Treating punky wood to get a clean final cut

The spalted wood I like to turn for its colorful grain often comes with a down side: soft, punky wood which shows a lot of ‘tear-out’ on end-grain cutting. Because the wood is soft, the cutting tool doesn’t get the benefit of having hard wood ahead of the wood being cut, so the fibers tend to bend on first contact with the cutting edge, and then get torn out instead of being cut, making for a ragged surface.

In the following photo, the wood to the left shows a lot of tear-out. All of this end-grain face of a natural edge bowl was like that, before I applied thinned epoxy to stiffen the fibers. Then, on the final cut after the epoxy had cured (the area to the right of the photo), the now-stiffened wood cuts cleanly, using the same tools and technique as resulted in the tear-out on the left. The final cut shows almost no tear-out.

Area to left (before final cut) shows a lot of tear-out; area to the right shows the beneficial effect of thinned-epoxy treatment. This photo was taken while the final cut being done; I stopped halfway through to take this photo to show the benefit of the treatment. Same tools, same cutting technique, same wood but now treated with epoxy, and the tear-out is gone.

It probably doesn’t matter much what epoxy you use. Mix it according to directions, then add another 25 to 30 percent of denatured alcohol. (So, if you mixed 2 ounces of epoxy, you might add 1/2 ounce of alcohol.) The purpose of the alcohol is to reduce the viscosity of the epoxy, so that the fluid will soak into the wood, rather than sitting on top of it.

Apply the thinned epoxy with a cheap brush or sponge-on-a-stick applicator. Be generous! Sometimes, with a thin bowl, I will see the epoxy emerging on the other side of where it is being applied. That should be enough!

Curing time varies by the type of epoxy used and the ambient temperature. You want it thoroughly cured; as hard as it gets. I sometimes accelerate the cure by putting small items in a toaster oven, set at 120 degrees F. I wouldn’t go higher than that.

Robert started woodturning in 2015, after retiring from law practice and software development work. His woodworking shop, Black Rock Woodworks, is in Clayton, Georgia, where he resides on Lake Burton.