Partially burned-out flasks

My kiln is officially dead. I messed with it again today and, as the
saying goes, the lights are on but nobody’s home. The light on the
front comes on, and it clicks like the thermostat is going on and
but it doesn’t even start to warm up. RIP Kerr 666…

There were 4 flasks in it when it quit working. They were thoroughly
steam de-waxed before I put them into the kiln. It appears that they
partially burned out before the kiln started cooling off. The
investment isn’t white, but it’s cleaner than a flask that just
started burning out.

My question is–if I keep these flasks still and don’t move them
until I can get a new kiln, will they still be usable later? Can I
start the burnout over when the new kiln gets here, and cast them, or
are they ruined from getting cold in the middle of a burnout?

Kathy Johnson
Feathered Gems Pet Jewelry


This is a question from which you will probably elicite many
opinions, however, this is my experience.

Flasks can be burned out more than once! In face, when burning out
organic items such as pine cones, star fish, leaves etc, I normally
burn them out at least twice…sometimes three times. Wax can also be
burned more than once. Sometimes a student will not call and notify
me they will not make class. Their flask will be in the oven along
with a dozen others. I simply shut the oven down and allow the flask
to cool inside. Next week, I run it through the entire cycle again
and it will cast normally.

Hope that assuages your fears. Cheers from Don at The Charles Belle
Studio in SOFL where simple elegance IS fine jewelry!


I am sorry to hear of your problem and hope that it all works out. I
have cast thousands of flasks over the years and never had the
problem you are having so I am not sure if you can salvage them.

One thing I do know is that if the burn out was not complete, in
other words you did not remove all wax and carbon from the flask,
then you will most likely have bad castings when you try to reheat

The Investment should have a moisture content when burnout begins so
that steam will help force out wax and carbon and keep it from
penetrating the porous Investment. If a flask is poured and then let
sit for several days it is recommended that you dunk the flask in a
bucket of water before beginning burnout but since you already
started the process I don’t think this will help and instead may
cause additional problems.

If the burnout did in fact remove all the wax and carbon and left a
white color Investment then it may be worth a try to reheat and
complete the cycle.

It is amazing how forgiving casting can be if you have the flask at
the right temperature and use the right torch flame when heating the

Greg DeMark

Good Advice regarding the kiln components. One more recommendation…
when you get a new one or repair your existing unit you can check or
calibrate the thermocouple and temperature indicator by setting the
temperature to 212 F or 100 C waiting until the set temperature is
reached and placing a metal pan or cup of water in the kiln. The
water should boil within five to 10 minutes depending upon the wait
out the water and pan.

Your flasks also need the handle differently. There are two schools
of thought. One says you should soak the flasks in warm water for
five to 10 minutes before placing them back in the oven. The other
says, just place them back in the oven. In either case rerun the
entire burnout cycle. The should minimize any cracking that might
occur. In any event, handle the flasks carefully as they probably
have not reached their full strength. In addition, you should be very
careful, while casting these flasks. There’s a chance that they are
cracked and could run out. Don’t be too disappointed. If these flasks
exhibit significant flashing.

Hope that helps. Good Luck.

Paul Finelt

I once had a student pull out a partially burned out flask that had
sat in his locker for a year and we put it through a normal burnout
cycle and it cast just fine. I certainly would not recommend it as a
standard practice but it worked that time. So just run them through
a standard burnout and give it a try. What do you have to loose?

Good luck,

James Binnion
James Binnion Metal Arts


Thanks to all who replied to my questions about the deceased burnout
kiln and the half burned out flasks.

I purchased a new kiln, a Sierra 1100. I was going to just get the
old kiln fixed, until I stumbled on this one while I was in CR Hill
asking about repairs to the old one. It was a bit more than I’d
planned on spending at the time, but that’s why I have a credit
card–instant business loan when I need it.

I really needed a larger kiln anyway. The old one can only handle 4
flasks at a time. I don’t cast every day, but when I do cast, it’s
usually 12-16 flasks worth of charms. The new one will save me a lot
of time, as it can hold at least 12 flasks per burnout. I could
almost fit the old kiln inside the new one. And it’s got a
programmable controller, so I can set it up and do other things while
it works, rather than babysitting it. Now I just need to get it out
of the car and into the house! The store loaded it into the car for
me, but it weighs 90 pounds in its shipping crate, and I can’t move
it alone. My husband is in Florida hoping to see the shuttle to
launch tomorrow, so it may sit in the car until he gets home this

My first project once it’s in the house and set up will be to try to
finish burning out those partly burned flasks. Like a kid with a new
toy, I can’t wait to try it out!

Kathy Johnson
Feathered Gems Pet Jewelry