David Gilbert
11-03-2020, 1:14 PM
Last week I picked up several green, weeping cherry logs. Yesterday I prepped a piece and cored out three bowls. Each of the bowls was about an inch thick and 7, 10, and 12” in diameter. The issue I had was that there were numerous bug holes and presumably bugs in portions of each bowl. I wanted to kill these bugs so I went to one of my favorite reference forums, Sawmillcreak.org, and found lots of discussion and opinion. For your reference, here is a good starting point:
https://sawmillcreek.org/showthread.php?285043-What-is-the-simplest-way-to-heat-sterilize-wood&highlight=kill+bugs
and it included this reference: https://www.fs.usda.gov/treesearch/pubs/37413.
While skimming through all of this I decided that my plan to kill the bugs was to heat the bowls above 133 degrees Fahrenheit and hold them for about 45 minutes. There were two methods that I didn’t see mentioned in these articles: boiling and using microwaves. I don’t have a pot big enough to boil these, so I chose the microwave. I have previously dried bowls in a microwave with very reasonable results. You just need to go in steps, and not overdo it. I wasn’t interested in drying the wood, but just to kill the bugs. Microwave oven heats the water in the wood and the wood provides some insulation so the cooling isn’t too fast.
My process was as follows. I drilled a small hole in each piece for the temperature probe. I used my wife’s digital thermometer. The starting temperature for each was about 68 degrees. Starting with the smallest blank, I heated it at full power for one-minute steps and measured the temperature after each. Once the temperature was recorded, I put it back in the microwave for the next cycle. After several heating cycles the temperature reached 175 degrees or higher. I then let the piece cool and put it back in the microwave when the temperature came down below 140. This kept the wood an elevated temperature for about 45 minutes. I did this for the remaining pieces but moved up to two-minute cycles with the larger blanks.
I remounted the blanks on my lathe and turned them to final size and shape. I probably overheated the two larger blanks because there were some minor surface cracks on the bowls. As I was blowing out some of the frass I dislodged a cooked caterpillar, so I killed at least one bug. All of the other caterpillars I saw were either the front or back half and should have died before going under my knife (gouge), but I can’t be sure.
My plan was to clean the frass from the bug holes and fill them with black CA. I painted Minwax Antique Oil around the holes before filling with the CA. In spite of the MAO, the black CA still stained the area around the holes. On subsequent bowls I will probably go back to my standard coffee grounds with thin CA to fill the holes. The MAO works very well with the coffee/CA to eliminate the CA stain.
I want to add one warning about using your microwave to heat and dry wood. Be very careful when you are drying your wood in a microwave oven. If you get to a low moisture content, you risk heating it up so much that you can make charcoal on the inside of the wood. When this happens, you will get smoke and perhaps a fire. This smoke this creates is very strong, very unpleasant, and very long lasting. I’ve warned you so if you use your kitchen microwave be very careful.
Cheers,
David
https://sawmillcreek.org/showthread.php?285043-What-is-the-simplest-way-to-heat-sterilize-wood&highlight=kill+bugs
and it included this reference: https://www.fs.usda.gov/treesearch/pubs/37413.
While skimming through all of this I decided that my plan to kill the bugs was to heat the bowls above 133 degrees Fahrenheit and hold them for about 45 minutes. There were two methods that I didn’t see mentioned in these articles: boiling and using microwaves. I don’t have a pot big enough to boil these, so I chose the microwave. I have previously dried bowls in a microwave with very reasonable results. You just need to go in steps, and not overdo it. I wasn’t interested in drying the wood, but just to kill the bugs. Microwave oven heats the water in the wood and the wood provides some insulation so the cooling isn’t too fast.
My process was as follows. I drilled a small hole in each piece for the temperature probe. I used my wife’s digital thermometer. The starting temperature for each was about 68 degrees. Starting with the smallest blank, I heated it at full power for one-minute steps and measured the temperature after each. Once the temperature was recorded, I put it back in the microwave for the next cycle. After several heating cycles the temperature reached 175 degrees or higher. I then let the piece cool and put it back in the microwave when the temperature came down below 140. This kept the wood an elevated temperature for about 45 minutes. I did this for the remaining pieces but moved up to two-minute cycles with the larger blanks.
I remounted the blanks on my lathe and turned them to final size and shape. I probably overheated the two larger blanks because there were some minor surface cracks on the bowls. As I was blowing out some of the frass I dislodged a cooked caterpillar, so I killed at least one bug. All of the other caterpillars I saw were either the front or back half and should have died before going under my knife (gouge), but I can’t be sure.
My plan was to clean the frass from the bug holes and fill them with black CA. I painted Minwax Antique Oil around the holes before filling with the CA. In spite of the MAO, the black CA still stained the area around the holes. On subsequent bowls I will probably go back to my standard coffee grounds with thin CA to fill the holes. The MAO works very well with the coffee/CA to eliminate the CA stain.
I want to add one warning about using your microwave to heat and dry wood. Be very careful when you are drying your wood in a microwave oven. If you get to a low moisture content, you risk heating it up so much that you can make charcoal on the inside of the wood. When this happens, you will get smoke and perhaps a fire. This smoke this creates is very strong, very unpleasant, and very long lasting. I’ve warned you so if you use your kitchen microwave be very careful.
Cheers,
David