A question for those who have the experience and knowledge….
A couple days ago I mixed up a batch of ‘Cobalt Blue’ for cone 10 and stoneware clay. I have mixed and used this glaze before and never had problems. However this time, when the glaze dries, it is extremely powdery. It adheres well but I can easily brush off the drips while I would usually carefully shave the drips with a tool. My bigger problem is that when I dip the top edge of my cup in another glaze I usually use, the 2nd glaze cracks and easily falls off. This double dip is a method I have used before and it worked beautifully with the glazes involved. I also tried the 2nd dip using another glaze, with the same flaky results, so I assume the problem is with my cobalt glaze. I did fire a piece with the cobalt glaze only and the color and thickness showed no problems.
Here is the Cobalt Blue glaze recipe:
Custer feldspar 48.2
Gerstley Borate 4.8
Barium Carbonate 4.8
Zinc oxide – calcined 2.4
Tin Oxide .9
Cobalt oxide 2
Any educated guesses as to what I did wrong? Can you suggest an easy fix or is recycle bin my easy fix?
Thanks for all the help those of you share on this forum!