WARNING: Involves premeditated killing of small creatures!
How to rid wood invested with woodworm of the pesky little critters? Treatment with poison is a solution, but is messy and dangerous for humans if not done correctly.
A poisonless method is apparently to heat the infested wood in an oven for 24 hours at 100+ degrees Celsius, but that seems too much trouble and a waste of too much energy.
So I thought what about microwaving the wood? Microwaves excite water molecules so that they heat up to boiling point and maybe beyond. So why not microwave the infested wood. The moisture in the bodies of the woodworms should make them boil and die, while leaving the dry wood undamaged. (I've since found out that this method is indeed used in the wood industry, but I'm still taking some credit for the idea because I came up with it by myself.)
SAFETY WARNING: Wood can IGNITE when microwaved too long! Be very careful!
Step 1: Preparation
Of course the size of your pieces of wood is limited by the size of your microwave oven. In my case I'm still using a small 500 W unit from about 30 years back, but it had to do.
After measuring the inside of the oven, it was clear that 27 cm would be the maximum length I could go. Fortunately I was planning to use my piece of bug ridden oak plank for a project where that size would work nicely. So I cut up the piece of wood in four pieces, and was ready to go.
Step 2: Extermination Time
Because my oven is not very powerful, I put in only two pieces of wood at a time, and let the oven run for about 5 minutes. When I opened the oven door after about two minutes, I heard a satisfying sizzling sound. Either some moisture or indeed insects non grata were being cooked.
After the five minutes was up, the wood was too warm to comfortably hold in my hands, and I presumed anything living inside should by fried by this time. I then repeated the process with the remaining two pieces.
After the pieces of wood had cooled down, I cut off the bits that were too far gone due to the insects' indiscriminate eating habits. Then I put the remaining wood through a thicknesser to clean them up, and was left with the four quite usable pieces in the picture. I've tested some varnish on the piece on the right, and it brings the natural colour out quite well, I think.