need some help

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DB in VT

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Oct 13, 2016
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115
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Vermont
I have started casting my own blanks. I purchased some Alumilite clear. So far I have cast about a dozen blanks. My pressure pot is setup to run at 40 psi and I leave it running for about 75 minutes. Then I release the pressure and let the cast sit overnight.
The work is being done in my basement workshop where the temperature is around 60 degrees. I bring the mold upstairs to room temperature for the overnight time.
Here's the problem: Bubbles. Sometimes lots of bubbles; sometimes only a few. I'm also have difficulty getting the resin into all the void areas when casting with wood.
Is the temperature I'm working at too cold? Why do so many bubbles show up when the pressure is at 40 psi?
Any thoughts and comments will be appreciated.
 
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McKenzie Penworks

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Mar 11, 2012
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Waxhaw, NC
40psi should be plenty to avoid bubbles.. Assuming the resin isn't already too far cured by the time you get it into the pot. Are you getting these even if you have just straight alumilite?
 

Kenny Durrant

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Sep 11, 2012
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Sachse Tx. 75048
My thought is that it could be air or moisture. As mentioned before are you warming the mold and resin? My process is that I'll take the mold with the tube or other materials that I'm wanting to cast and put them in the oven anywhere from 15 min to 45 min. I'll also warm the resin. Not to get it hot but to help it flow. When I feel comfortable that the mold and it's contents are warm and moisture free I'll mix the resin with the hardener and pour quickly in the mold. I've found trying to play with or fish out the bubbles just wastes time. It's better to let the pressure pot take care of that. I let Alumilite stay under pressure for at least 2 hours. If you release the pressure too soon and the resins still soft the bubbles will expand causing failure.
 

ramaroodle

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Feb 15, 2018
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Location
Seattle
My thought is that it could be air or moisture. As mentioned before are you warming the mold and resin? My process is that I'll take the mold with the tube or other materials that I'm wanting to cast and put them in the oven anywhere from 15 min to 45 min. I'll also warm the resin. Not to get it hot but to help it flow. When I feel comfortable that the mold and it's contents are warm and moisture free I'll mix the resin with the hardener and pour quickly in the mold. I've found trying to play with or fish out the bubbles just wastes time. It's better to let the pressure pot take care of that. I let Alumilite stay under pressure for at least 2 hours. If you release the pressure too soon and the resins still soft the bubbles will expand causing failure.
Going through the forums before I start casting....
How do you "warm" the mold and resin? What do you put the resin in to warm it? Do you put the bottle in hot water? How hot is the oven when you warm the mold? Mine are HDPE molds.

Why not keep the pot pressurized overnight while it cures?

I've read that I should wait until the alumilite stars to thicken before adding accent swirls etc?
 

JohnU

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Jan 31, 2008
Messages
3,881
Location
Ottawa, Illinois
I place my molds in the tank and place a clamp light over it. I also put my cups of resin under a light for about 20 minutes. You’ll know if it’s thin when you stir it. Just don’t get it too hot or it will cure too quickly. Leave the pressure in the tank. Releasing it before the resin cures will only allow the air to be visible.
 

ramaroodle

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Feb 15, 2018
Messages
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Location
Seattle
I place my molds in the tank and place a clamp light over it. I also put my cups of resin under a light for about 20 minutes. You’ll know if it’s thin when you stir it. Just don’t get it too hot or it will cure too quickly. Leave the pressure in the tank. Releasing it before the resin cures will only allow the air to be visible.
Excellent! Thanks.
 
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