freeze dried

[old3dogg]

Thanks Brian.
It all sounds interesting but it would be a slow process in drying wood.There is a lot of water in wood.
Mike.

[Brian_Bailey]

Last fall I sawed out some 12 & 16/4 x RW butternut for carving.
I stickered them O/S under cover.
I live in WNY so since Dec. the outdoors temps. have been alternating between a freezer and a refridgerator.

This AM I pulled a cant out of the stack and cut it in half.
This is what I found after a good 6 mos of air drying.
The shell tested 14%mc and the core was 34% or at least that is what my meter said.
Just looking at the core shows it to wet for carving..



I'm not trying to be confrontational, I just don't see how putting a chunk of wood in the freezer for a couple of days and then in the fridge for a week will give you dry wood.
If it can be done, I would certainly like to know the method   .

[Den Socling]

Brian,

It can be done with a very strong vacuum. The atmosphere over your head is putting the pressure equivalent to a 760 mm column of mercury on your body. What was it that I said this morning? 4.6 Torr? That means that you remove all of the pressure except for 4.6 mm. If we did that to you, you would be a messy cloud drifting off into the sunset.  

Den

[Buzz-sawyer]

Old3dogg
We used a small4-6inch glass dome, on a rubbere matt seal.....using a small, loud, annoying vac. pump...

[Brian_Bailey]

Den,  

I've long been accused of being the source of smelly clouds drifting along. I've always denied any involvement, but me thinks that it's a fermentation /pressure release process .

But seriously,  I have a good market for carving wood and lately there has been a lot of interest for turning wood that is dry enough that it won't crack and distort before you can get it off the lathe.
If I can substantially cut the long wait between wet wood and dry, maybe my business could turn a profit   .

When someone posts a method for quick drying, I'm very interested in hearing about their method.

But on the other hand, I'm not interested in spending dollars to save nickles  .

[old3dogg]

So do we pull a vacuum,freeze the wood,let it thaw,freeze the wood,let it thaw,etc,etc....?
Im only asking because I dont know.

[etat]

Things I thought I knew.  Water turns to steam if you get it hot enough.  Water turns to ice if you get it cold enough.  When it's steam it goes into the air.  When it freezes it gets cold, expands, and turns hard.  Get enough water in the atmosphere it turns to rain. Mix hot, and cold, and atmospheric conditions just right it might turn into a storm. Green wood has water locked inside.  Getting it out is tricky without busting the wood. I didn't know this was a complicated question when I asked it, but I still can't get it in my head how freezing wood will help get the water out, unless it includes a vacumn as stated.  I did not know that water could be frozen and boiled at the same time. I do find that very interesting.

[Brian_Bailey]

Here is how I see it.  

The water freezes and becomes a solid (ice).

When the conditions are right, the ice (frozen water) sublimes to a gas (water vapor) and then evaporates into the atmosphere.

Hence, where the water once was, it is no longer and now dry   .

When the water leaves the wood it leaves as a gas, not as a solid or liquid.
So, there shouldn't be any damage to the wood.

The question is, is it practicle to dry wood using this method?

[Den Socling]

I think there is something else. When there isn't much water left and it's trapped in places where there are few ways out, you normally raise the temperature to increase the kinetic energy of the molecules to improve their chance of bouncing out. At 32'F, their butts are probably dragging.  

[Brian_Bailey]

Den,  

The water is now a gas.
Wouldn't it diffuse out of the wood quite readily without any additional heat as long as the sublimation conditions were maintained?

[Den Socling]

Brian,

This is getting as bad as some of the discussions between Wim and me at the PCS forum!   He's the physicist who's always spoutin' gas laws (unlike most of us who only spout gas  ) but I would guess that temperature adds energy to gas molecules as well as liquid and solid. In fact, that's why warm air rises.

Did you know that warm, moist air rises in a vacuum chamber. This is one that the physicist have explained differently. The water vapor is suppose to spread evenly.

but,   I'm no 'perfessor'.

Den

[Brian_Bailey]

Thanks for the info Den  .

I'm no physicist either  .

I'm just trying to get my hands on a simple / effective drying system for those thick chucks of wood I have.

Your vac. system seems to be the way I'll eventually head. But for now, its design is a little to complex for my abilities.
I eagerly await the results of others  .

I have spent quite a bit of time the past couple of days reading about this freeze dry stuff.

One thing that became apparent was the lack of info on drying wood with this method.

As a lay person this indicates to me that this isn't a viable drying method to persue.

So for now I'll just have to let father time just click along  .

I was wondering if it would be possible to magnetize the water in the wood some how. Then just place a large magnet at the end of the boards and pull all the water out ?  

[Den Socling]

Actually, the magnetic property of water is what enables RF kilns and microwave ovens. But instead of sucking it out with a magnetic field, you swing the molecules back and forth fast enough to heat them with friction.

[jimF]

In all drying, no matter at what temperature, what is happening is that the vapore in the air is applying a pressure on the water in the wood.  If the "vaspor pressure" of the water in the wood is greater than the vapor pressure in the air the water in the wood overcomes the air vapor pressure and escapes into the air.  By adding heat you give the water in the wood enough energy to overcome the air vapor pressure.  In vacuum/freeze drying instead of giveing the water in the wood more energy you are reducing the vapor pressure in the air so the water in the wood does not have such a large  vapor pressure to overcome and is able to escape in the air.

[Brian_Bailey]

The theory behind all these different drying methods is certainly easy to grasp  .

Now all we have to do is make the mechanical apparatus to accomplish this easy to grasp for a guy like me with limitied funds .

I'll wager good money that there would be a strong market for a small 100 / 200 bf vac kiln designed just to dry thick chucks of wood for carving / turning.