In my last post I showed a couple of photos of glaze tests I had tried with new glaze bases. I thought that you might find the next stage of testing quite interesting (I do!!).
The base recipes (which give the white glazes) come from a "how to" section on Jesse Wiseman Hull's website, which should be a "must read" for anyone embarking in crystal glazing (I forgot to mention this one to Carlie Star in my reply to her comment on my last post).
Anyway here is the first one:
frit 4110, which is the way 3110 is numbered in this part of the world. I did not use CMC , but added 1 percent bentonite to assist glaze suspension and application. I am firing to the point where cone 9 is just starting to bend. The clay I use for my pots does have quite a fluxing effect on the glazes that are over it, so other clays may demand a higher top temperature. I have done a 3 hour soak at 1100 centigrade to grow the crystals as the kiln was cooling down.
Base plus 0.5 cobalt carbonate & 1.0 copper carbonate.
Notice that the crystals are large (up to 50mm) and have very distinct borders. As was expected from crystal glazes I have made with other bases, the copper coloured the background, and the cobalt tends to gather in the crystal.
Base plus 4.0 Red Iron Oxide.
The crystals are much smaller, and have blurry margins. There are nice light flecks in the background and crystal areas of this glaze.
Base plus 3.0 Red Iron Oxide & 1.0 cobalt carbonate.
The addition of cobalt has made the background and crystal colours richer. The crystals are larger, are almost matte, and are a grape-like purple.
Base plus 1.0 Red Iron Oxide & 1.0 cobalt carbonate & 1.0 copper carbonate.
Equal amounts of iron, cobalt, and copper do show three colours. The crystals have packed together with rather too much enthusiasm for much of the iron coloured background to show through, a slight adjustment of glaze thickness, top temperature, or a decrease in the amount of titanium in the glaze may sort this. I will also play with increasing either the copper or the cobalt to give more contrast between the blue and green colours.
Base plus 5.0 manganese dioxide
I had some difficulty applying this glaze. My first sin was to make it too runny, the second problem was that the addition of manganese tended to make the glaze want to form a hard lump in the bottom of the glaze bucket. The glaze is not all that nice colour wise at the moment, but is very interesting and complex when closely examined. The crystals have dark centers, and the most obvious crystal structures are surrounded by pale areas that extend a long way. I will play further with this one!
I am not having much luck with nickel on its own. I have tried it before with other bases with much the same result! This grew a very small crystal or two. I'll try again with just 1.0 percent nickel and see what happens.
No snow last night, and some sunshine here!!! Much better day than forecast by the met people.
Must dash now. Kiln to unload with some bisqued work.