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glaze spitting cobalt

updated sat 8 nov 03


Gene and Dolita Dohrman on thu 6 nov 03

Just a thought here. I have a some experience painting with a concentrate
of cobalt oxide on a commercial glaze called 'Colonial White'. One of the
things you have to be very careful with is that nothing touches the surface
after it is dry. Even a strong breeze can pick up some of the cobalt dust.
I transferred a plate from my house to the studio in my bike basket and
could see the specks that were blown onto the white glaze. One tiny
particle that cannot be seen by the eye will show up blue on the white
background when fired. I watched an artist in our studio paint an intricate
dragon on a lamp base she had thrown. Every day she would cover it with
plastic. This was the worse thing she could have done. When it was fired,
you could see where she had pulled the plastic on and off, the cobalt dust
ruined the details completely. She went ballistic when it came out of the
kiln and tried to blame the guy who fired it. I learned from her mistake.
Louisville, KY

lili krakowski on thu 6 nov 03

I have no idea what the problem is, because I am having trouble =
visualizing the problem. Does the cobalt in and of itself pop off the =
glaze? Does the glaze on which the cobalt is painted fall off?

My impression is that cobalt has a high melting point,in which case it =
may just be sitting on the glaze rather than melting enough to sink in. =
My inclination then would be to add a little flux to the cobalt mix.

I would suggest also that you try painting with cobalt carbonate and see =
what happens.