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Vacuum or Pressure

T

Tephy

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Pressure ...

When using vacuum the resin will froth as the air is drawn out and if the resin starts to set while this is happening then you will have wasted the pine cones and resin.

Carefully mix so you don't generate lots of air bubbles ( you can warm it and the air bubbles will rise ) .. slowly pour into mold with cones in .. I normally swill it about to remove trapped air in the cones if you know what I mean, I know someone who dips the cones to make sure they are coated before pouring the resin...... top up resin and then in to the pressure pot.... not had a problem so far :ciggrin: :pray: :whistling:

Have a play experimenting is half the fun ... :devil:

This should explain it better : https://www.youtube.com/watch?v=7IX9RvH5rxI
 
TK woodman

TK woodman

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I have only ever used vac ( but i dont do that much casting ) I can't really get the concept of what added pressure can do that atmospheric pressure will not dowhen the vac is released The only thing i do is vibrate the casting while under vacuum
 
paulm

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Vacuuming is used to suck resin into voids and pressure to remove bubbles or at least make them so small you can't see them. If you want to stabilise wood you would vacuum it with resin such as cactus juice to get into all the little holes in wood. When casting, you would use pressure. So if you want to use a punky piece of wood in a cast, first I would stabilise it with resin in the vacuum chamber and then cast it and put it in the pressure pot.

Confused... so was I till I started doing it.

With pine cones, I have stabilised them first but the shiny outside of them is pretty impervious and doesn't allow a lot of resin to penetrate into it so it is just as well to cast it staight with pressure.
 
TK woodman

TK woodman

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Ok - I thought it was the other way round - Vac sucks - Pressure pushes probably why i dont cast often
 
Buckeye

Buckeye

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TK woodman said:
Ok - I thought it was the other way round - Vac sucks - Pressure pushes probably why i dont cast often
Click to expand...

You are right, vacuum sucks the air out of the wood or pine cones and when you have sucked all the air out of the wood or cones and release the vacuum the cones suck the resin in to replace the air you sucked out, well that is the theory, but casting resin is usually to thick to get into small pores in cones or wood and if you are not careful the resin will be setting up before you have reached anywhere near full vacuum. Some people start with vacuum and release it then use pressure.

Pressure will push resin into voids and reduce bubbles, but you may still end up with small voids or bubbles, but not enough to worry about.

Peter
 
Jim

Jim

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Definitely pressure Mark .. All done at a steady pace .. :bwink: Imagine saying that to an Ossie .. :ciggrin:
 
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