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pit fire results - long

updated sun 31 mar 96


John Sproule on tue 19 mar 96

Hi folks,

If you're interested in pit fire stuff we just tried it for the first
time, and I can tell you about it in nauseating detail unless you get to
your delete button first.

The Pit:

4' tall iron (?) barrel from the recycling depot, I don't know what toxic
chemical was in it before, and I don't really want to know. we used a
piece of metal roofing for the top.

The Pots:

A variety, with a variety of terra sigs. Because I'm lazy and cheap, I
used what I had on hand, rather than buying state of the art terra sig
materials. I like to think of it as reclaiming the immediacy of the
ancients :)

There were 2 clay bodies: both Plainsman, M360 and M390, red ^6 throwing
bodies, very smooth, hardly any grog.

THe Terra sigs: slaked versions from each of the clays, one of ball
clay only, one of redart clay only. Again, because I'm lazy and want to
find the easiest way the first time, I used no deflocculant. I slaked
the clays overnight, siphoned off the water with a slip trailer, then
siphoned off the thinnest slip with the slip trailer into a labeled
container and chucked the rest of the sludge. In this process, the
redart clay was the easiest to deal with.

The Application: Inspired by an article on Duncan Ross in Ceramics
Review, I tried sponging the terra sig in layers, with newspaper
resists. I also brushed it on with a hake brush on different pots, several

The Burnishing: Tried spoon method, and plastic method (didn't have
saran wrap (evil stuff) so I used bits of recylcled plastic bag I wrap
pots in. THe spoon method was time-consuming but gave a great lustre,
the plastic method was faster, and gave a duller lustre, but was quite
successful on the redart terra sig. Pots were left out to dry completely.
The pots were bisqued to ^014 in electric.

THe Firing: We literally didn't know what we were doing (isn't that the
best way to learn?!), so we put a layer of scrunched newspaper in the
bottom of the barrel (standing upright), then the pots (small bowls)
upside down on the paper, then kindling (warped 2X6 wareboards I wasn't
using any more (very dry). About 2' of 2x6 all together) and bits of
newspaper, then hardwood sawdust from our woodturner neighbor, then more
newspaper in rolls this time like small logs, and more scrunched on top.
This is all packed in REALLY tight.

We set it on fire and put the roofing on top. the fire went out
immediately, so we set it on fire again, and left the top off. The
roofing covered half of the top of the barrel for most of the firing,
which seemed to work really well, with billowing smoke alternating with
flames for two hours. We hovered over it the whole time, and fussed.

When the smoke had stopped and the flames got down to the kindling, we
put the top on so there was a 2" gap on either side of the roofing for
air to get in. Then we let it sit and smoke a lot. and 3 hours later we
opened it up.

The RESULTS: THe M360 terra sig was cracked like the craqueleur on an
old master painting, but this may be the result of spoon burnishing. Colour
was okay, good blacks, with some very
promising lustrous bits. The M390 terra sig was ho hum. The ball clay
terra sig was gray and as I only plastic burnished it, it showed the
brush lines. Very cool, but gray and black. The Redart was the best of
all, with deep blackening, and rich red where it wasn't black. I
burnished the redart with plastic, but it had quite a nice sheen anyway.
All of them took the black well, and showed real variations. I didn't
notice a difference between sponging and brushing. THe spoon burnishing
had the best sheen.

Recommendations: Try spoon burnishing the redart to get a higher sheen.
Apply the terra sig at leather hard, instead of dry (I tried both on
these pots and that may be the reason for the craqueleur on the M360 -
terra sig applied at almost dry stage). There was no heat cracking or
exploding, which I expect is because I bisqued them first. Try dipping
the pot in terra sig and see what happens.

So there you are. I'm a great believer in "see what happens" so if you
find my methods a bit unorthodox, that's why.


KIM ALLEN PETERSON on thu 21 mar 96

Greetings from windy New Mexico:
Just a note for you folks trying to sawdust fire for the first
time. If you have a barrel, raise it off the ground about half a bricks
width (when laying flat). Put down a layer of dust (hardwood if
possible). Put in your clay. It matters if you use greenware, but
sometimes the result is worth the fragil nature of the piece. cover it
with dust. I would recommend some kind of wire mesh to keep your works
separated, but it isn't manditory. Try to keep a good layer of dust
between your pieces. When you reach the top.. Put a few pieces of
newspaper spread over the top. Light opposite edges of the paper. Cover
it so that a little smoke escapes. The less smoke escaping, the blacker
the finish. Burnished pieces seem darker as well as shinier. I also
recommend a few quarter-inch holes punched in the barrel every six to
eight inches down from each other and about four to five to each layer.
Once your fire has started.. feel free to check the amount of smoke
leaving the "pit" ever so often, but you'll find that you won't have to
check on it very often.
Have fun and enjoy the results.
Kim Peterson
Las Cruces, NM
(For 48 more days).