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Jewelcast Kiln


I recently bought a very gently used “Jewelcast” kiln and associated
casting apparatius. My first task is to determine approximate
temperatures. All it has to control it is a knob with Lo, High, and a
few numbers in between.20 The Tim McCreight book tells me that
aluminum can be used to determine burnout temperature. It curls at
1220 degrees F. Any other hints for calibrating the temperature range
roughly? I want to use it for: annealing wire granulation (???)
casting - I have a lovely little enrolled trilobite named Freddie The
Flexicalymene who needs some silver clones. Thanks, Karen


Hi Karen, I am sure there are people on here who know far more about
this than I do. Some years ago I did a little pottery for recreation.
I think the cheapest option would be to find a potters or ceramic
supplier and buy some pyrometric cones. They are made from various
mixtures of alumino-silicates and fluxes and melt at specific
temperatures. If I remember rightly you use 3 cones, one lower, one
the right temperature and one higher. They bend over when a certain
temperature is reached. The first and third cones are warning cones. I
believe the other way you could go is to buy a pyrometer which would
measure the temperature. As I say I am sure some of the casting or
enameling guys will know more than me.

Chris Hackett



For this kind of kiln the different numbers are not specific
temperatures but rather variable percent times it is on or off. You
need a pyrometer which is a temperature gauge to tell how hot it is.
Pyrometers cost about $60 at Arrow Springs or Franz Bead and I’m not
sure how much at Rio Grande. Rio Grande also sells little ceramic
tablets you can put in the kiln and which melt at specified
temperatures to use in calibrating the pyrometers. These work on the
same principle as ceramic kiln cones.

To callibrate a pyrometer for glass annealing the technique is
similar. One would place a rod of the desired glass horizontally with
one end supported and anchored between stacked firebricks and the
other end unsupported. Then with the kiln slowly brought to annealing
range there will come a time when it will bend and the free end will
sag down. At the temp when it bends an inch in 10 minutes you have a
temperature about 40 to 50 degrees farenheit above the annealing
temperature of the glass in question. Usually you have to repeat it a
few times to make sure you catch the right temp. I still keep a
handful of bent glass rods from the last time I calibrated my kiln so
visitors to my workroom have something to wonder about. Geo.


Karen, People who make ceramics have little cones that determine
temperature. Each different cone melts or bends at a specific
temperature. I bet they are relatively cheap. Look in your yellow
pages under ceramics or pottery. You probably can find someone who
has a studio and teaches classes and sells supplies as a business.


Karen - I don’t know the specifics, but ceramicists use numbered
cones to tell the temperature of their kilns. You can get an
assortment of these, which have pretty precise temperatures for
melting (they slump into little puddles), line several up in your
kiln, set it at a certain number, and leave it. After a couple of
hours (I would guess 2 or 3), turn off the kiln. The max. temperature
for that setting would be determined by which cones melted.


Any other hints for calibrating the temperature range roughly? I
want to use it for: annealing wire granulation?

Fine silver can be used to calibrate your kiln. Since fine silver
melts at 962C or 1763F you can place a small piece of silver in the
kiln set your dial at one of the higher marks, let the temp. run up,
and check for melting. You can then move the setting up or down until
you zero in at the setting where the fine silver melts Hope this
helps. There are also cones used in ceramics which melt at
specific temps. These can also be used fo calibration. JZ Dule


Hello, Try some pyrometric cones like the potters use. Then are like
little obelisks leaning to one side like the leaning tower of Pisa,
and when they reach a certain temperature the top curls downward. You
can get different cones that will bend at several different
temperatures from 1085 degrees Fahrenheit up to 2,475 degrees. You
need to make or buy a little ceramic or wire base to hold the cone
upright on the floor the kiln.

I got some from Ceramic Supply of New York and New Jersey, Inc.,

phone 1800-723-7264, but that was back in 1993 so who knows if they
are still around. Also try Standard Ceramic Supply Company on, phone 412-276-6333. The last I
heard from them was in April 1997. Any other place that has stuff for
potters will have those cones. I hope this is useful. Len Carlson


Hi Karen, Does your kiln have a spot for a pyrometer? Gracious, its
been a long time since I worked with kilns----is that how you spell
it? At any rate, if there’s a peep hole anywhere that will let you
see the temps on the pyrometer, that’s one idea. Mile Hi in Denver
carried several different models a few years back. Unless things
have changed in the last 3 years,
they “speak” kilns fluently


One problem I thought of in callibrating these kilns is that there
needs to be a sufficient time allowed to reach thermal equillibrium
inside. If you just crank it up on ‘high’ or sometimes even on ‘4’ or
’5’ to the target temperature there isn’t enough time for the heat to
dissipate fast enough before the pyrometer reaches target temp. I had
a bunch of saggy half melted beads until I learned that. Geo.


I am no ceramists, but talking to my ceramics instructor, as she was
firing two kilns using cones and pyromter. She emphasized that the
cone action is based on temperature over a period ot time, not only
raw temperature. Also, the oxidizing / reduction characteristics of
the kiln also affects cone reactions. As I understand it the cones
are made of glaze components and is that is what the ceramists is
wanting to know about. hope this helps! efw


This is a good system for calibrating kilns in the upper temperature
ranges. For lower temperatures, I’d recommend finding a local tool
company of the sort that supplies machinists. Ask them for a range
of “tempil pellets”. These are used in heat treating steels for
tempering. They are about the size of aspirin, and melt at very
specific temperatures, from 120F on up. There is an equivalent
"tempil stick" available too. These are like chalk sticks. When you
have, say, a 1200 degree stick and you rub it on something that’s
1100 degrees, it makes a dusty mark like chalk. If the article is
1300 degrees, the stick will melt against it, leaving a liquid mark
like paint. I don’t have the literature handy (I am organizationally
challenged!) but if you go to, the blacksmiths site
will have links to companies like Centaur Forge, and you can follow
to there and inquire. By the way, Rio Grande has the temperature
calibration pellets too, just a much more limited range of

David L. Huffman