Vacuum Chamber to help reduce seasoning time

[OtisT]

My old vacuum chamber was a PITA to work with so I turned a boiler into my new vacuum chamber.

Vacuum chamber

The old vacuum chamber was a blue plastic barrel that would collapse under too much vacuum, even with some internal braces I had made for it. This meant I had to soak a lot longer under a lighter pressure than desired. The new keg boiler vacuum chamber has no problem handling the increased and sustained vacuum pressure I want.

I’m using vacuum to soak wood when it is completely dry, to help reduce seasoning time. Once my wood dries down to 2% or 3% moisture there is not much additional “seasoning” going on. Normally, the wood would just sit dry for months until fall. With our dryer than shit summer I was able to lightly soak and completely dry wood several times this summer, which has done wonders for reducing tannin levels in my Oak.

I can get about 50# of wood in my keg per soak cycle, which fills the barrel about 2/3 full. I add water to cover the wood, leaving about 4 gallons of air space which is necessary for in the vacuum chamber. I have been soaking each batch for about 24 hours under -15 to -20 inches of mercury, which has been increasing the wood’s moisture level by about 3% and adding about +4 lb total weight per batch. I just recently began recording weight and moisture levels before/after a soak. I’ll keep doing so until I learn what targets I should be shooting for.

Here is my latest seasoning project, about 80 board feet of American white oak staves.

Am Oak staves stacked for seasoning

It will likely require 5 batches to process this new stack.

Otis

[fizzix]

Help me, Otis. I'm still new and dumb and don't quite understand.

I can see the vacuum sucking out any lingering saps and such in a dry environment, but you say you're soaking it during the process.
How does soaking under a vacuum season it?
Use small words and puppets, please.

[OtisT]

Sorry Fizzix. I did just jump right to done, didn’t I? I was treating this more like a “what did you make today” kind of post because I was happy my new vacuum head on my boiler worked so well. I did not think someone would want to know what I do with it. Doh!

So, I will step back a bit and explain what i am doing.

I am seasoning several species of oak.

My understanding of outdoor seasoning is that the wood is “washed” with each deep wetting and drying cycle. (Washing is one aspect of seasoning) This wash process is what removes a lot of the tannins from the wood during seasoning.

My summers have been very dry, and wood dries out relatively quickly outside. Once stacked wood dries out in early summer the wood remains dry for months and months until late fall when we start seeing rain again.

By vacuum soaking the wood each time it dries out, I can get several “seasons” in over the course of a summer.

I tested this out with a small quantity of oak sticks earlier this summer. I soaked the sticks then let them dry outside. I repeated the cycle twice more. I made teas using my test wood vs some that was set aside as a control, and the difference in bitterness and astrigency was very noticeable with little to no difference in color. I figured I would apply the same treatment to some new oak I picked up recently and hopefully get through a dry cycle before the rains hit.

My first large scale chamber was rigid plastic and did not handle the amount of vacuum I needed to apply before it would collapse. Then I thought about how I pressure test my boilers when I make a new one, and figured it would handle vacuum just as well. The boiler is not as big, but I can get a lot higher vacuum.

Hope this makes sense now.

Otis

[fizzix]

Ahhhh, very well explained and makes complete sense now.
Nice stack of wood ---best of luck to you!