Moisture Absorbers for Protecting Wood?

      In an unsealed space, a moisture absorber won't help keep wood dry. December 11, 2007

Question
Does anyone have experience with calcium chloride moisture absorbers such as Damp-Rid? We are having a lot of rain and I want to protect my wood supply in the 50F warehouse so that I can still do some production during the rainy season. It says that it maintains a RH of 60%, which equals 11% E.M.C. Will this give me some flex space for end-glued up panel tops 24x48 made from 3/4 4" thick cherry/walnut/maple boards? It's better than nothing, but I just don't want the stuff I made in winter to buckle in the summer. San Francisco summers are about 70F - 70% R.H.

Forum Responses
(Furniture Making Forum)
From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
Is the warehouse sealed? If not, then it will not work. The wood is actually a better absorber than the chemical. To change the MC of 1000 BF of lumber requires about four gallons of water. So, figure out how much water you need to absorb, and you can see that the chemical cannot absorb enough unless you have a huge pile of it. Once the moisture is absorbed, what will you do with the chemical? What if more water comes into the building after the salt is saturated?



From the original questioner:
Thanks Gene. The warehouse isn't sealed. The dust collection system is constantly pulling air out one end of the building. As a result, fresh air is being sucked in the big receiving doors. We took measures like caulking cracks and installing weather stripping, but it does no good when those big tractor trailers offload daily shipments and those huge rollup doors are wide open in the rain. My hygrometer said 80% RH outside the doors and 75% near the wood storage racks. Not a good thing. We're thinking about sealing the warehouse area with plastic sheeting and installing electric de-humidifiers. You think that will be sufficient? Production time from rough mill to finishing is only two days. That includes picking and pulling material. Once in finishing, the product is safe because we have positive pressure, environmental controls, and monitoring in that closed off area.


From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
The plastic idea is great. I would be concerned about the accuracy of your RH measurements, as 75% RH is quite high and unusual.

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