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salt firing, so many questions

updated fri 10 may 02


Paul Herman on thu 9 may 02

Many questions indeed! I'll try a few.


> So may questions...not enough experience...need help!

I fire porcelain
> with just salt and stoneware with salt, soda ash, baking soda, sawdust,
> borax (maybe too much stuff to be introducing?- though it would give more
> texture and flashing).
Sounds like a lot of "stuff" you're putting in there. I use only salt
and still get various results.

> Porcelain Firing Questions
> 1. How do you keep the lids from sticking when fired in place? I wax them
> with wax that I have added aluminum hydrate to, but they still stick.
Use wads containing sawdust to separate the pot and lid. I use four wads
on teapots, ten or twelve on casserole lids. Sawdust burns out and makes
the clay full of pores and crunchy, easy to tap or grind off.
> 2. What are the black crystal like substance on the floor of the kiln
> coming from the bag area? Is it harmful?
Never heard about any black crystals, maybe it's from all the "stuff".
> 3. Why did a few of the pots on the floor of the kiln look like they got
> burned in spots at the bottom of the pots and slightly up the sides? It is
> like a flash but burnt looking?
Lighter coat of vapor glazing near the floor?
> 4. why did some of my handles and a few spots on pots turn bright white
> while the rest of the pot is gray from reduction?
Spotty reduction?
> Stoneware Firing Questions
> 1. Why did the same blue glaze I used on the porcelain that looks fabulous
> look crazy on stoneware.
Not enough information for me to say. Sounds like a glaze to use on
porcelain only.
> 2. Why do I only get the beautiful flashing and orange color and soda
> buildup that I want on the bottom of pots, not on the sides or insides? I
to find a clay that I do not have to use a slip
> to achieve this look. I know this is possible because I get it on a few
> pots each firing, I just need to figure out how to have this happen more
> regularly. The rest of the pots in the kiln that are natural outside are
> UGLY! creamy with gray specs.
Again, a lighter coat of vapor glaze will give warmer "flashy" colors.
HINT: Given to me by Don Bendal. Take your regular decorating slip and
mix half and half by weight with fine aluminum oxide. Makes gorgeous
colors in salt, resists glaze buildup. Mine works brushed on bisque.
> 3. How do I get plates not to warp? I'm
> almost certain it is the wads and not technique.
Plates!!!! Cursed plates. Use lots of wads or snakes to prop the durn
thing up. Clay gets really soft and flexible at high firing
> 4. same as above... lids sticking? banging my head against the wall!!!
WADS! WADS! WADS! Lots of them to avoid warping.
> 5. why do I get great salt buildup on porcelain and not on the stoneware?
The porcelain probably has a higher silica content, and the stoneware
more alumina.

Good luck,
Hardway Herman