Here is one solution I have used for many years.
I too had an old gas oven that needed someone to monitor it as long
as it was operating. It was very inconsistent, especially in the
winter months. Remember that city gas is designed for heating
furnaces not burn out ovens.
With a large cast it was always late in the class scheduling to cram
it all in. Many time we had to cast after the class was over and
another one starting. Many times we have over twenty flasks to cast
in one class. Each student may cast as many as two flasks per class
with a casting class lasting fourteen to sixteen sessions. Casting as
much as possible is an absolute must to start to learn the casting
I replaced it with a 220 volt kiln with a regular rheostat NOT a
programmable one. The dry electrical heat is also, in my opinion, a
cleaner burnout. I also have a small Neycraft one for smaller loads.
What you must find is the dial setting that reached your peak burn
out temperature. I ramp the oven up to 1350 f for the peak
temperature. The control dial on this oven is set at 3.5. The oven
will slowly climb to that temperature overnight. It operates like a
room getting warmer and staying at a set temperature. By setting the
oven on the pre set number it does climb gradually which is what you
want. This process goes through the peak burnout cycle successfully.
I have done this now for over thirty years. Small and large loads
work successfully this way.
I do have a code steel and concrete work bench that is vented so I
do not worry about anything going wrong. If the oven malfunctions, it
would be a wire melting, which shuts everything down. I've had this
happen only twice in over forty one years of casting.
When you arrive for class all you have to do is turn the oven down
and wait for your casting temperatures. Time wise this is ideal
because all the burn out happens while you are gone. By setting the
oven to climb to peak temperature, you don't have to worry about the
programmable control not working properly.
If you go to the Southeast Technical College Jewelry page you will
see my current ovens and casting set up. The spin caster is over
twenty five years old and still works like a champ. A bit beat up
mind you, but a hearty machine.
In fact our casting machine is one of the Lucas Casting machines
750 linked on Orchid. An older unit, but built to last.
Southeast Technical College