Drying wood in food dehydrator

L

lel

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Dec 26, 2006
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I want to share my experience using I food dehydrator for drying wood and ask for your recommendations and suggestions.
I recently bought a very nice piece of figured redwood that I wanted to cut into blocks and send for stabilization. The wood board was described by seller as dry, it also looks dry, and feels very light. I do not have any equipment to measure the moisture content though. After cutting a few blocks of that board and decided to put them to food dehydrator for a few hours. I also put there 4 pairs of various wood scales which were also bought dry and were sitting in my garage for over a year in a box with a few silica gel bags. I weighted the redwood block and the scales before drying. Blocks were 21.7oz and the scales were 14.3 oz. Then I set the temperature to 140F. After 4 hours I decided to check how things are going. Unfortunately I found that one of my blocks has 2 cracks. I inspected the scales and found a very thin hairline crack on one of them. I am not sure if the crack on the scale is new (I could have overlooked it before) but the blocks were all perfect and solid before. The blocks lost 0.7 oz and the scales lost 0.3 oz, which is 3.2% and 2.1% of their initial weight.

Now the questions - a lot of them. What did I do wrong? Was my temperature too hight? Should I had to wait for a few days or weeks after cutting the blocks? Is there a way to find out whether the wood is dry enough for stabilization without using any expensive equipment? What should I do next - keep air drying that wood of put it back to dehydrator. Will anchor seal coat help me here?

--
Sergiy
 
Should have cut the blocks and other stuff from garage and stuck them. "Stick" is the term. And I suppose you know that already or maybe not. You cut the slabs and put sticks "flat 3/4 inch or one inch slats. Put them in-between the boards and do nothing for a long time. Six months or more. Never speed dry any wood you have just cut. I cannot stress this enough. I know this from my home building years. You put the slabs with grain going up on one layer and grain going oposite in the other layer "going down". Actually anual rings, not grain. Then if possible place said material in the place you will be working later even though it will already be stabalized in-between this. In other words stack them in your work shop unless we are talking tons. Your wood you bought "as dry" was more than likely stored in the same condition or close. After that do nothing but send them out for stabilizing. Personaly if it were me doing it I would first cut them to the slab thinkness desired allowing for future planeing of course. I would have wet the boards after cutting, then stick them. Then I would let them dry on their own. Nothing rapid. And making sure that when you stick them you did it in layers with the anual rings going oposite for each layer. When you cut lumber no matter how dry you are still exposing the interior to air. And no matter how dry wood is "with some extreem exceptions of course" the inside "dead wood" will still have a moisture content greater than the outer layer "sap wood".

What do I base this knowledge on. Years of experience in the homebuilding trade. And oh yes. Airconditioning is made not only to cool but to remove moisture in the air--as you know. It would have been better if you just laid the wood you cut in the AC being stuck, rather than sticking them in a dryer and trying to speed dry them. But the most desireable method is the one I described. If you rip a board along the grain "ie" rip a 2 x 6 in half leaving roughly 11/16th inch thick boards X 5.5 inch wide. 3/4 inch minus saw blade thickness anyway what ever that leaves. Lay those boards down or stack them without sticking them and see what you get. A bunch of cupped lumber.

Now that is what I would do. Their maybe "not maybe" there will be someone out their that has a more technical experience with this. What I said is based on my knowledge of lumber and on how it acts in a real world working enviornment.

Hope this helps. I would still store "stick them" them, even after haveing them stabalized, in the work enviornment where you will be re-cutting them later. Always letting air flow between is the point and keeping layers in alternating anual rings "up then down etc etc" in each stack. You may not be talking that much wood but I think this gives you an idea of "what I would do". I think anyone would tell you to keep the heat away from freshly cut lumber. Slow is good, fast is bad in drying wood, for the purposes in your application of course. and the other question what to do or how to determin. You will want to call the company who will be stabilizing your wood and get their input. If you stuck the wood in a garage there will more than likely be some other type of drying to be done. But keep that wood away from that food dehydrator. It would be much better if the wood spent two seasons after cutting to desired sizes in the house with air conditioning in the summer then heat in the winter. Then ask what to do next from the company doing the stabalization.

Now if you are talking real small pieces proceed as much as you can with the process I described.

As I said someone with more technical expertise will chime in, but this is my experience in real world working conditions.

The cracking and hairline cracks you described were caused by, rapid release of moisture and by that, rapidly shrinking the wood and ooops all kinds of cracks.

Cheers,

Daniel
 
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140°? Heck, I just made 11# of beef jerky and I never go above 135° on it. If you really want try to speed dry it, try using your freezer. A self defrosting freezer will dry it much slower than the dehydrator and no heat warpage would occur. Not sure how well it would work, but it's worth a try.
 
Thanks, guys. I think I will just let my wood sit for a while and see if it gains or looses the moisture and then will send it for stabilization. I searched for "moisture meter" and was surprised that they are cheaper then I thought - a lot of them in $15-$35 range. I am not sure how accurate they are. Have anyone used a meter similar to this one? The first review on this unit tells me it might be a piece of junk.
 
As with hair cuts, sex, paint jobs,..........and drying wood.........
anything you try to rush many times faster than it is meant to happen will not usually turn out well.

100F is about as high as you want to rapid dry wood, and even that cab cause cracking.
 
Stacy, I will remember to go below 100F if I ever want to try that again. I usually set the dehydrator to 110F when I dry mushrooms and to 135F for apples, so I thought 140F should be fine for wood. Now I see how wrong I was. As I mentioned the wood was initially dry so I just tried to remove a few more percents of moisture and make it as dry as I can. Do you guys just send the wood that was in your shop for a few years and is in "equilibrium with its surroundings" for stabilization and do not worry about getting the moisture content below 10%?
 
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