sterilizing AD thick slabs

I have a pile of 8/4 hard maple, 15-20" wide, about 7' long. They've been stickered air drying for about 5 years outdoors with a metal roofing cap on them. I went to check on them recently and was disappointed to see lots of powder post beetle piles. I surfaced one board, and it will have to be designated as "wormy" but it has nice color and is quite solid. My question is if I build an insulated heated box to sterilize them now (shoot for 135 degrees for maybe a couple days to heat to core?), will i likely experience degrade from that? They're at about 15 percent now according to my pinless meter. Would I be just as well waiting till spring? No more damage will occur between then and now, right?
Thanks!

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Originally Posted by al ladd

I have a pile of 8/4 hard maple, 15-20" wide, about 7' long. They've been stickered air drying for about 5 years outdoors with a metal roofing cap on them. I went to check on them recently and was disappointed to see lots of powder post beetle piles. I surfaced one board, and it will have to be designated as "wormy" but it has nice color and is quite solid. My question is if I build an insulated heated box to sterilize them now (shoot for 135 degrees for maybe a couple days to heat to core?), will i likely experience degrade from that? They're at about 15 percent now according to my pinless meter. Would I be just as well waiting till spring? No more damage will occur between then and now, right?
Thanks!

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Hi Al. The moisture content won't change between now and spring, so you'll have to dry it down as part of the sterilization process regardless. But no, there should be no additional damage from now until spring.

I've sterilized several hundred bf of wood using my small electric kiln. It's just a really well insulated box with an oil filled heater and fan, with a temperature controller for the heater and a humidity sensor. The old oil filled heaters do not have a high temperature cutout, and do not have digital controls. That's the type I have. If you have to buy one get one with the rheostat or two or three heat level controls, not digital. You likely will have to bypass the high temperature cutout, too, to get up to 130F.

I raise the temperature no more than 25F/day up to no more than 110F and monitor the RH. I sometimes check weigh samples, too. I dry it until I get to 6 or 7% MC then increase the temperature to 135 F and hold it there for at least 24 hours. I have a thermocouple buried in the middle of one of the weigh samples so I can verify it gets up to 135 and has remained there for at least 3 hours. When I'm satisfied I've met the criteria I lower the temperature no more than 40F/day until I get down to ambient plus 40 degrees.

Never had any problems afterwards, either with bugs or degrade from the process.

John

Thanks John, very useful. I think I'll wait till spring so i can place the box outside or in my screenhouse rather than in the shop (closer to the pile too). Really appreciate your ready and sound advice!

Sterilize? Isn't that what the airport scanners were gonna do? I'm no less .... although certainly less capable...

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Originally Posted by Wes Grass

Sterilize? Isn't that what the airport scanners were gonna do? I'm no less .... although certainly less capable...

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Sterilizing wood is not a joke. If the USA would have required that with import shipping skids, we would still have ash trees.