Imzadi Donelli on tue 9 oct 01
Just did a saggar firing workshop in which the kiln and the saggar was a
garbage can. The morning of the workshop, my instincts told me to read up on
every available info I could find in the Clayart archives on how to do a
saggar firing and do what you guys suggested. (Like keeping my pieces away
form the sawdust unless I want mostly black; and not packing my can very
tightly.)
As a result, MY pieces were the best in the whole workshop and the only ones
with any "saggar" type look to them!!! My pieces were the only ones which had
creamy whites and flashes of pink and peaches, slight mottled spotting and
the copper horsehair effect. Everyone else's pieces came out variations of
mostly black, greys, and small patches of white. Absolutely no flashes of
colors even though they, like me, sprinkled copper carb into the cans and
soaked the sawdust in copper carb and water. They were told by the instructor
to pack their cans and pieces tightly with the sawdust. (I did tell them what
I had read about the sawdust as we were packing our cans. No one believed me.)
***Thank you everyone here at Clayart for all the help and past experiences***
In showing my pieces to other potters outside of the workshop, these people
now want ME to lead them in a garbage can saggar firing. Although I am far
from an expert, they are hoping to even just get similar results to what I
got. And I just want to experiment and play some more and refine this
technique! I love not having to have a ceramic saggar box or find someone who
will allow me to saggar at all in their kilns.
Now for the technical questions:
The instructor had everyone else punch many holes throughout the floor, all
over the walls and the lids of the cans. Having read in the archives, you
want as little air as possible, I only poked about 8 holes along the bottom
perimeter of the can. I, did however, leave the garbage can lid cracked ajar
on the can to allow air in. I was afraid that if I had a completed sealed
can, I wouldn't get much of a fire in the can and no not much of the
combustibles would flame with the lack of oxygen. I told the instructor, I
think my lack of many holes is key. However, he says, he thinks the lid being
ajar and letting in even more oxygen than what they did was key.
Am I correct in assuming that with all the holes in their cans, they
basically just smoked their pots? The fire in the cans drew in oxygen to
simply create smoke. Since the cans are the kiln as well as the saggar, their
was no reduction at all created in their cans. Hence, no copper flashing?
When I do another firing, do I need ANY holes in the bottom of my garbage
can? Should I still leave the lid ajar? Or will there be enough available
air in the can to burn out the combustibles? Assuming that the lid does not
make an airtight seal, will the air being sucked in through the lid cracks be
enough oxygen to continue to burn the combustibles while maintaining a
necessary reduction environment needed for copper pink colors.
I know a (traditional) saggar firing ceramist who gets wonderful EVEN blush
pinks throughout her pieces You'd think she had painted the clay with a
copper wash after terra sigging, except everyone I talked to says she does
not do this. Just sprinkles the copper carb and kosher salt throughout. I had
wet my hands and rubbed on some copper carb into the pots right before
firing. (yes I know this may be unhealthy). I think most of the copper fell
off the pots anyway as it dried in the can. I got only a quarter size
flashing of the blush pink I am talking about. Anyone know how to get a more
even pink? (The ceramist is unavailable for questions and advice until the
spring due to health reasons. Spring! I hope to do about 4-5 more saggar
firings before then.)
Also, what cone should I bisque to? These pieces were bisqued to cone 016,
which I believe is way too low for any kind of reasonable durability. We used
Cone 10 B-Mix clay. But since we don't really know the temp the pieces were
fired at, just burned a lot of wood (like a garbage can bon fire) and kept
the fires stoked, flames shooting above and around the piles of cans. Is this
really low bisque necessary for any color absorption for this kind of firing?
Am I wrong about this? Is there a way to perch a cone to in the middle of the
fire? Would this even work, or is it not necessary? Total firing took about
two and a half -- three hours.
Also, the instructor had the cans still firing for about half an hour AFTER
any sign of smoking came out of the cans. Is this necessary? I read the
hotter and longer the firing, there is more possibility for the colors to
move through and out of the pieces.
Thanks in advance for any info, theories (will test them all) or suggestions!
Imzadi
CMG on wed 10 oct 01
Before I dug my pit I fired in a garbage can in a similar way. Firebox on
the bottom with semi large vent holes. We bolted the cut out pieces back in
place so we could half crack or open up all the way the vents for what kind
of a fire we wanted. For the actual firebox I put a few bricks on the bottom
that supported a metal screen shelf, above that sawdust, pots packed in
sawdust and then the usual sprinkling of copper carb and rock salt, maybe
other things tossed in just for fun.
I bisqued to cone 06, I use a kenzan porcelain and that bisque temp works
really well. Strong enough for handling, not tight enough for the smoke to
not permiate. Get lots of pinks, reds, nice blues. Or got a can full of
yuck that needed to be refired low to burn off all that carbon.
My old can finally gave way, it served me well. It was a fifty gallon drum
that just rusted away, poor thing. When it was in it's prime though it was
fired hot, quick and produced some excellent peices. I, like you had few
vent holes, in fact just the two, with a lid I could adjust too for the
later part of the firing. Now I fire in a big pit, so simple, no tending
the fire so intensely, pack it with so many more pots....really fill it up.
Even temp throughout too.
As far as using wet hands to coat your pieces with copper carb....bad idea.
Use latex gloves. They may not last very long but your health will, that
stuff will make you sick. I wear a mask when I'm using it and don't let
anyone around the pit when I'm throwing it in. I know, I know sounds like a
mom, now wear your gloves, wear a mask, don't breath that in....
You had mentioned some paper bag sagar, did you find that in the archives?
I'd be interested in trying that
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