An improved method to kill bugs in a turning blank.

[David Gilbert]

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....ight=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

[Brian Tymchak]

Are you still married?

If my wife knew I was trying to kill bugs in our microwave, much less using the thermometer as well, she would probably kill me and bury me under the basement floor.

[John Keeton]

David, Titebond works very well with coffee grounds and doesn’t stain the wood like CA.

[John K Jordan]

...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,...

Some people use an inexpensive turkey fryer to boil bowls and blanks but I can't remember if mine will hold a 12" bowl. Boiling has other advantages such as relieving stresses and softening the lignin so minimize cracking. I have used a microwave to dry small pieces but I like the boiling idea - I think I'll drag out the turkey fryer the next time I get buggy blanks. I think Steven Russell said to boil one hour per inch of thick thickness. He said boiling a longer time doesn't hurt anything so that might be an advantage.

JKJ

[Robert D Evans]

Yea, well, I've been banned from using the Wife's cooking tools in my hobbies. No more powder coating in the oven or microwaving bowls and especially, no washing paint brushes in the kitchen sink.

[Brice Rogers]

I think that I would have put the wood in the oven and set it for something like 140-150 F. Of course I would have to wait until my wife wasn't in the house...

[John Keeton]

I vote for Brice’s approach.

[Richard Coers]

I think that I would have put the wood in the oven and set it for something like 140-150 F. Of course I would have to wait until my wife wasn't in the house...

You have to be careful with that type and amount of heat. Just setting it at 150 F right after coming off the lathe will usually get you some cracks. Heat like that in the oven will quickly dry the surface and set up a stress situation in the wood if the blank wasn't kiln dried. Even a thick kiln dried blank can have a moisture difference on the surface vs the center of the wood. I start my drying at 90 degrees for a period of time to acclimate the wood. Then bump it up in stages.

[Reed Gray]

Well, I am wondering if steaming rather than boiling would work. I had one friend who used to do that with Pacific Madrone, but that was to stabilize it, not for bug killing. I have known people who microwaved bowls and there were still active bugs in them. I would guess that is because the microwave ovens don't heat totally evenly.

robo hippy

[Kyle Iwamoto]

No one uses the freezer?
I guess our tropical bugs can't handle the cold, but I've put blanks in a garbage bag or 2 and froze them overnight. I drop them in when the wife is busy doing something else. Our mango is famous for bug infestations.
I know some of the bugs there can survive the winter.....

[Richard Coers]

No one uses the freezer?
I guess our tropical bugs can't handle the cold, but I've put blanks in a garbage bag or 2 and froze them overnight. I drop them in when the wife is busy doing something else. Our mango is famous for bug infestations.
I know some of the bugs there can survive the winter.....

Cold doesn't effect all bugs, eggs, or larvae. Lots of them burrow in and that is the way they spend the winter. Bring the wood out of the freezer and they think it's spring.

[Don Stephan]

Five minute epoxy tinted with fresco powders in a Mohawk kit works well for me, doesn't penetrate and stain surrounding wood as mdeeply as CA. for worm holes I'll use a paper punch to make a hole in a short piece of masking tape, mask off the hole, and fill.

[Jeffrey J Smith]

I think Steven Russell said to boil one hour per inch of thick thickness. He said boiling a longer time doesn't hurt anything so that might be an advantage.

JKJ

I’m a boiler - no harm in boiling longer. I usually set up the boiling pot when I rough and core blanks. My pot is an aluminum stock pot 26” dia and about 24” tall - found at a scratch and dent section at a restaurant supply house. I get it setup in the morning and let it go all day and into the evening - just chuck in roughed/cored bowls right off the lathe. They wind up in there an average of 4-5 hours. No effect observed from the first to go in to the last. Ill let it go for a couple hours after the last bowl is chucked in while I clean up the shop just to make sure everything got good time. Mostly I use this for madrone and maple, but roughed some tune that a friend gave me with the warning that it tends to crack - no cracks after several months of drying.
Can’t speak of its effect on bugs - they’re typically not a problem, but I’d guess the internal temperature gets well above 150 for an extended time...

[Brice Rogers]

Richard Coers, that is good advice. Thanks.

[Brice Rogers]

Although it would take a bunch of energy, if I had something really special that deserved extraordinary effort, perhaps I'd try to buy a cheap steel drum - - like a 33 gallon or a 55 gallon steel drum and then cut it down by 2/3's or something. I see them for sale (used once) pretty cheap. Much cheaper than trying to buy a 30 gallon kitchen pot.

Some people use an inexpensive turkey fryer to boil bowls and blanks but I can't remember if mine will hold a 12" bowl. Boiling has other advantages such as relieving stresses and softening the lignin so minimize cracking. I have usechd a microwave to dry small pieces but I like the boiling idea - I think I'll drag out the turkey fryer the next time I get buggy blanks. I think Steven Russell said to boil one hour per inch of thick thickness. He said boiling a longer time doesn't hurt anything so that might be an advantage.

JKJ