Substituting Whiting and Silica for Wollastonite
Occasionally I will have a potter who calls in desperation because they are mixing a glaze and run out of wollastonite and need it for a recipe they are mixing immediately for an upcoming show. Many don't do well with math or chemistry.
I bought a book in 1997 by Edouard Bastarache called Substitutions for Raw Ceramic Materials where he does just this for a variety of materials. He shows problems and answers. It is handy for pottery who don't have glaze chemistry software or much internet presence.
According to him: For a recipe where it calls for Wollastonite and you only have whiting and silica you substitute 0.863 and 0.0.513 respectively = 1 percent (gram) of Wollastonite.
Not perfect but pretty close in a pinch.
So if you recipe calls for 19.00% (grams) wollastonite, you take
19 x 0.863 of whiting = 16.4% (grams)
19 x 0.513 of Silica = 9.84% (grams)
Now you can just use that for your recipe but if you want to retotal it to 100 you will need to do some math. That is because whiting has about half its weight in carbon dioxide which is lost in the firing (LOI). So you will have 26.24 (grams) of whiting and silica vs only 19.0 (grams) of wollastonite.
Just so you know you can run this through Glazy.org which is a free internet glaze database to test it . If you get a better answer, let me know.
I bought a book in 1997 by Edouard Bastarache called Substitutions for Raw Ceramic Materials where he does just this for a variety of materials. He shows problems and answers. It is handy for pottery who don't have glaze chemistry software or much internet presence.
According to him: For a recipe where it calls for Wollastonite and you only have whiting and silica you substitute 0.863 and 0.0.513 respectively = 1 percent (gram) of Wollastonite.
Not perfect but pretty close in a pinch.
So if you recipe calls for 19.00% (grams) wollastonite, you take
19 x 0.863 of whiting = 16.4% (grams)
19 x 0.513 of Silica = 9.84% (grams)
Now you can just use that for your recipe but if you want to retotal it to 100 you will need to do some math. That is because whiting has about half its weight in carbon dioxide which is lost in the firing (LOI). So you will have 26.24 (grams) of whiting and silica vs only 19.0 (grams) of wollastonite.
Just so you know you can run this through Glazy.org which is a free internet glaze database to test it . If you get a better answer, let me know.
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