Because I live in a small town, I don’t usually get to choose the wood I build with. I usually have to use what I have on hand, or what the sawmills have extra of. I have a few small sawmills near me, but the nearest “wood store” is more than 50 miles away, and their prices for high-quality exotic species are often out of my reach. Because of these problems, I build a lot with wood that I can get my hands on quickly, like ambrosia maple, red and white oak, poplar, hickory, and sometimes pecan.
It’s always rough-sawn because I buy most of my lumber from local sawmills. Most of the time, the slabs I buy have the live edge and bark still on them. There are a lot of sawmills near where I live that sell lumber to flooring manufacturers. At least one sends a lot of their lumber out of state to different furniture manufacturers. Seconds: These are the parts that these mills can’t sell to their customers for commercial use. This means that I get to choose my stock from them. So, I often have to deal with wood that has been eaten by bugs.
Take ambrosia maple, for example. By nature, this wood has a lot of little holes made by the larvae of the ambrosia beetle. When the ambrosia beetle, which eats the ambrosia fungi, burrows into a ball of sap that has leaked from a damaged part of the tree, like a broken limb from a storm, the beetle makes holes in the tree. There are small pieces of the fungi that get into the tree through the sap that the beetle has drilled into. This allows the fungus to spread through the tree. Afterwards, the beetle lays eggs, and its larvae keep eating the fungus-infected wood until they turn into adult beetles. They then fly off and find a new tree to lay their eggs in.
In the picture above, you can see that the ambrosia fungus streaks and darkens ambrosia maple, which makes the wood look beautiful. Woodturners and woodworkers love it because of this. You can also see the small holes made by the beetle’s larvae. For most projects, these holes are fine to leave alone. They don’t pose any real problems, except that sometimes they contain frass that might float out of the hole when the finish is put on. As a result, for people who make things that will be used near food, these holes are a good place to start.
Take, for example, some serving trays that I made a while back. The small holes in anything that might come into contact with food are a big problem, because the holes can hold tiny bits of food and food juices that could later go bad and help the growth of bad bacteria. In the past, stock with small holes like these was not used when making these kinds of things. Either wood glue or epoxy and sawdust were used to fill in the holes. People might have to wait for wood glue or epoxy to dry for a long time before they can apply a finish without outgassing. This is not ideal.
The glue in these small holes isn’t going to dry in time for anyone trying to run a production shop or even a small art-market shop like mine. Nobody has time to wait. Over the last few years, cyanoacrylate glues have become more common. This means that we no longer have to wait days or even hours to fill these small holes. With a good tinted CA glue, you can fill these small holes and be ready to finish in just a few seconds if you know a few tricks.
During this article, I’m going to assume that you’ve already cut the wood and are almost done sanding to whatever grit you want to finish with before applying a finish. Filling these small holes is easy, but you need to do some preparation first to make sure you do well.
The first thing you’ll want to do is figure out which holes might go all the way through the work piece. if you don’t do this step, the piece might be stuck to your work bench for good. In order to do this, you’ll have to flip the piece over a lot. You’ll need to cover up any holes that might go all the way through the piece with a small square of blue tape. There are a lot of holes on the bottom of the workpiece, and they could be several inches apart from one side of the workpiece to the other. I’ve found that it’s best to just cover all of them with tape.
As long as there are no holes on the back, I like to fill each of the holes on top with a little sawdust. It doesn’t have to be maple sawdust, and I just use what I have inside my random orbital sander. You don’t need a lot either, just enough to fill in the hole by a few millimeters. Throw a bunch of dust on top of the hole and work it into the hole with your finger.
All the holes have been filled with sawdust. Then, I use the slightly rounded end of a pencil to push the sawdust further into the holes. In order to make the holes look like holes when the piece is done, I do this: As you push the sawdust down into the holes, you’re making a plug inside the beetle’s little tube. How far you push sawdust is not important, and what you can do with the tip of your pencil will be fine.
My favorite way to fill in insect holes is to use black or brown-tinted CA glue because it looks more like real wood than clear CA glue. That said, clear CA glue will work just as well as the clear version. If you work with a lot of insect-damaged wood, it won’t break the bank to keep both bottles on hand.
To get more control over where I apply CA glue, I use Mitrapel’s Micro Tips. With a little acetone at the end of the day these tips clean up well and can be reused a few more times, which makes them even better value when precise application of the glue is needed.
The first thing we do with the CA glue is soak the sawdust plug we put in the insect hole. You don’t have to fill the hole all the way in right now. I find it best to add a single drop of CA glue to several holes, then spray a quick mist of Mitrapel Activator to quickly harden the sawdust plugs with the Mitrapel Activator.
It’s OK to go back and add a few more drops of CA glue to each hole after you’ve already filled them in. This will make the CA glue stand a little above the work surface. I usually do this in groups of three holes in ambrosia maple because that is how they are usually grouped. You can fill several holes or groups of holes at the same time. Make sure you know that the CA glue can fall a little when its surface tension is broken when it is sprayed with activator. These little CA glue domes may flatten out, and they may not be as tall as you want them to be. Give the CA glue a few more seconds to dry, then add another drop of CA glue until you have a solid dome of CA glue that is a little above the work surface.
I’ve also had what I call “CA glue bloom,” which happens when I don’t fill in a hole with sawdust before I fill it in. A lot of CA glue will flow through the insect tubes, and as the glue heats up and hardens, it will push itself out of any small gaps in the wood that follow the tubes. This is very rare, but it usually happens with “fast” CA glue formulas that make more heat when they dry. The finish sanding will take care of this, so don’t worry about it. To avoid this, fill bigger or deeper holes in stages instead of all at once.
With the holes filled and cured, I usually let the work piece sit for a minute or two while I re-fill my coffee and do other things. Before long, I can be sure that the CA glue has set and I can start sanding. Start with 120, or 150-grit sandpaper, and work your way up to 220. In order to polish CA glue, I will start with 400-grit paper and work my way up through standard micromesh pads and Novus acrylic polish until I reach 800-grit paper. I will then finish with a glass-like finish.
Make sure you flip your project over and remove the blue tape that’s covering the other side of the beetle holes with blue tape. If you need to fill in these holes with more CA glue at this point, you can do that, but that may not be necessary for every project.
It’s important to know that CA glue will get into the wood fibers near the hole’s entrance and around the insect tube inside the wood. The wood finishes that change the color of wood, like stains and dark oils, could leave streaks in places that haven’t been sealed with a cellulose sanding sealer first. This can happen if you don’t seal the wood with shellac or cellulose sanding sealer before you start sanding. The CA glue will still stick to the wood when the sanding sealer has dried.
The next time you’re building something, I hope this quick tip helps you. It doesn’t matter if you want to fill in insect holes with a medium or thick CA glue from Mitrapel. They also make clear and black glues, so if brown isn’t your thing, they also make clear and thick glues. The black works well with dark woods like walnut, while the clear works well with clean maple or birch. Brown looks great in woods like ambrosia maple, carolina cherry, and a lot of other woods that have brown, pink, orange, and red undertones, like oak and maple.
