Pressure and Vac??/

[jttheclockman]

For those that use both pressure and vac for their casting. What are the readings for both Vac and for pressure??? How long do you leave each way???? I have my pot up and ready to go finally.

 

[Blind_Squirrel]

It depends on what I am casting. If I am just doing solid PR I crank the pressure up to 60 PSI. If I am casting to a tube I go with 18-20 PSI. When casting I always leave my PR in the pot for a minimum of 12 hours. I cast using 3 or 4 drops of mekp/oz.

I have stopped using vacuum for casting. I use an ultrasonic cleaner to help remove air before casting. I do use vacuum for penetrating wood (i.e. stabilizing). Take the vacuum as high as you can get it. I leave it in the pot a minimum of 12 hours.

 

[NewLondon88]

For those that use both pressure and vac for their casting. What are the readings for both Vac and for pressure??? How long do you leave each way???? I have my pot up and ready to go finally.

Pretty much what Scott said .. around 20 PSI for casting (I haven't really
done any worthless wood or stabilizing to speak of) and I put it on the
radiator overnight. It probably gets up to 100 or so.. not hot, not cool.
The radiator shuts off at midnight and turns back on around 8AM. It might
be there around 14-15 hours or so. Next day by my watch, I'm not that
picky about it.

Vacuum .. let it run till it stops pulling out air.. probably 25-27 or so.
I use that for the wood hardener and the silicone. I do it for several
minutes, long enough for the silicone to rise and fall. The wood hardener ..
the vacuum doesn't get the hardener into the wood, releasing the vacuum
does. You want the vacuum to get rid of the air. When you release the
vacuum, the wood draws in whatever is touching it.. be it air, resin or
hardener. I vac and release several times, but not for all that long.
In fact I let it rest longer than I leave it under vacuum. But you've got to
get the wood under the liquid. It's easier to draw in air than liquid, so it
part of the wood is above the fluid line, it will only draw in the air.

At least that's how it works in my brain ..

 

[MesquiteMan]

If you are using Alumilite, don't try doing vacuum and then pressure. There is just not enough time for both. I only cast embeded stuff and I use 80-100 psi. Do I really need that high, probably not but I have the equipement to do it and the higher, the less bubbles. I get about 99% bubble free in complex embeded objects such as cactus skeleton. WIth Alumilite, I leave it under pressure for 15 minutes and then take it out and let it cool down. When cool (about 20 minutes) I demold and cut them into blanks.