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Info on kilns


#1

Hello orchidians i am new on this site but have been reading post
for at least a month and really love this community.

but now i’m stuck with a little problem and would love to receive
some info… i have just bought a neycraft kiln with an
incorporated pyrometer(not a computer but a manual pyrometer) i dont
realy know if the probleme is with the kiln or with the
investment(satin cast 20) but i cant even do a 6 hour cycle on 2 x 2
flask cause at 700F the investment is burning! i have tried twice
with the ratio 40ml water for 100 gramms of powder but twice the
investement turns dark brown with smoke coming out of the
oven… can someone tell me what i’m doing wrong!

thanks again everyone


#2

Thats The wax burning away which it should be doing… however, you
need to go to around 1350 oF and stay at that temperature until the
flasks are completely white in color and all traces of wax /carbon
are gone… then , you drop to your casting temperature and allow
the flask and oven to stabilize at that temp before casting the
item. Best Wishes,

Daniel Grandi


#3

Dear Sylvain,

EVERYONE will tell you what you are doing wrong. But the fact is you
are doing nothing wrong. You aren’t going through the whole cycle.
The wax burns out of the flask during the process and turns black as
it burns out. As the temperature ramps upward the flask will hit
higher temperatures to make all the smoke and ash gone. At about 1350
F the flasks will get a dull red. When the flasks are cooled to
casting temperature they will be white. Depending on the oven load
this can take up to twelve hours. With one or two flasks a six to
eight hour cycle should work fine. Here’s a suggested temperature
ramp. First two hours get it up to 700 F. Second through fourth hour
go to 1300 to 1350 F no higher. Leave it there for two hours. Drop to
casting temperature and wait one half hour. Time to cast! I leave my
Neycraft on control setting 3 1/2 when I leave at night. 3 & 1/2 on
my Neycraft will give me 1350 F and then stay there. In the morning I
come in and turn down to casting temperature.

Good Luck,

Todd Hawkinson,
www.trhawkinson.com
T.R. the Teacher
www.mctc.mnscu.edu/jewelry


#4

Fear not. The investment is not burning. The wax in the investment
molds will start burning around 700 degrees. It is not a complete
combustion process at this time so the wax is very sooty. Continue
increasing the temperature until you reach around 1300 to 1350
degrees. If the oven is full of flasks you may have to leave the
flasks at that temperature for a while until all the investment is
white.

Around 1000 degrees the smoke from the burn out oven may have a bad
odor. Make sure you have adequate ventilation around the burn out
oven. Good Luck Lee.


#5

That’s normal for a burnout. The wax inside the investment burns
out, causing smoke, and turns the investment dark colored with
ash/residue. As the burnout continues, that residue burns off and the
investment becomes lighter colored again. I was told that’s how to
tell when a flask is ready to cast–when all the dark residue is
gone, and the bottom of the flask is white again.

–Kathy Johnson
Feathered Gems Jewelry
http://www.featheredgems.com


#6

There are a couple of variables about burnout that have not been
entered into the equation. The length of burnout is highly variable
for two reasons: One is the fact that small flasks do not take
anywhere near the time that is required for larger flasks and the
other is the temperature rise capability of the oven. I use very
small flasks ( 1 1/2" x 2" copper pipe couplings. My oven has a
control for rate of temperature rise. My first cycle is at a slow
rate of temperature rise…one hour to get to 500 degrees F. At
this point I remove the wax absorbing piece of Hardy board, turn the
flask over and ramp the temperature rate of rise to the highest
setting. This takes about an hour to arrive at 1325 F. I bathe the
flask at this temperature for thirty minutes and then cool down to
800 F and proceed to cast. I did a fifteen gram gold band on Friday
and the total elapsed time was 2 1/2 hours. It turned out
beautifully. By the way, I now use distilled water to mix my
investment. Since it comes out of the plastic container it has not
been subjected to the aeration that results from using the sink spout
and I don’t have to worry about the potential effect of unknown
minerals ,sediment or chlorine.

Ron at Mills Gem, Los Osos, CA.


#7

Sylvain I don’t think you have done anything wrong. At 700 degrees
the wax has melted and the carbon residue is burning out. It is
when it reaches the 1200 degree stage that the investment goes bone
white. Tim McCreights book “The Complete Metalsmith” gives a good
basic description of what is occuring at each stage of the burnout
process.Familiarizing yourself with the steps lets you know what to
expect and lessens the feeling of "Is this going the way it should?"
Believe me, the first time I used my kiln, I sat there the whole
time checking at each stage of the process, wondering and worrying.

Brigid Ryder