Linda Mosley on sun 28 may 06
Hi Donna,
This is an interesting way to learn about firing. The
basic concept of my greenware-firing method in a
trashcan is to heat the greenware slowly in a central
core area by burning the outer ring first.
Sawdust-firing is not a clean bisque, but you might be
able to achieve that by using a clay saggar (tube or
box of coarse raku-type clay) for the center chamber
rather than a metal mesh tube, to prevent reduction.
[Note for beginners who might read this: always be
safety-conscious. Abide local fire codes; fire in a
well-ventilated area. Wear heat-resistant gloves and
apron. Have a water source or fire extinguisher ready
for emergencies, and remember that water + high heat =
dangerous steam.]
Prepare 2 combustible mixes:
Mix #1: For outer ring, mix coarse woodchips or
shavings/shredded paper plus a few pieces of charcoal.
Mix #2: For inner chamber, mix about 1 part charcoal
to 3 parts mix of fine sawdust and finely chopped
corn-cob chips if you can find it (found at pet store,
for small animal bedding).
Prepare trash can:
Drill 1 inch holes all over garbage can, about 6
inches apart, or dry stack a chamber of firebricks.
Create a center "core chamber", about 8" in diameter,
by rolling metal hardware cloth into a tube that will
hold the greenware. (Optional: cut “shelves” from
hardware cloth that can be hooked into the tube as the
greenware is loaded, to keep pieces from settling onto
each other as the sawdust burns away.) Place the wire
tube in the center of the garbage can, and in the
outer ring place 3 crumpled wads of newspaper with
"wicks" sticking out through the lowest holes, to
start the fire from the bottom later.
Load greenware and combustibles:
Fill the outer surrounding chamber with mix #1. You
will need to experiment with your particular materials
to get the right amount of air space in the mix for a
slow and even burn.
Layer the greenware inside the inner chamber with 4-6”
combustible mix #2, starting with combustibles at the
bottom. Hook hardware cloth “shelves” in if needed.
Options:
If you want colors, wrap each greenware piece in a
paper bag or newspaper bundle with oxides, Borax
(flux), Brillo-pads (flux + color from metal), etc.
To Fire:
Prop the garbage can lid on loosely with bricks. Light
the outer ring of combustibles through the 3 holes
where you put newspaper wicks. It should take about
12-24 hours to burn completely and only a few inches
of ash will remain.
For general information on kilns and firing, please
visit
http://users.stlcc.edu/lmosley/Firing/index.html
Enjoy!
Linda
Linda Mosley
Studio Potter & Teacher
lmpots@yahoo.com
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