pre-mixed dry glazes

[artgecko]

Why oh why are my results coming out so poorly by firing to cone 6 with a hold of 30 minutes?

[Andy Clift]

On the first two pieces the glaze application is too thin, and were the round plate forms on the bottom shelf of the kiln?
Also it looks like you are using a very coarse clay body, what is it called?

[Barbarah]

I'd agree on the first two photos. Application is too thin.
Are you painting it on or dipping?
What brand of premix are you using?
I have found several commercial pre-mix glazes work better at cone 5 than at the stated cone 6.
The massive pitting on the plate looks severely over-fired, you might want to put a cone pack in next firing to double check your cone accuracy if you are relying strictly on your comp read out.

[ceci97439]

I agree the first piece is too lightly glazed. The plate however looks over fired. The 30 minute hold seems excessive. I read somewhere that a hold of 15 minutes or more will actually take you to the next firing ^. So if you were firing to ^ 6 you actually went to ^ 7. You may want to fire to ^5 with a 10 minute hold. Hope you find a resolution.

[HIgaki]

According to the people @ Coyote, their ^6 glazes should be fired to ^6 if you are using a kiln-sitter-type kiln. If you have a kiln with an electronic controller, fire to ^5 with a 15 min soak to get the same heat work. Laguna advises along the same lines, although their commercial glazes are listed as ^5.