Replies

1. 
   user-148830 | Jul 06, 2007 03:12am | #1

   Hi Tom,
   You know I haven't microwaved ash to kill bugs. I believe all it takes is something like 140 degrees for an hour or so. I'll get in touch with a botanist I know and get back to you on this. Gary

1. 
   tomsellars | Jul 06, 2007 10:14pm | #2

   Thank you. 2 minutes on high puffed the wood up, steam escaped. Then the wood shrank past its dimensioned size. 1 1/2 minute seemed better. Steam escaping. No noticeable shrinkage. But I used some known bug free ash in the end. I would be surprised if bugs or eggs would survive either. Let me know if the botanist has any info. Thanks Tom S

1. 
   klarsn | Jul 08, 2007 12:43am | #3

   Tom, I have heard of bowl turners putting their bowls in the microwave before finishing them.  I guess a person could set the intensity to a lower setting and be able to set the time longer to avoid distorting the wood.

   Too bad microwaves are so small.  Seems like a good solution to questionable infestation when using air dried wood.

   I have also heard a spec of 120 degrees at the center of the board, at the middle of the stack, for 8 hours.

   I'm going to be watching what is offered, here.

   Keith

2. 
   user-148830 | Jul 20, 2007 06:30am | #4

   Tom,
   Here's some information from Mark Azevedo, a botanist at Oregon State University. He's also got a sideline cutting up Oregon White Oak and other local species. He's a treasure trove of info and great wood. Witness:

   Yes, you can microwave wood to kill insects, but it is not the most
   practical method. A temperature of 130 F or more in the wood will
   dissociate the proteins in the insects and kill them. The normal
   procedure in the kiln is to raise the temperature at the end of the
   kiln cycle (ie- when the wood is at 6-10% moisture content) to
   130F and to shut off the compressor to stop the drying process.
   This temperature is then maintained for at least 4 hours so that
   the core of each board reaches 130F.

   The microwave has 3 obvious problems in killing insects. 1- The
   size of the microwave chamber is limited. 2- There is no practical
   way to control the temperature of the wood and 3- The microwave
   has a venting system (fan) that pulls moisture out of the wood,
   thus potentially creating drying stresses and/or over drying. With
   these limitations in mind, I would proceed cautiously by running
   some tests on the wood of interest by microwaving equivalent pieces
   of the wood (known to contain live ash borers) for varying short
   burst cycles. Allow the wood to cool and cut open to determine if
   the insects (usually larvae) have been killed. I would then
   microwave the wood of interest for the time necessary to kill the
   larvae plus one extra time interval to be sure. Another approach is to heat the wood in a oven that has a good low temperature control for things like raising yeast breads. This would allow you to treat more wood and the heat would be more uniform.

   Tom,
   In other words, the issues are the size of your wood, what will fit into the microwave, and the amount of degrade you might get from losing too much moisture from this method. You'll definitely kill the bugs, but you might lose the lumber in the process. Start with small drying times and work up. Good luck. Gary

1. 
   tomsellars | Jul 20, 2007 06:53am | #5

   Gary, Thanks for the response and advice. I used clean ash on this project to avoid anyconcern. I have a couple of hundred board feet that won't fit in my microwave, so it's off to the fumigator. Thanks Tom Sellars