Whenever I kiln dry reclaimed lumber the ends of the boards tend to crack and/or check. I need to find a way to minimize or eliminate this. I need the boards to dry more uniformly. I thought about putting end sealer on the ends of the boards before I put them into the kiln but I don't know if this is a good idea or not. Does anyone have any suggestions?
Needing suggestions on kiln drying reclaimed lumber
- Thread starter Reese E.
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Cliffhanger9
ArboristSite Member
Definitely interested to learn more about drying myself as well as I was having the same problem - but with logs that had been sitting out for a year or two and then milled, just air drying within 20 hours of milling was getting 3-4+" deep checks (pretty short little logs and about 1" thin boards and just sorta playing around with them so not a huge loss). One thing I've heard is to put your stickers as close to the ends as possible, that the checks wouldn't go deeper then them - not much experience to share on the validity of that yet (until I get my 064 rebuilt and mill put together) so interested to hear what others say..
brookpederson
Prairie Lumberjack
Can you control the speed of your drying. I only air dry, but I do know that if you dry any kind of wood to fast it going to crack.
VA-Sawyer
Addicted to ArboristSite
What do you mean by reclaimed wood? Normally that refers to lumber that is re-cycled from existing older buildings. Such wood tends to be well air dried and should not have cracking problems when dried from nominal the 10-12% MC of well air dried, down to 6-8%MC in the kiln.
If the wood is exposed to rain or other moisture, then things are different. End checking often starts due to sunlight drying the ends of the log so fast that micro checks start in the end grain. They act like short tears in a piece of paper, making a weak zone that will continue to crack under drying stresses. Making a fresh cut with a sharp blade on the end of each board that removes ALL of the checks and then end coating with Anchorseal is the best way to prevent checks from spreading. You may have to sacrifice 4" on each end to prevent checks from spreading 6 or even 8 inches as they dry.
Rick
If the wood is exposed to rain or other moisture, then things are different. End checking often starts due to sunlight drying the ends of the log so fast that micro checks start in the end grain. They act like short tears in a piece of paper, making a weak zone that will continue to crack under drying stresses. Making a fresh cut with a sharp blade on the end of each board that removes ALL of the checks and then end coating with Anchorseal is the best way to prevent checks from spreading. You may have to sacrifice 4" on each end to prevent checks from spreading 6 or even 8 inches as they dry.
Rick
Cody Colston
ArboristSite Member
Lumber end-checks because the ends dry first. The long-grain ends are like a bundle of soda straws which provide the easiest path to evaporation for the moisture inside the lumber.
As lumber dries, the ends shrink across the grain but the rest of the wood doesn't shrink nearly as much because it is still at a higher moisture content. The stress that is introduced literally pulls the wood fibers apart, resulting in the end checks.
Sealing the end-grain with something like Anchorseal will help a lot but staying below the safe drying rate for the specific wood being dried is the most important thing you can do, both for minimizing end-checks as well as warping. Kiln drying allows you to control that rate, unlike air drying. In addition, placing stickers close to the ends of the lumber will usually limit the depth of any checks as they tend not to extend beyond the first sticker.
As lumber dries, the ends shrink across the grain but the rest of the wood doesn't shrink nearly as much because it is still at a higher moisture content. The stress that is introduced literally pulls the wood fibers apart, resulting in the end checks.
Sealing the end-grain with something like Anchorseal will help a lot but staying below the safe drying rate for the specific wood being dried is the most important thing you can do, both for minimizing end-checks as well as warping. Kiln drying allows you to control that rate, unlike air drying. In addition, placing stickers close to the ends of the lumber will usually limit the depth of any checks as they tend not to extend beyond the first sticker.
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