Pressure or Vacuum

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I once used both and now I use neither. I only clear cast such things as snake skins and computer logo labels. Check out my article on bubble free casting and the thread I started a few months back. It is in the casting forum. The article is in the library.
Do a good turn daily!
Don

BobBurt said:
Just thought I would ask.

What is better when using PR??????

or

When would you use pressure????? When would you use Vacuum?????

Thanks
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Both can minimize bubbles formed when casting. Vacuum (Ultrasonics works even better) is used to get any air or gas out of solution prior to casting. Pressure is used to keep whatever gas is left from degassing in solution while the resin is setting up. Works like a soda bottle. I use ultrasonics for every PR cast and pressure for clear casts.
 
Vacuum is used more with "stabilizing" blanks. Vacuums pull air out of tiny holes and veins; when the vac is released, stabilizing agent rushes in. Pressure then pushes the agent further in.

AS to vac on casting - it seems to me that vac increase the level of bubbles.
 
Vacuum helps remove any moisture, that the resins may absorb from the air, once their containers are opened.

If vacuuming PR don't exceed 27"Hg as styrene will boil out of solution at 28"Hg.
 
BobBurt said:
OK, Great info so far...

When casting Worthless Wood.....Pressure or Vacuum?????

Tks
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Pressure. This will help push the PR into the wood for a better binding. Some say that PR doesn't work great for WW casting because it shrinks as it cures. I use it but some like Alumite more for WW castings.

Definately Pressure though.
 
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