On many occassions I have had little to no time to do a job for a
client and so I have done a 2 hour cast. I cross my fingers each time
but to date I have had continued success. This is not the proper nor
the best way to do casting but in a pinch it is good to know it can
be done. I dry the investment for 20 minutes and then into the oven
and raise the temperature up to 900- 1000 degrees and hold for one
hour. I cast with a centrifical machine. I only do one item at a time
when I do this. I do not know the results if there would be more
items than one in the flask or if you are doing more than one flask.
I have done this quick cast for more than twenty years, so I know it
works.
It’s all in the steam. When I was told about this method, I thought
it was some sort of fictitious urban legend and refused to try it
for months. I tried it successfully on a Christmas Eve emergency and
used the method for every casting after that for many years, with
both original hard carved waxes and injected waxes. The only
drawback I ever had was when I was casting seven or eight 7" flasks
in one burn out and fried a coil in my oven with the steam. It
especially was nice when electricity costs in San Diego, where I was
at the time, went through the roof.
This will sound crazy, but try it once, I guarantee it will work.
Here it goes…after investing (with no special investment) let the
flask sit for 20 minutes or so. Take off the rubber base and
submerse the entire flask completely under water, under your
bell-jar, vacuum at 30lbs. until the bubbling almost stops, (about a
minute or two). Place the fully saturated flask in a 1350-1400
degree oven and hold for about an hour, or until the sprue hole is
clean and white, (often less then an hour), turn off the oven and
open the door, drop the temp to the desired casting temp, close the
door and hold for a five or ten minutes(depending on flask size)and
cast. Heavy or light, white or yellow, 14 or 18k, you will have a
perfect cast piece in less then two hours.
I know, it goes against all that I have ever learned, but it really
works.
I just used this method originally posted by JD in September. I
thought I’d post my little testimonial.
I cast 3 flasks - silver, 18ky and 14kpd white gold - all of them
came out beautifully. thanks, Miche
It's all in the steam. When I was told about this method, I
thought it was some sort of fictitious urban legend and refused
to try it for months. I tried it successfully on a Christmas
Eve emergency and used the method for every casting after that
for many years, with both original hard carved waxes and
injected waxes. The only drawback I ever had was when I was
casting seven or eight 7" flasks in one burn out and fried a
coil in my oven with the steam. It especially was nice when
electricity costs in San Diego, where I was at the time, went
through the roof.
This will sound crazy, but try it once, I guarantee it will
work. Here it goes...after investing (with no special
investment) let the flask sit for 20 minutes or so. Take off
the rubber base and submerse the entire flask completely under
water, under your bell-jar, vacuum at 30lbs. until the bubbling
almost stops, (about a minute or two). Place the fully
saturated flask in a 1350-1400 degree oven and hold for about
an hour, or until the sprue hole is clean and white, (often
less then an hour), turn off the oven and open the door, drop
the temp to the desired casting temp, close the door and hold
for a five or ten minutes(depending on flask size)and cast.
Heavy or light, white or yellow, 14 or 18k, you will have a
perfect cast piece in less then two hours.
I know, it goes against all that I have ever learned, but it
really works.
All I can figure is that it's all in the steam.
JD
I tried this method and followed the instructions exactly, with
disastrous results.
I had a flask exploded and hit the door on my oven. I am reluctant
to try this again, because had the flask hit a heating element it
surely would have broke it. also I heard a bang in the oven so I
opened the door and it exploded again sending hazardous silica
investment dust into my shop. It took a half day to clean it up.
Robert L. Martin
Goldsmith/platinumsmith
Diamond setter
I have used small flasks 1 1/4 in. waite for 5 min after gloss of
carefule remove the base put in cold over jack the heat up 1 1/2 hr.
cool to casting temp and cast. No stones!
I am glad to see your testimonials on what I have called “Fast
Burnout” in my book. I have been using a short, high-temperature
burnout for about 5 years when I teach casting. This approach was
suggested to me by the retired Director of Research at Ransom and
Randolph. He told me that the key to success was keeping the flask
moist just as you do. He pointed out that a partially dried flask
might crack or even explode. I have had only one so-called explosion
when a student used excessively thick investment and I believe it
left cavities that filled with steam during early burnout and blew
investment all over the oven. No real harm done, just a mess.
Most casting protocols are cookbook-like and don’t explain what is
going on. The objective of burnout is simply to get rid of the wax in
the pores of the investment to make it porous and strengthen the mold
so that it is more ceramic like than simply hard plaster. As you
pointed out, when the pouring cup is chalky white instead of grey,
all of the wax is gone. We can get to about 1350 F as fast as
possible if the oven is already at that temperature instead of
starting out at room temperature or 300 F as often suggested. The
free water in the pores of the investment will keep the mold
temperature from rising above 212 F (the boiling point) until all of
the water has turned to steam. Then the temperature rises rapidly to
almost the oven temperature to complete the burnout. I have placed a
thermocouple in the center of a 2 x 2-1/2 inch flask and showed that
the core temperature stayed at 212 F for about 20 minutes and then
the temperature rose to almost 1350 F in about another 40 minutes.
I generally use relatively small flasks for my work but I have had
commercial casters tell me of “pushing” their burnout cycle in an
emergency. All that is necessary is that the core temperature reach
around 1350 F and that will depend on the size of the flask.
Successful burnout is indicated by the chalky-white pouring cup as
you pointed out. I don’t know whether there is any minimum time that
the flask should be held at maximum (core) temperature but I suspect
that it is long enough when all of the grey has disapeared. Does
anyone reading this have any technical data on how long the flask
core should be at maximum temperature? I am not referring the holding
time for the oven since the core temperature obviously lags behing
the oven temperature.
I will be interested in hearing any other experiences concerning
fast burnout. Hope this contributes to the discussion.
Before you submerge your flask, B sure 2 let it cool. This length of
time depends upon the metal cast.B SURE that U wear a good
respirator during the quenching process. Micro particles of
investement are dispersed into the air, that are harmful 2 breathe.
In yoga, as in Life, it’s all about your breathe…
there was no temp specified so I took a guess and used water that was
I would say tepid - a bit more than room temp but not hot. The
directions said to submerged and vacuum until all the bubbling stopped
but after nearly 2 minutes it was still bubbling though not nearly as
much as it was at first so I deicided to leave it at that. The flask
was sprue side down.
Does anyone reading this have any technical data on how long the
flask core should be at maximum temperature? I am not referring the
holding time for the oven since the core temperature obviously lags
behing the oven temperature.
I doubt you can come up with any real hard and fixed times here. It
will vary according to how much carbon needs to be oxidized in the
investment (how much wax was in the flask, and how much of it soaked
into the investment instead of melting and flowing out). And it will
then vary according to both the size of the flask and thickness of
investment through which oxygen must travel to do that job, and
finally, and perhaps even harder to quantify, the amount of oxygen
available to the investment, which will depend on the amount of
ventillation in the oven, as well as air flow patterns. Even the way
the flasks are placed and supported will affect this. It’s important
since if you’re burning out without oxygen, the carbon won’t burn
away at all. One reason some casters find differences in performance
between electric and gas fired burn out ovens is precisely this, that
the gas fired furnaces have greater rates of ventillation, even
though much of the oxygen in the furnace is being burned by the fuel
gas. And it’s also one of the reasons why some small furnaces,
enamelling and PMC types especially, may not be suited to casting
burnout, if they lack sufficient ventillation to allow an adequate
inflow of oxygen and gas circulation to carry that oxygen to the
investment.
With all that said, of course, one certainly can come up with times
required for typical burnouts in most situations. For small flasks,
usually a hold time of around an hour is sufficient. Given that this
is with the usual slow burnout, it probably is is close to the time
the flask core is at these temps too. Larger flasks with more waxes,
need more. Steam dewaxing reduces the times needed.
Trial and error may be the best way. Easy enough for a caster to
keep notes and find the best times for their own burnout method.
Great little book you’ve got there, by the way… Well done indeed.