Burn-out cycles

All of the burn-out cycles I’ve seen…5 hour for example: 1 hr. -
300F, 1 hr. - 700F, 2 hrs. 1350F, 1 hr 800F (±) = 5 hrs total

Kerr suggests no temp change faster than 9 degrees per minute.
Therefore, to ramp from 300 to 700 would require 44 minutes, 700 to
1350 - 72 minutes.

Where are the ramp minutes in all these published cycles?

If the Kerr Tech rep. is correct - careful “ramping”; that would
make these referenced burn-out cycles look a lot like my Grandma
Hildigard’s oatmeal-raisin cookie recipe…a pinch of salt, a slurp
of vanilla…whatever!!! Like…turn off the kiln at 1350, go have a
cup of coffee, check your email, come back and cast - skip the “email
check” on cloudy days.

Am I missing something?


Speaking of burnout cycles, How about the best for RP resins?


5 hour for example: 1 hr. - 300F, 1 hr. - 700F, 2 hrs. 1350F, 1 hr
800F (+-) = 5 hrs total 

We have a heavy duty timer wired into the circuit. We put flasks in
the kiln at 5 or 6 pm, which gives them a good 6 hours to cure. The
timer comes on at midnight. We turn it down when we come in at 9 am
or so, let it soak till noon or something, and we cast. We’ve been
doing this for 20 years, hundreds of flasks, with fine results.
Another thing that doesn’t need to be agonized about, and I’ve
discussed this with someone from Kerr before, too. He just shrugged,
like “yeah, fine…”

For the 2.5 and 3 inch flasks I have been using, My kiln programmer
only will do two steps, but this seems to work just fine. I start at
room temperature. I set the kiln to rise at 7 degrees F per minute
to 1350 F and hold for 2 hours. Then temp is reduced to hold at
casting temperature of 900 to 1000 F depending on the metal and size
of the pieces. Thin sections and higher karats of gold need to be
hotter. I have it set up to be ready to cast first thing in the
morning, but set to hold at temperature all day, just in case
something comes up and I cannot get started first thing.

I have bought a larger and more sophisticated kiln that I have not
used yet. The plan there is to steam out the wax and then put it in
the kiln preheated to 300 F and then burn out in a slower cycle for
bigger flasks.

Stephen Walker