If you’re a woodworker who works with live edge slabs, turning blanks, burl wood, or spalted wood, then there’s a good chance that you’ve had to deal with punky wood. Punky wood can definitely pose problems because it is soft and porous, but with a bit of work, you can transform it into a unique quality in your finished piece.
This picture shows a maple burl with punky wood on the left and the regular wood on the right. The areas are defined by a black spalt line followed by darker wood where the fungus is moving into the natural wood.
What is Punky Wood
Punky wood is wood that has begun to rot and turn soft. Although woodworkers often use this word to describe any part of the wood that has already started to turn soft from decay, insects, bark inclusions, or anything else.
Punky wood is usually found towards the center of trees that have begun to rot and will not always be noticeable when looking at a standing tree or log.
The softness of punky wood can vary wildly from slightly soft but still workable as is to wood that disintegrates as soon as you touch it.
Punky wood, when handled correctly, can add a nice touch to finished pieces as it will often have spalt lines in and around it and will turn a darker color than the rest of the wood.
Woodworkers who work with full slabs will often run into punky wood and deal with it either by hardening it or removing it entirely and filling the void with epoxy.
How to Work with Punky Wood
The picture below is from part of our dining room table that I made from a slab of butternut. One side had an area where a branch had been cut, and the tree grew around the wound.
Over time this cut area had begun to rot, leaving an area of spalted, punky wood with some voids that needed to be filled.
Hardening Punky Wood
This part of the slab needed to be filled in in some parts and hardened in others.
To show you how soft this area was, I could easily break off chunks of the punky wood with my fingers, so there was no way this could be left as is.
Hardening punky wood can be done with a few different products.
- Epoxy resin
- Cactus Juice
- CA Glue
- Wood Hardener
Each option has its pros and cons, so we’ll take a quick look at them.
Epoxy is probably the most common way to fill in larger areas of punky wood. Note, though, that this process is different than stabilizing the wood. We’ll discuss wood stabilization next.
I like to use a thin, slow-curing epoxy as it can take quite a while to work its way into the punky wood. If you use a thicker or quick curing epoxy, you’ll end up trapping a lot of bubbles inside your piece.
For punky wood with larger voids, I like to use Deep Pour Super Clear Epoxy, and I will heat it slightly in a bucket of warm water before mixing and pouring. This helps increase the viscosity and reduce the chance of bubbles getting trapped.
I will also paint a thin layer of epoxy over the bottom of the voids and let it partially cure. This helps seal the wood, so it releases fewer bubbles during the deeper pours.
On punky wood with no voids, I either brush in epoxy if it’s not a flat form or pour it on the piece and move it back and forth over the punky area with a silicone scraper. This helps push the epoxy into the punky wood, which will help strengthen it.
As bubbles are released, you can run a heat gun or torch over the top of the epoxy to pop them.
Stabilizing punky wood with cactus juice requires a different process than regular epoxy. With epoxy, you pour the epoxy on top of your piece, then let it soak into the wood. Depending on how punky your wood is, it may soak all the way in but often; if the wood is thick enough, it will stay closer to the surface of the wood.
This creates a nice, solid surface but still leaves softer wood inside the piece.
The wood is fully submerged in cactus juice and then put into a vacuum chamber for around 90 minutes with cactus juice. The blank is then baked for another hour which fully cures the resin. This ensures that the resin is fully absorbed into the wood, which creates a totally hard blank all the way through.
For smaller blanks that will be used for pens or knife scales, this is a great way to turn really unique but otherwise unusable wood into stable blanks.
CA glue is an excellent option for hardening punky wood on smaller pieces. If I’m working on small woodturnings or pieces with tiny areas of punky wood, I’ll dab on layers of thin CA glue. I like to let the glue set for a few minutes rather than immediately spraying on the CA accelerant.
This lets the glue absorb into the punky wood and lessens the chance of it bubbling up when the activator is applied.
If you have areas of punky wood with some voids, you can step up to using a medium viscosity CA glue to finish the job. This will help fill in any areas the thin glue may have missed.
I have been a big fan lately of the Starbond black CA glue. The black color blends in nicely on darker woods, and it’s also great for filling in knot holes, tear out, etc.
A few commercial wood hardeners are marketed towards hardening punky wood in areas around the house, like windowsills or frames. Generally, the idea behind these hardeners is to strengthen the wood, which can then be filled, if needed, with wood putty and painted.
These hardeners work perfectly well on wood projects also! Although they can be a bit more noxious than working with epoxy or CA glue.
One of the most commonly found wood hardeners on the market is Minwax Wood Hardener.
This fast-drying wood hardener can be painted onto the punky wood with a disposable brush. Then within 2 – 4 hours, it will be fully cured and ready to work.
Turning Punky Wood
Running into punky wood can be a pretty common occurrence for woodturners. As we’re often after unique pieces of wood (read: found on the side of the road), that means we’re usually dealing with some imperfections during the turning process.
Turning punky wood can turn into a somewhat regular occurrence, but with a bit of tool and material prep, the process can be pretty smooth.
When turning punky wood, it can have a tendency to tear out when wet. This can be a problem in softer woods like birch and requires keeping a very sharp tool and taking shallow passes. If you’re just rough turning the piece and leaving it plenty thick, this shouldn’t present too much of a problem once you finish the piece, but it is still nice to leave your future self a smooth blank to start with.
If tear-out is a problem during your final turning, applying CA glue layers can help harden the surface enough to get a clean cut.
The final piece can then be hardened with CA glue or a wood hardener before finishing or just be left natural if the punky wood isn’t too soft.
Sanding Punky Wood on the Lathe
Sanding punky wood on the lathe can lead to issues as the punky sections will typically sand down far quicker than the harder areas of wood. This can lead to the piece going out of round. Adding CA glue to the punky areas can help keep it consistent with the rest of the piece.
If you’re comfortable with a slightly out of round shape, then sanding on a very slow lathe speed with a sanding pad on a drill or orbital sander should do the trick as well.
Finishing Punky Wood
The state of the punky wood on your finished piece will ultimately dictate the best finishing methods for the piece.
If you have taken the time to harden the punky areas with epoxy or CA glue, then you should be able to finish the piece with whichever finish you prefer. I typically use wood butter on all of my pieces, although it can soak in a bit more than I would like on punky pieces, which can leave a blotchy finish if the wood has been hardened. Still, this isn’t an issue at all.
On pieces where the punky wood is still soft, you can apply a coat of sanding sealer or a finish with multiple coats like polyurethane. The polyurethane will build up a hardened coat of finish over the punky wood, which will help protect it from damage going forward.
Burning Punky Wood
If you’re one to burn your wood scraps, then have no fear of burning punky wood. The wood won’t burn quite as well as regular wood as the wood structure has begun to break down. This means it burns a lot faster. You don’t have to worry about putting off any noxious fumes, though, as the fungus in the wood will burn off.
Derek grew up woodworking in his father’s shop and has since gone on to start up a successful woodworking business on Etsy. In his spare time, you can find him mountain biking, skiing, or writing.