The Cootie Kiln

I’m in my shop and things are humming along, I need to grab a special board out of my stored stash of special boards when, BAM!

COOTIES!

Yes, these dust filled channels in my sacred boards are made by a particular wood destroying cootie, called, Lyctoxylon dentatum, or more commonly, the Powderpost beetle. There are several beetles that destroy wood, but this one, also referred to as Lyctinae, is identified by its creation of very fine flour-like wood powder, called frass.

My Sacred Boards

I brought these boards to Ohio from my former residence in California. They are very unusual, and I am not sure of the species. It was described as Pepperwood, a local name for Umbelularia Californica (also know as California Bay Laurel, or Myrtle in the world of luthierie), but I have had lots of Bay Laurel and it never looked remotely like this. I have a total of seven boards, all sequentially sawn from the same bole. This wood is not replaceable.

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I have had Powderpost beetles before and thought I had ended the infestation by cutting and removing the infested areas of those boards. I tried a borate treatment first and that didn’t work. I didn’t want to trim these boards because I wanted the live edge, so I needed a different solution, and that solution was …

The Kiln

I found several articles written by etymologists on the life cycle of Lyctinae, and those articles addressed the mitigation problem as well. Of the several strategies to rid wood of these pests, only one was sufficient to kill all three phases of the beetles life stages, egg, larva, and adult, and that solution was heat. 133 degrees Fahrenheit, to be specific; so I sought a way to cook my wood and with it any eggs, larvae, or adult beetles. I needed a kiln.

If it were summertime, I could have simply placed my wood out on the driveway covered in clear plastic. But it wasn’t summertime, it was wintertime, in NorthEast Ohio. It’s cold here in the winter and it isn’t very sunny, but the internet is a wonderful thing. I found a brief description of someone building a kiln using halogen lights as a heat source and styrofoam as an insulating cover, so I set about that.

Planning

I bought two 4×8 sheets of 1 1/4″ styrofoam insulation and three 500W halogen lights. I also bought an inexpensive temperature controller and a bluetooth thermometer that I could monitor on my iPhone.

I mounted the three lights on a couple of 2x4s and slid them under the top beam of the sawhorses. Then I hooked a controller up to two of the lights.

I only hooked up two lights. I didn’t want wild temperature swings, so turning off only two would cause a gradual temperature rise and fall. My “off” limit was set to 145 F and my “on” setting was 135 F, so I always stayed above the 133 minimum.

I built a box with only five sides. The bottom was open.

And thermometers, man, did I have thermometers! This kiln was instrumented with 8 thermometers placed all about the inside, so I knew where the hot and cold spots were. Three were long spike thermometers, one for meat, another for candy, and a third for compost. Those I pierced through the styrofoam. Two were cigar humidor thermometers (The Caliber II, a great device that can be calibrated) that I reached under and place on the sawhorse beam. And the last two were bluetooth that I could read remotely. They also sat on the sawhorse beam.

Preparing the Wood

Changing temperature in wood changes the moisture content. Rapid changes can cause cracks and other deformations as the wood moves. I clamped the wood, using spacers (stickers) and clamped it together with threaded rods.

Not Too Hot

Although I covered up the bottom of the open kiln with cardboard pieces, it would not get hot enough. Barely 130 degrees at some points, so I added a fourth light and also a skirt of rosin paper.

After placing the cardboard back, this arrangement really did the trick. Easy to get over 150 degrees. Two lights were always on, two lights were controlled. This worked great!

Now, to cook for seven hours.

More Wood

I had three more batches to put through. That included Honduran Mahogany, Claro Walnut, Bay Laurel, Spalted Maple, Hawaiian Koa, and more “Pepperwood”.

This included some very nice Bay Laurel (below) that I will eventually cut into veneers.

Afterthought

I should have known better. I read enough while researching this to know that I should raise my temperature slowly. On the last batch I circled cracks with chalk, such that all of the crack was inside the chalk line. When I removed the boards after treatment I could see that they had cracked more.

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Next time I will ramp up to 140 degrees slowly. There are charts that lumber driers use to safely raise temperature in their giant kilns.

Going Forward

This whole process cost me over a week of time, but it was worth it. I have the rig if I need it again and I saved some irreplaceable boards that are in my future project plans.

This episode taught me to be more vigilant. Now I climb the ladder and visually inspect every couple of weeks. I also have a spray bottle with Tim-bor borate solution that I spray around the wood stacks. I’m also a little more aggressive toward bugs. If I don’t know what they are they have to die.

But spiders are still ok.