Filler for Countertop Knotholes

Advice on a filler material for knotholes that's compatible with a Tung oil finish. May 12, 2013

What type of product should I look for to fill knot holes in black walnut? I've made a kitchen countertop from 8/4 American black walnut that has several small (1") to large (3 1/2 - 4") knots in it. I will be finishing the counter with tung oil and am looking for a filler that is clear enough to preserve the rustic look of the knotty walnut yet not collect water. I am worried that an epoxy will scratch when sanded and, because the tung oil will not create its own surface as would lacquer, the scratches will be visible.

Forum Responses
(Cabinet and Millwork Installation Forum)
From contributor M:
I have seen epoxy used to fill holes, usually as part of an epoxy finish on a tabletop. Not sure of compatibility with tung oil. Have you considered using a dutchman or other decorative plug to deal with the 3"+ holes?

From contributor E:
We used to mix sawdust of the wood with the epoxy. Worked well, although it does have a different sheen. You can use Bondo and color and then seal the Bondo prior to the tung oil.

From contributor J:
A guy in my shop uses West System epoxy in large voids all the time. His finish is oil/poly hand applied. This looks really good, if you use a torch or heat gun to get the bubbles out of the epoxy while it's curing. You can see clear down through it and it doesn't look different from the surrounding finish.

From contributor B:
A shellac would also work.