Bruce Gertsch on tue 19 jan 99
Hi Everyone,
I am interested in getting some information on pit-firing that I cannot
find in books or the archive. Hopefully these are not stupid
questions:
1. What kind of clay is best to start with?!? I am a novice and would
like to start with some pre-mix bought at the university (ie c06-04)
without having to alter it, or do I need something super low fire? I
read in Hands in Clay that you can use anything from earthenware to
porcelain (!), is this true? What is a best bet? I hope to start
simple then get ambitious and dig some local up later.
2. Which leads me to my next question: What range of temperatures do
you see in pit-firing? I know this totally depends on your technique,
but can you consistently hit 1000 deg C in a bonfire with a pit of
modest depth and wood +cowpies+sawdust, or is this unrealistic? 500 deg
C? Can anyone give me an example/expections before I go out and char
some clay? I'm hoping to just dig a 2 foot hole in the sand on the
beach, and pile it up. The more traditional the technique (ie
Southwestern Native American, etc.) the better.
3. Can anyone reccommend slips that can be used as a pseudo-glaze? I
had heard of this somewhere. I assume true glazes are out of the
question. Is there any way to waterproof a pit fired vessel (in a
pit), or is the firing temperature too low? Maybe just kiln fire
later.....
4. Can anyone recommend literature on technical aspects of traditional
pit-firing techniques - books or periodicals?
Thanks in advance, I have been impressed with the quality of comments on
this page and hope some of you can help me get started!
Jeff Gertsch
Biochemist by day, potter by night in Honolulu.
Candice Roeder on thu 21 jan 99
Hi Bruce,
> 1. What kind of clay is best to start with?!? I am a novice and would
> like to start with some pre-mix bought at the university (ie c06-04)
> without having to alter it, or do I need something super low fire?
I've used earthenware (both red and white), stoneware, raku, and
porcelain commercially prepared clay bodies. I got the most thermal
shock cracking w/the earthenwares, and the best result with a white
stoneware that had some fine grog in it. Porcelain is lovely and
responds well to color. Brown stoneware that bisques orange worked
fine, too. Try a variety to see which you like best. I like one that
not only fires to a nice color, but is smooth for burnishing...
> 2. Which leads me to my next question: What range of temperatures do
> you see in pit-firing?
I stuck a digital pyrometer probe through a gap in the side of my "pit"
and into the coals. It registered around 1800 F. Easily goes over 1200
F. every time. This was on the cooler outer edge, too, not in the
middle...and after the flame had died down...it was the coals I was
measuring. Pretty hot. I use a lot of wood, though!
> C? Can anyone give me an example/expections before I go out and char
> some clay? I'm hoping to just dig a 2 foot hole in the sand on the
> beach, and pile it up.
Yes, that would work. Again, experiment. For me, since I have about
4-6 inches of sawdust, then pots, then another couple feet of wood, I
need more depth. You want to contain your pots and fuel, and leave room
for air circulation.
> 3. Can anyone reccommend slips that can be used as a pseudo-glaze? I
> had heard of this somewhere. I assume true glazes are out of the
> question. Is there any way to waterproof a pit fired vessel (in a
> pit), or is the firing temperature too low? Maybe just kiln fire
> later.....
Don't kiln fire it later! You'll just burn off everything you smoked
into the pot. You can put a low fire glaze liner on the inside of a
pot, if you wish. Just don't have glazed pots touching, or they'll
become fused together. You can try a sealant post firing, such as
Thompson's water seal (concrete or deck sealer). I like them unglazed
(I use Terra Sigillata) The smoke decorates the pot.
> 4. Can anyone recommend literature on technical aspects of traditional
> pit-firing techniques - books or periodicals?
Smoke Firing by Jane Perryman, and Sawdust Firing by Karen
Hessinberg...both have excellent information, and inspiration for you.
Have fun.
Candice Roeder
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