the cracks and the crawls

another firing; luckily there was a day when there wasn’t a wind from anywhere near the East, which blows straight down the duct and puts out the gas flame. the ambient temperature was below freezing, so the exhaust from the kiln for the first hour after lighting steamed like breath: damp air from the glazes and the wax burning off.

smoke not small

it was quicker firing again – fourteen and a half hours compared to the eighteen I used to take.


a lovely green flame at 1207C – copper vapour from the black glaze. two days to cool down to 20C and opening time. it always takes a while to chip off the clay clamming and get the bricks out, clean them up and sweep up the mess.

in the kiln

everything looking good, glazes matured properly. one black piece had glazed itself to the kiln shelf, a run through the crack in the form where glaze had accumulated inside at the base, but it’s a soft glaze that knocks off with a chisel easily.


I had placed pieces strategically so that the matt ivory porcelains were next to the black-glazed pieces, with the result that two of them had acquired a beautiful raspberry blush. I love this effect.


the porcelains are firing well with no deforming at cone 10, and the “frozen snow” – chun over crawling slip – doesn’t seem to mind where it is in the kiln;

16 smallfrozen snow pod form 46 x 10 cm

this one was right next to the burner at the back, no problems. I slipped and glazed these by dipping right way up and upside down, which accounts for the change in colour and texture, and on the taller ones there was still a gap, so I had to paint the glaze on in the middle. I would need big dustbins full of the slip and the glaze to cover them without dipping both ways.

17 frozen snow pod form detail

you can see how active this crackle slip is. also the chun becomes dark blue over the red clay body (grogged pink stoneware), which is purely optical.

06 glaze detail

I am not quite sure what is causing this veined effect – again it’s the chun over the pink grogged – perhaps it’s the effect of slipping the bisc ware and the body holding some part of the slip’s constituents even where the slip isn’t covering it. and a very dramatic crawl from the crackle slip.

rose red detail

even more drama from this porcelain when it splits, and the colour is verging on lobster. porcelain is very different stuff from clay, quite different to work with. this is potclays grogged porcelain – still splitting even when grogged. the structure of the particles must not be able to cope with the curve I am putting on it compared to the thickness of the slab – so the inside shape compared to the outside shape is putting too much stress on it. the spiralling split combined with the fleshy smoothness of the porcelain, and then the pink reduced copper “sprayed” onto it in the terrific temperatures of the stoneware firing – well, I think it’s something quite special.

black glaze detail

this is a close-up of one of the black-glazed porcelains. you can see a crystalline thing happening, which is very nice. this glaze has an equal amount (23 %) of dolomite and of felspar, and 25% of china clay, which keeps it quite stony, it also has 6% of copper oxide and .75 % cobalt. a lot of copper, no wonder the white porcelains are blushing.

black white detail

on this one I only slipped the top half, and allowed the run to happen, knowing that I would get the lovely dark almost black chun without the slip.

you can see the rest of the pots here, in the hideous flash gallery. I do hope to find some better way of showing the pots than this eventually.



  1. Jane. This work is truly beautiful. I am in awe of your attention to the chemistry of the minerals you use. Wish I had more influence at Yorkshire Sculpture Park these days as your work would sit beautifully among some of their internal exhibitions. Just wondrous. Thank you for the detailed explanations. Biddy F.

  2. Hi Jane, I have just come across your blog, I was looking for a crawl slip/glaze, and was wondering if you would be willing to share….I work mostly in Raku and some stoneware ^6. any information would be appreciated.

    Wonderful forms,,, very nice!

    1. hi the crackle slip is very well known, it comes from Daniel Rhodes’ book on clay and glazes. google it and you will find it! in fact at this moment I would have to google it as I don’t have it on the computer. all my work is stoneware, so I can’t help you with raku glazes. the crawling shino is from ian currie.

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