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Biography: The Designer - Bill Bracker
William (Bill) Bracker (B.F.A. and M.F.A. - University of Nebraska at
Lincoln) was a professor of Ceramic Design at Texas Lutheran College,
Purdue University, and the University of Kansas. While at Purdue
University, he designed a portable Raku Kiln using ceramic fiber (an
innovative new product at that time). He was the first to use
ceramic fiber in Raku kilns and demonstrated his kilns at an N.C.E.C.A.
conference in the 1970's. Continued demonstrations occurred in
locations from Colorado to Virginia. Over many years of testing
and personal use, he further refined his initial designs. The
Bracker Raku Kiln has been constructed for over 30 years in strict
accordance to Bill's design specifications. We feel that this kiln
continues to be the most portable and cost-effective on the market.
Description
It is a lightweight and portable design for firing ceramic pieces in
your own backyard.
The kiln is made by lining a cage of wire fence
material and a metal garbage can lid with one half inch thick fiber
blanket. The fiber is then rigidized with a mixture of sodium
silicate and water. The use of the fiber allows the ceramicist to
have the insulating qualities of soft insulating firebrick,
yet is light enough that anyone is able to pick it up.
For the base of the kiln, you get a case of firebricks.
(Please do not
fire directly on concrete or the concrete will crack.)
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Kit Specifications:
 | Interior dimensions 18" x 24" |
| Propane Burner (torch) 100,000 BTU's/hour (500,000
BTU's/hour also available) Red Dragon, includes shutoff valve, hose, and attachment to
the propane tank. |
| Firebrick for pad rated to 2600
degrees Fahrenheit |
| Burner entry point and exit holes (peep holes) confirm to Fredrick
Olsen's standardization configurations |
| Lightweight and portable design utilizing garbage can lid with top
handle allows for multiple Raku set-ups with only Kiln necessary |
| Made with 1/2" thick, #6 density ceramic fiber (insulation properties
of 3" Firebrick) rigidized with sodium silicate and water |
| Fiber construction provides lower BTU loss than Firebrick which
ultimately results in better insulation, lower fuel consumption, and
faster firings (initial firing in a cold kiln should take less than
one hour. Successive firings should take less than 30
minutes). |
| Can be relined fairly easily and inexpensively |
| NOTE: You CANNOT bisque in this kiln. It fires too fast and
cannot be controlled enough. |
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Set-up and Firing:
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| Use firebricks to create the pad for the Kiln (using 10 -15
bricks) |
| 3 more firebricks are used as post for kiln shelf |
| 2 more firebrick can act as the prop for the burner (this should leave
you with a few extra) |
| Place the pot on the kiln shelf |
| Fiber Kiln is then lowered over the set-up. |
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You are now ready to fire!
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Firing tips:
To avoid thermal shock on the shelf...
On the first firing of every firing session...
- Heat up the kiln slowly.
- Set the flame low and plan on it taking 60 minutes.
For the additional firings
- Set the flame higher and plan on it taking 30-40 minutes.
To get maximum heat out of the torch...
Keep the edge of the burner about 1/2" or so outside
the shell of the kiln. Aim the flame into the kiln. This
gives the flame lots of oxygen to burn.
If it is windy outside, set up a wind block to help keep the heat
inside of the kiln. Or find a less windy part of the yard to
fire in.
Tip: Some people struggle with how to move large pieces without
breaking them. With this set-up you can buy an extra set of kiln
bricks and have two separate platforms. When your first load is
ready, simply move the Fiber Shell and Burner to the next platform, and
reduce your pieces in place.
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Tips, pointers, troubleshooting
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| For those of you wishing to use the 500,000 BTU torch, here are some
tips and information that was written before the introduction of the
100,000 BTU version of the kiln. (This information is
still good-to-know for theory for the 100,000 BTU users.)
Q: Why does the
manufacturer recommend a 100 lb propane tank?
A: To answer, it
helps to understand the properties of propane. Propane is gas at
room temperature. It is inefficient to sell it that way so it is
compressed, bottled and sold as a liquid (LPG) Liquid Propane Gas.
To burn LPG, you must be turned back into
vapor. That can be accomplished by releasing the pressure in the
bottle by opening the valve, and out comes the propane gas. There
are a few complications though.
The rate at which the LPG will turn into
propane vapor depends mainly upon two things, 1) the temperature at
which the propane is changing state from liquid to vapor and 2) the
surface area of the LPG in the bottle.
The warmer the LPG is, the easier it
vaporizes. Additionally, the warmer the vapor is as it passes
though the valve, the less likely the valve will freeze up. (As
gas changes from high to low pressure, it requires heat, so much so that
it can actually freeze up the valve.)
Also, the liquid can only turn to vapor at the
liquid surface in the bottle. The more surface area, the faster
vapor can be created. Bigger tanks, particularly horizontal ones,
have more surface area.
So, the reason a 100 lb tank is recommended is
because it helps keep the tank warmer for the state change from liquid
to vapor. It also provides greater surface area of the LPG for the
state change.
(I hope I have describe this accurately. For
more info see the "Ideal gas Law" and the "First law of
Thermodynamics" in your physics book, or try a Google search. )
Q: I have a
big 100 lb propane tank and I'm still have problems getting the kiln hot
enough. What's wrong?
A: Here are a few
things to try:
- The colder the outside air, the more difficult it is to get
sufficient flow of gas for your tank. Cold weather and/or high altitude
locations can be problematic.
- Windy locations can also cool tank and
the kiln. Try keeping your kiln and tank in an area protected from
the wind.
- Check the safety flow switch on the
torch. It may have become accidentally set.
- When setting up the kiln, locate the
torch about 1" outside the kiln body. otherwise the torch may
not breath well and will burn cooler.
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