January 16, 2012 § 2 Comments
One of the tasks for the winter has been to develop a set of glazes that I feel are mine. When I started making glazes for the first time in the summer of last year, I bought an Emmanuel Cooper book of glaze recipes and began from there. I found it to be a bit like scrabbling around in the dark and not being able to find the light switch. Every glaze I made crackled, so to compensate I thinned the glazes down until they flowed like water, which succeeded in getting rid of the crackle but the glazes were not as they should have been. I didn’t know how they should have been.
This is an image taken from an earlier blog post. It is a gorgeous colour but the crackle is no good if I am making tableware. What I was looking for was a shiny glaze but all the ones I was making were rough and scratchy.
Just before Christmas, I bought Linda Bloomfield’s new book on glazes, called ‘Colour in Glazes’. In there I found a recipe for a shiny base glaze (potash feldspar 27, whiting 21, china clay 20 and flint 32) fired to 1260 degrees centigrade and I’ve been trying it out.
It is much more what I’m looking for and I think I might have found at least one glaze that I love and want to use. My problem, though, is pinholes.
This is how the glaze is going on, although the thicker the glaze is applied the more air bubbles there are (the left hand side has been double-dipped).
And this is how it is coming out. Not great. In Bloomfield’s book, she says that you can eradicate pinholes by soaking for 15 – 35 minutes or exchanging the whiting (it emits carbon dioxide gas during the firing) for wollastonite and reducing the quartz. I am having some trouble with my kiln, which is not reaching the top temperature, and I’m not sure if it is soaking. Hopefully, this will be sorted out on Thursday and then I will have an accurate idea of the temperature the kiln is reaching and whether it is soaking or not. If the pinholes remain, I will try wollastonite.
In the meantime, I am thoroughly enjoying playing around with the various oxides.
The left hand glaze is an addition of 1% cobalt carbonate and 3% copper oxide to which I added 1% nickel oxide to get the right hand glaze. I love the depth of the grey in the right hand glaze and it will be the first glaze that I have made that will become part of my set of glazes. You will also notice that there are no pinholes – the thinness of the glaze, I presume, it has had a chance to melt thoroughly. This gives me some hope that with a good soaking the problem with the thicker glaze application might be cured. We shall see…
The right hand glaze in the picture above is also potentially in my set of glazes (the above base glaze with the addition of 1% cobalt carbonate, 1% red iron oxide and 2% manganese dioxide). Now I need a black and a white – possibilities currently in the kiln…