[TJR]

I just got a bunch of pots out of the stoneware gas kiln in time for a Mother's Day sale this weekend. The mugs which were made out of porcelain stuck to the shelves slightly and pulled away leaving small chips out of the bottom. The stoneware pie dishes which are larger and take up a much larger area did not stick. Why does the porcelain stick? There was no glaze on the bottom.
TJR.

[bciskepottery]

It's called plucking and porcelain is more prone to that at high temperatures. Mix some alumina with wax and apply to the bottoms of your porcelain wares; the alumina -- which will not melt at high temperatures -- will help prevent the porcelain from fusing to the shelves.

[TJR]

bciskepottery, on 08 May 2012 - 09:01 PM, said:

It's called plucking and porcelain is more prone to that at high temperatures. Mix some alumina with wax and apply to the bottoms of your porcelain wares; the alumina -- which will not melt at high temperatures -- will help prevent the porcelain from fusing to the shelves.

Thanks for the tip. I use Alumina Hydrate for lids. The problem with alumina, is that it is difficult to remove from the lid galleries. I guess I could wash my kiln shelves with alumina-expensive though. Plucking, eh? I know another word that rhymes with pluck.
Tom.

[Denice]

I get some plucking with my stilts and I only fire to C6, maybe next time I clean them up I'll coat the ends with some alumina hydrate. Denice

[TJR]

bciskepottery;
Now I am thinking that the alumina idea is doable. I wax the bottoms of my mugs anyway. I could put a watery thin layer of alumina before I wax. I do like the look of my glazes on porcelain, so I don't want to give it up. Ain't pottery grand? I learned something new today and I am a hard-bitten old dog.
I humbly thank you.
TJR.

[Mark C.]

TRJ
you can also add alumina to your wax-or if you hot dip touch them into a flat pan of alumina powder as it sets off-this uses a lot of hydrate
Another way I wax is to use a piece of cut sponge and dip in wax (water based mobil wax) and dip the sponge in hydrate before waxing pot bottom
That leaves enough alumina to keep the lids from sticking or plucking.
I like washed shelves as thats easier with the alumina in the wash.Hope you got my PM-I was away at show 5 days.
Mark