Clear Filler for Worm Tracks

Advice on clear filler for wormholes in an old walnut piece with character. April 10, 2008

I'm looking for some advice on filling worm tracks in wood that is destined to become a table. The wood is black walnut. There are some interesting worm tracks completely through the 2" thick slab I am using for the top that I want to preserve, but fill. I am looking for something that is pourable, clear, has some elasticity, is sandable, and can fill voids bigger than 1/2". I am assuming that the filler needs to go before anything else, to ensure the best possible bond with the wood.

The end finish I am putting on is a walnut oil and tung oil blend. I am using a natural color stain ahead of the oils. I am considering doing a nice coat of epoxy to fill in some of the minor ticks and such so I can get that super-smooth finish folks love.

Forum Responses
(Finishing Forum)
From contributor C:
Best bet would be a thin epoxy system like West brand marine epoxy - you can add colorant to it or even walnut sanding dust to color, and they also have additives you can use for easier sanding once cured - but my main concern is more why you've chosen to use a non-drying oil in conjunction with a drying oil with the best possible coating properties? Save your walnut oil for salad dressing. Use pure tung oil instead. If you still insist on using the walnut oil, please explain why?

From the original questioner:
The client and I want the filler to be clear, so we can actually look into the wood. No color or additives, though lord knows I've got black walnut dust to spare. I was considering using some walnut oil simply because the wood is walnut, no other reason beyond that. I have tung oil ready and waiting. In general, is there a compatibility problem using tung oil over epoxies? I could see how using a thin coating of epoxy to fill in minor gaps could be problematic for the overall application of tung oil. My primary concern is those areas that really need filling from the worms and beetles of days past and some sloppy, though character-building, chainsaw millwork.

I looked at West Marine's website and at all products they have associated with epoxy and did not really see something that fits the description I am looking for: pourable, clear, some elasticity, sandable, and can fill voids bigger than 1/2". Perhaps epoxy is not what I am looking for...?

From contributor C:

Then let me suggest this. Use b-72 acrylic from Kremer Pigments in NY. It comes in a solid pellet form and you dissolve it in appropriate solvent - this way you can make it as thick or thin as you desire. It is beyond crystal clear and will not yellow with age. It is permanent, but can be redissolved in its original solvent (thermoplastic). It is used as a consolidant in wood conservation and has all the characteristics you're listing here, plus it is not expensive - especially for the amount you would need.

As for West System, no! Plus it would yellow with time, so don't use if you want clear forever. One drawback I think you'll find on any clear filler is that it will stand out as to the rest of the surface, but if this is acceptable, then go with it. There are no compatibility problems with tung and epoxy or acrylic or polyester. It will build a film over any of them, but as I say, seeing the filler will be smooth and plastic - it will stand out from the rest of the surface. You could take a hot exacto knife to the acrylic and imitate the grain, which I do when touching up an oil finish with BI sticks, if you want, but in your case you may not want the distortion from this process.