Corinne P. Null on thu 27 mar 97
In response to the pizza-stone thread,Ron Roy wrote:
>With cone 10 bodies you run into cristobalite problems - especially with
>high iron bodies.
>If there is significant cristobalite present thermal shock cracking is the
>problem at oven temperatures. My dilatometer experiments indicate this
>reversible cristobalite inversion happens between 150C (300F) to 250C
>(480F). It means - if the ware is not placed in the centre then one side
>goes through the expansion before the other side and may crack. There is no
>cristobalite in low fire bodies - not through firing anyway. At come 6
>there is not enough time for the cristobalite to build up much. Either of
>those temperatures would be better.
Geesh, this is scarry! What you are saying is that cone 10 really isn't
safe for oven use above 300F? That cone 6 ware WOULD be safe? Aside from
worrying about the trauma of taking out of the oven a broken casserole and
ruining dinner, I guess I'm also worried about about customer liability.
Also, what about the two different ware handling thermal shock, ie; being
put into a preheated 450F oven, or coming out of a hot oven?
What is the best claybody and glaze temp for this stuff?