Casting problem, plaster falls from flask

i am a problem with the casting , can anyone help me to rectify the
issue. I am using the kerr plast 2000, plaster. After blending with
38% - 40 % of water to 100 gms of power. After blending it is
debubblezed, and poured into the flask, then dried natural for 45
minutes. Then kept in the dewaxer, the to burn out furnace starting
with 150 degrees, after the burnout cycyle when the flack is
mover/removed for powering the plaster falls like the flakes from
the flask.

... After blending with > 38% - 40 % of water to 100 gms of power.

The investment to water ration is critical. Use the ratios
recommended by the manufacturer, EXACTLY as written.

Try a longer time before steam dewaxing 1 hr 30 min or 2 hours. Then
make sure the steam dewaxer temperature is a little below 100 C. I
used to have problems with plaster spalling in a large steam dewaxer
till we set the temperature down to about 90 C. There will still be
plenty of water vapor just not quite as hot.

James Binnion
James Binnion Metal Arts

… After blending with 38% - 40 % of water to 100 gms of power.

The investment to water ration is critical. Use the ratios
recommended by the manufacturer, EXACTLY as written. 

38-40% is within the manufacturers ratio for this investment

James Binnion
James Binnion Metal Arts

i am a problem with the casting, can anyone help me to rectify the
issue. I am using the kerr plast 2000, plaster. After blending
with 38% - 40 % of water to 100 gms of power 

Nagesh, I would suspect the problem is either due to using the
De-Waxer or perhaps in the burn out cycle. Find a way to check the
temperature of your oven and make sure it is within the proper range.
We quit de-waxing some years ago due to it causing several different
investment problems. We haven’t had an investment problem since. You
might check to make sure the water-powder ratio is exactly in
proportion as well and make certain the investment is fresh… it
does get old.

Hope this helps. Dan.
DeArmond Tool
dearmondtool.com

We quit de-waxing some years ago due to it causing several
different investment problems. We haven't had an investment problem
since 

When we started doing steam de-waxing we had lots of investment
issues too, bad surface finishes, spalling and cracking were not
uncommon. After a lot of experimenting we found that reducing the
temperature slightly got rid of the problems. I placed a
thermocouple probe in the chamber connected to a temperature
controller and kept the chamber at 190 F. Also making sure to allow
the investment to gain its full green strength 1.5-2hrs after gloss
off. Also not moving or disturbing the flasks for 1 hr after gloss
off proved to reduce investment issues.

Jim

James Binnion
James Binnion Metal Arts

Hey James,

I know it’s been a while since this topic was covered, but i’m having problems with my flasks cracking during burnout. I have a new bigger kiln and fit around 9 flasks in it. The biggest flasks 4x7in, the smallest 2.25x4in.
Mixing per the instructions, letting sit for 2-3hours. I have then been dewaxing my flasks and popping them in a preheated kiln at 150c.
12h burnout as recommended by the manufacturer.
It’s driving me nuts. Should i let the flasks dry again before placing them in the kiln after the dewaxing? Don’t know what else to do?

You’re right, this thread is from over 20 years ago. I’ll be surprised if you’ll get a response from a post so long ago.

I’ve never had good luck with steam dewaxing. Can you do a test with fewer flasks, (1-3 flasks), no steam dewaxing and follow the same recommended burn out and casting sequence?

That would let you know if the problem is steam dewaxing or not.

I suppose the other questions are how much wax are you burning out, what is your casting process (vacuum or centrifugal) and what kind of metal are you casting?

Doing a no-steam dewaxing trial burnout is what I would try first myself.

Keep us posted!

Jeff