The 1225 C according to my cone chart is Cone 6 ... I thought that the Keraflex was cone 10 ( 1330 C) . or have they come out with a Cone 6 version ?
If you have fired it only to cone 6 , it will be underfired.
You should be able to lay them flat on the kiln shelf as long as they are not glazed. The cone 6 clay pieces I make are unglazed on the back and I lay them straight onto my kiln shelf with no problem ( as long as I am careful to not get any glaze on the back ) .. . I just checked the Keraflex website and it says this:" Simply fire straight up to the full temperature of 1280°C/2335° (cone 10) once this temperature has been attained, you can switch the kiln off and allow to cool as usual. It is recommended that you use cones to help gauge the top temperature, as Keraflex does need to attain the full 1280°C/2335° (cone 10) to be fully vitrified." ....
Marci >^..^< (x 8 )
sign for for the free mailing list at www.PPIO.com