Expert: Sam Kelly - 8/10/2008

Question
Although I used a wax resist to prevent the glaze from touching on a lid and bowl set, the two pieces stuck together during firing. What is the best way to attempt to separate the two pieces without breaking either the lid or bowl?

Answer
Hi Jennifer, What I use is a kiln shelf prop(never a hammer) and gently tap around the outside of the pot where the lid meets the pot, if you can see there is glaze between the pot and lid then it's usually hopless to persist. If the lid starts to release it's self you will hear the taping noise go to a duller noise, go carefully from here on.
If no success you can sit the pot without covering the lid in very hot water for 30 seconds or so or put it in the freezer for a couple of minutes and begin tapping again, if none of this works then the lid is probably sealed to the pot on the inside.
To help with this problem next time you fire add a little calcined alumina to the wax(not hot paraffin wax), use 100 mesh, it's a sand like consistency. You don't need very much and its best not to use to much as it does not melt in the firing so as the wax burns away the calcined alumina remains separating the two pieces, excess particles could drop into the glaze and you would be able to see them. Do some testing