more attempts with slip

the latest firing; a qualified success. I think I reduced more than usual … I was worried that the kiln wasn’t reducing enough, with the opposite result. it took an hour or so longer, which is an indication in itself …. but there were quite a lot of pieces so slow was good in that it gave the heat a chance to settle right into the corners. the cone you can see still standing is 11, which is how I normally fire – until 11 just starts to bend. I had more success with the black clay this time, with the tall piece on the left; I glazed it inside and out with my barium matt. the inside is a good sooty black.  the green/orange black dolomite glaze has a little trick of being definitely matt almost metallic black over the super-white stoneware layering, if I place it low down at the front of the kiln, so I can more or less rely on that. I tried the large bottle behind it with a combination of my barium matt and the crawling shino. very disappointing, quite nasty in fact. I have a photo of a bowl I glazed with a combination of shino and the barium matt two years ago, but on a darker clay, and possibly the other older shino, so that’s what made me try it this time, as it was lovely!

these two pieces are good examples of what you can and can’t do with the crackle slip. I had read that it stops crackling after the first day and you need to use it fresh. this is not true. the one on the left I slipped when it was bisque fired, and left it for a couple of weeks before glazing. you could see the crazing straight away, but I was worried that the slip would fall off when I glazed. it didn’t, and it’s fine. the one on the right, the blue, has handed off some of its copper content onto the one on the left, leaving it pinkish. I was trying for this effect. but the blue one was a last minute effort – I slipped it, then glazed it before the slip was dry. result – the glaze and slip have melded and pop off the surface with a small amount of pressure.

this little beaker was slipped when green (unfired). this does make the slip a bit liable to fall off , mostly on edges, but it depends on the clay body how much crackle you get. it’s quite restrained on this, which is St Thomas white, with the new barium matt glaze I found in Emanuel Cooper’s book (9% barium). this glaze leaves a rusty tideline on the paler clays.

the back half of the kiln was pretty crowded with lots of little pots. at the top some boring – I won’t put the Cooper matt on pale clay again, but the copper dolomite worked well over it – and the same matt rather boring over the porcelain slip – which is just porcelain bits melted down and brushed on – the chun over the porcelain slip is nice though – this little beaker is rather soft and delicate. sadly it leaks, or it would be possible to use it as a coffee cup!

probably in truth the chun is too delicate for domestic use though, I think it might scratch easily.

this beaker was also on the top shelf, it is the terracotta crank body which fires very dark, the crackle slip put on before bisque firing, and the chun over the top. the slip has rather parted company with the body, but the chun has fixed it, and melted into a thicker line along its bottom edge, with the pale blue bubbling which makes it so pretty. quite a drama for such a small pot.

here the slip was put on after bisque firing, over a toasty body which had been incised and painted with I think black iron oxide. the glaze is the chun again.

this dish was slipped on the inside when green … almost a disaster, it cracked the vessel … but hasn’t the blue dolomite worked nicely over the two different coloured surfaces and the spaghetti spoon indentations! the clay body is a mix of grey stonewares, reconstituted – a bit darker than the St Thomas white, with a lot of grog in it.

this is a bit special, it is one of the pieces I painted with slip made from Dameon Lynn’s fen riverine clay, with the chun glaze as a liner, and Cooper’s barium matt on the outside. the iron and the salts in the slip have reacted with the glaze, there are some bubbly tidemarks, and it is almost shiny. I should really redo the glaze with a more matt combination to counter this shininess, but the good thing is that the barium allows the warmer colour, whereas the chun is quite grey.

this time the black dolomite glaze on the porcelain is even better – somehow the heat work has been stronger and the glaze has almost begun to flow off the pot, leaving this gingery mustardy colour in a crystallised freckle. I am so glad I have this combination to take up what otherwise tends to be a dead space in the kiln, where nothing exciting happens.

and another bit of drama – crackle slip and Cooper’s barium matt glaze on the black clay. this clay looks good with the chun, fired on the top shelf – it has almost made a tenmoku.

until the weather gets better I can’t photograph these pieces properly, but you can see the rough cut here

altogether there were eleven rejects, including that big bottle – about a quarter of the firing.


  1. I really like the second to last one, with the giant nob on the side and the white stripe on the bottom. All very lovely. Too bad the cup leaks!!

  2. I loved the black piece in the first photo (also loved the copper-content handoff on the piece next to the blue one; serendipity favors the trained mind? 🙂 ) . What kind of clay is the black one? The only black clay I’ve found around here (Northern California) is low-fire only and that was very disappointing because I’d love to work with a clay that is intensely dark after high-firing. Are there really black clays that can stand up to high-fire? Sorry if this is a dumb question, but, as pretty much a beginner, I haven’t had much experience with the different clays.

  3. the black clay is from an Irish supplier, Scarva Earthstone, meant to be a sculptural clay, fires from 1160C to 1260C. the first piece is my copper dolomite glaze which can fire black if it feels like it!

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