Thread: Green wood under a vacuum?

You will pull the air out of it, but not the moisture

Placing wood under a vacuum can remove moisture but I am not sure at what rate. When you place the wood under vacuum you actually lower the boiling point of the "water" in the wood and it will literally boil out at a low temp. I am not sure this would be cost effective in the long run. Here is how I dry blanks and it typically take about 1-2 weeks for them to dry out completly.
1. If it is available there pick up some Denatured Alcohol (DNA)
2. Place the blanks in a container (I use a 5 gallon bucket or smaller plastic 'food' containers depending on how much I have to dry)
3. Cover the blanks w/ DNA and weigh the blank down to keep it from floating. (I use pieces of Corian to weigh it down since it will not absorb the DNA)
4. Soak for 1-2 days
5. Remove the blanks and let them drain for about 5 minutes. You may want to wear gloves because the DNA will suck the moisture out of your hands and leave them cracked and hurting
6. Wrap the blanks in plain news print, NO COLOR as the DNA will bleed it out and stain the wood.
7. Stack them for a few days to slow the DNA evaporation
8. after about 4-5 days (maybe less if its hot) remove the blanks from the paper, restack and allow to finish drying.

You can keep track of the moisture either with a moisture meter or by weight. Good luck

Chris

Thanks guys. The thought occurred to me when talking to a chap installing an airconditioner, and he used a vacuum pump to remove any moisture in the lines prior to charging it with refrigerant.

Oh well, it was just a thought.

I'm still not sure what I'm going to do with this vacuum pump, now that I've built it (just seemed like a good idea at the time ).

The posts on pressure containers are interesting. It occurs to me that an LPG bottle would make a suitable pressure pot. It would need a bit of metalwork - cut in half, weld suitable seals/clamps etc on - but not difficult to do. Thinking.......

Originally Posted by dikman

I'm still not sure what I'm going to do with this vacuum pump, now that I've built it (just seemed like a good idea at the time ).

Reverse mount natural edge bowls.

Getting a bit ahead of my abilities here, methinks .

Originally Posted by dikman

I'm still not sure what I'm going to do with this vacuum pump, now that I've built it (just seemed like a good idea at the time )...

I use mine for stabilising and on the lathe for the vacuum chucks

You could try sealing wood in a stout plastic bag and then dropping the pressure inside the bag. Leave the bag in the sun and the heat should cause the water to boil off because of the lower pressure.

I have given this a go. Put a test piece in the vacuum bag and left it with the pump running(on and off) for a couple of days. Tests with the moisture meter showed virtually no effect. I was quite surprised as I thought the moisture would boil off quickly but nothing happened. My moisture meter was on its last legs so that didn't help give a very accurate measure. Next time I'll use the digital scales and do a more accurate test but meanwhile the vacuum isn't going to put air drying out of business.
Other fun things to do with a vacuum are veneering and vacuum infusing cracked or damaged wood with epoxy.

Thanks Len, I think you've pretty much confirmed that it's a no-go idea.
My original thought actually, when I started this, was to stabilise timber for knife handles (which is sort of in line with your last suggestion). Having read more on the subject in this forum, it appears that a vacuum, in itself, is only part of the equation. 'Twould seem that a combination of vacuum and pressure is the ideal, so with that in mind I'm making another "chamber" from a 3kg gas bottle, but this time it will be able to be both pressurised and vacuumised (not at the same time, of course .