I have been vacuum casting after burning out in en electric burnout
oven since 1974.
You will find there are many approaches to lost wax casting of
metals.
You will fine that in most cases all the processes described will
work. The best process is the one that works for you.
I cast outside on my patio.
When the weather is mild I put the flasks into a cold burnout oven
three hours after investing. In the summer when as it is drier the
flasks go into the oven about 2 hours after investing.
I tried placing the flasks in a 250 degree oven but found by the
time I installed a full oven full of flasks the temp was greatly
reduced.
I normally have flasks from 2.5 to 5 inches in diameter in the oven.
The smaller flasks normally contain pink injection wax and the
larger flasks might contain up to 500 grams of Blue Ferris carving
wax. I heat to 300 degrees and hold for three hours. I than raise the
temperature up 250 to 300 degrees per hour until the oven temp is
1330 degrees.
I let it set at that temp for 8 hours. I feel that hold temperature
is necessary as I fill the oven to full capacity. I may stack the
2.5 inch flasks.
IMPORTANT. If you are vacuum casting sterling silver or gold with
copper alloy check out the paper I wrote on fire scale free casting.
The paper is listed in Orchids Tips From the Jeweler Bench. The
process is simple and prevents fire scale from forming on gold and
silver. Sterling is cheaper than the fire scale metals and the
process doesn’t cost extra money or time.
Lee Epperson