aluminum hydrate use when firing lids and bodies together

[Rick Wise]

I think I understood Hsinchuen Lin to say that he was able to fire a lidded jar by painting aluminum hydate along the area where the lid meets the jar -- in other words, to keep the glaze from sticking the lid to the jar when fired.  I often fire the 2 pieces of a lidded jar in place but only after very carefully removing all traces of glaze from the area where they meet, and sometimes they still stick.

Is applying aluminum hydrate a "thing"?  If so, do I just mix it with a little water and paint it on?

 

[liambesaw]

Yes, I mix it with some wax.  It's called alumina or "lid" wax.  A little dab'll do ya, because you don't want it running anywhere, it will ruin any glaze it touches.

[neilestrick]

No, you can't have glaze where the pieces touch, even with alumina. They must be clean of glaze. You put the alumina there to keep the clay from sticking to the clay, which can happen when you're using clay bodies that fully vitrify, especially porcelain.  Mix the alumina with the wax resist used during glazing.

[Min]

1 -2 heaping teaspoons of alumina hydrate to about a cup of wax resist, add some food  colouring so it's a different colour than your regular wax resist so they don't get mixed up. The alumina hydrate settles quickly, need to keep it stirred up while using it.

[Mark C.]

I just dip my wax sponge piece in a bowl of alumina and coat the lid. Then use regular wax on the seat