Raku Base Glaze No. 1A
Ferro Frit No. 4112 60%
Ferro Frit No. 4108 30%
Silica 200 10%
As you see the glaze has no clay to suspend it in water and to provide adherence, please use bentonite 5% or a gum which you can buy in liquid form from a Pottery Supply shop.
To this base add oxides of copper (1-4%), cobalt (1/2-1%), iron (3-8%) to achieve many colours -Green, blue, tan under oxidation and red, purple, rainbow under reduction. To increase your chance of winning, use the base glaze in triaxial diagram configuration with opacifiers e.g. tin oxide 5%, titanium dioxide 10% and the third apex with no opacifier. The base glaze when used with one oxide addition on triaxial bases will surprise you with many very attractive glazes.
Raku Base Glaze No. 1B.
Ferro Frit No. 4112 57
Ferro Frit No. 4108 9%
Barium Carbonate 15%
Silica 200 19%
This base glaze is an opaque glaze without an opacifier, and please use it in a similar way as the first glaze. (Do not forget the bentonite).
Both glazes have a firing range 850oC - lO5OoC depending on the oxide addition.(We all know that metallic oxides of copper, iron, cobalt and manganese are very potent fluxes in fritted glazes containing boric oxide). I suggest firstly fire all the samples under oxidising conditions in an electric kiln and then pick up the good looking ones and fire them under reducing conditions in a gas fired test kiln (reduce strongly on the way down at 800-700oC) to simulate Raku firing, and again pick up the best samples for the real test when you do Raku firing.
Cheerio for now
Mike