back to glaze firing with a stack of biscuit pots to experiment on. this time I tried to recreate something which happened five years ago. of course it didn’t work exactly, but I got some interesting pots. I used my old magnesium crawling glaze, which has a wonderful matt marble surface, sometimes it heals up again after crawling, resulting in a network of slightly shiny veining. it needs a lower temperature, between cones nine and ten, and different parts of the kiln do different things to it. it also needs a very smoky intense reduction all the way from 1050 to about 1230 Centigrade. with heavy reduction cone nine will go over at about that temperature.
I first dipped this pot head first into the barium glaze, which I had thinned down rather a lot. putting another glaze over it if it is thick is a risky business as it can just all peel off almost straight away. then the overlapping layer is the magnesium glaze. it was very near the gas burner, so parts have really over-melted; it is not what I expected, but I still think it works.
this jar has one coat of the magnesium glaze. the clay is white stoneware with an impure fire-brick grog, and the impurities give these black markings. it is slightly under-fired, it was on the floor of the kiln, but it has come out a good reduced dry matt grey-white, and the crawl is a little rough textured.
this big bottle (47 cm) has the layering like the first and I am very pleased; I think it is the best pot of the firing. it was next to the flue, which is a hot spot in my kiln. the other side of it has less melt, more crawl. also the barium glaze has produced a good colour and texture with the heavy reduction. it leaves the clay a rusty buff, where the crawl has pulled the glaze away, even though this is a white stoneware.
this pot has a layer of porcelain over a medium buff stoneware, so the magnesium glaze is a little different. the crawl lines are interesting.
the rest have variously reacted to the lower firing – in fact it was slightly lower than I intended, cone 9 didn’t bend right over; I couldn’t draw out the spyhole brick, it had got chipped and the chip made it stick, I had to look through the little plughole in it. the barium glaze doesn’t seem to mind at all, it works fine on the top shelf or on the floor of the kiln.
this is my blue dolomite glaze over china clay slip, and it could have done with a less smoky firing, the blue would have been clearer.
again, the barium glaze, absolutely fine, doing what I intended – lovely crusty surfaces over the sticky porcelain slip and powdered china clay.
this is the blue glaze again and it IS really under-fired – I will re-fire.
another experiment, manganese oxide painted on to the raw clay and scratched off again in parts, then the blue glaze over it. it was a good thing this was fired at a lower temperature, the oxide did make the glaze run slightly on part of this. I like the metallic blue. I will have to try less oxide and more scratching off.
I got several of these crusty little bottles
and the black clay that I cut with buff stoneware – about the same and more stable, so that was a useful process, and it saved on expensive clay too. there are quite a few more of these to fire, I will have to try some other glazes on them.
so – various paths up which I hope to explore further. the whole firing can be seen here