I built a wood drying kiln 4’ x 4’ x 16”. Using a dehumidifier, a box fan, a 250 w heat lamp, with 219 Board feet of green white oak. Cut about 2” thick. Started at 45-50 MC and 72 F got up to 93.5 F and 93.5% RH by end of the third day. Dehumidifier is set to 55% which I was planning on lowering down to 40% as the moisture content lowered. By the morning of day 4 the RH reads 82.5 an hour later 71.4. What’s going on here?
Wood drying Kiln
- Thread starter jdez
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Just be clear - are you drying the oak or did you build the kiln with the oak? If the former, what did you used to build the kiln?
I built the kiln with 2x4 from Home Depot. I am drying the white oak for my dining table. There are three boards of American walnut too
1inch foam insulation, wrapped in plastic
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One possibility, and it's a "hail Mary".. Relative humidity ( RH), is as much temperature related, as it is moisture related. It's like why your house needs a humidifier in the Winter... No matter how you raise the air temperature, the air dries out as it wars up.. "Relative" humidity.
Could it be that raising the temperature is getting the wood to spit out more moisture?
How are you draining the dehumidifier?. Out of the enclosure, and into a bucket stops re-absorption of moisture from the reservoir.
Also, ( and I'm not sure if it makes a difference).), a heat lamp warms stuff by radiant heat.. that is that it doesn't much heat the air, it heats the surface that it's aimed at directly. Your air temp might be 90 F, but what the heat lamp is aimed at may be higher. Maybe try a straight electric heater.
Could it be that raising the temperature is getting the wood to spit out more moisture?
How are you draining the dehumidifier?. Out of the enclosure, and into a bucket stops re-absorption of moisture from the reservoir.
Also, ( and I'm not sure if it makes a difference).), a heat lamp warms stuff by radiant heat.. that is that it doesn't much heat the air, it heats the surface that it's aimed at directly. Your air temp might be 90 F, but what the heat lamp is aimed at may be higher. Maybe try a straight electric heater.
I built a similar insulated "dog house" many years ago, but mine was only about 10' long to accommodate 8' rough boards and a small heater at one end of the doghouse. I also incorporated good airflow from end to end. I don't remember the numbers but chucksta seems mostly correct in his remark regarding relative humidity, " Relative humidity ( RH), is as much temperature related ". I think I held the heat maybe 30-50 degrees above ambient - crudely with a space heater. The dry time was NOT instant - but in 3-4 weeks ( I vaguely recall) the lumber was dry. I was drying 1" lumber. Airflow was more important during the early stages of drying and heat was more important in the later stages of drying. Somewhere I read that over drying the lumber to maybe 10-12 percent moisture content, the adding moisture was better, but I never did this. I simply got the lumber darn close to about 15 percent MC, then allowed it to rest in the open air for a week. I was living in Montana when I did these things, and it's quite dry in Montana.
So, I suppose I am suggesting that you eliminate the dehumidifier and simply raise the heat to get the moisture out of you lumber.
And, you should have some airflow too.
Also, I recommend using your moisture meter on the lumber in your home, then target your drying lumber for that measurement. I think I found that my home furniture moisture content varied up to 5% from summer to winter - depending on exposure to ambient humidity.
Hopefully some of my rambling is helpful.
Sincerely,
Dave
So, I suppose I am suggesting that you eliminate the dehumidifier and simply raise the heat to get the moisture out of you lumber.
And, you should have some airflow too.
Also, I recommend using your moisture meter on the lumber in your home, then target your drying lumber for that measurement. I think I found that my home furniture moisture content varied up to 5% from summer to winter - depending on exposure to ambient humidity.
Hopefully some of my rambling is helpful.
Sincerely,
Dave
It is being pumped but it needs to fill the reservoir before it can be pumped.
" I think I found that my home furniture moisture content varied up to 5% from summer to winter - depending on exposure to ambient humidity."
Yup, and that can have a significant effect on wood, for sure. I have a Stratocaster guitar, and it's never left my house. The house was heated in the Winter, and cooled in the Summer to 23 C (73 F), You would think that that would be a stable environment for wood. Nope, that guitar neck changed with the seasons. Weird. And, of 5 guitars, it's the only one to experience this phenomenon.
Definitely , try and match the MC to the wood's future home.
Yup, and that can have a significant effect on wood, for sure. I have a Stratocaster guitar, and it's never left my house. The house was heated in the Winter, and cooled in the Summer to 23 C (73 F), You would think that that would be a stable environment for wood. Nope, that guitar neck changed with the seasons. Weird. And, of 5 guitars, it's the only one to experience this phenomenon.
Definitely , try and match the MC to the wood's future home.
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