor of the kiln.

I am happier with the big bowls this time, I put more slip on them, and more glaze. this grey stoneware one was on the top shelf and the inside glaze surface is actually amazingly un split and smooth. the other two are made in the grogged pink, which perhaps makes the slip react more.

I still like these a lot – I call this result frozen lace, they just have no practical use as bowls.

so a good result; I feel more confident of my ability to fire the kiln, and on the whole I think the persimmon is interesting and worth persisting with. the square plates were disappointing – the green/red glaze I used needs a darker clay body, putting on thicker, and not being squeezed into too small a space to allow the atmosphere in the kiln to work on it. however stacking on shells of Holkham beach worked – something to use another time. so, a few pieces to throw on the “shard mound”, and two or three which I might take to the shortlisting for the CPA professional membership next month.