Expert: Sam Kelly - 11/28/2008

Question
Hi:
I am looking for a 'recipe' for cobalt blue that I can use to decorate my ware and am uncertain if a cobalt blue glaze results in the blue colour over white base glaze.  I have done so in the past but did not formualte my own glazes at that time so am uncertain if there is a difference.  I am a novice recreational potter and live in a small community so am learning by reading, info from my guild members, internet and any advice I can obtain.

Many thanks.

Answer
Hi Debby,

If you have the base glaze as a powder add 1gram of cobalt carbonate to 100grams of base glaze powder, mix in 100mills of water.

If the base glaze is liquid weigh out 150grams and add 1gram of cobalt carbonate powder.

Test for intensity of color, cobalt is a very strong so you don't need much. The white content of the glaze could be additions of tin or zircon or both. Tin can do some crazy things in a glaze.

You can also add a color stain to the glaze instead of the cobalt, between 3 and 5 percent to test.

Sam