Repairing small walnut cracks

[Brent VanFossen]

I found and bought a highly figured walnut board that I plan to use for making a tea box for my wife for Christmas (shhh!). When I resawed it to thickness, I found several cracks on the previously hidden surface that I need to repair. These surfaces will be on the interior of the box but I would still like them to look nice. Photos are attached.

I have saved some of the walnut dust from cutting these boards and can use it for coloring whatever filler I use in the cracks. This box will not see much stress. I'm wondering what epoxy or other material would be appropriate for filling these cracks. The boards are approximately 4x15 and 4x10.

Thanks for the help.

Brent

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[Brian Ashton]

Any epoxy will work. If its 5min stuff youll have to work faster thats all. And make sure the dust youre using is really fine, for both looks and ability to push it deep into the cracks

[Jay Pugsley]

Are these affecting the structural integrity of the wood? If not, my preference would be to leave them as is. I like the look of wood in it's natural form, with flaws like these adding to the beauty. In fact, I would make them the outside of the box. But, these are just my preferences.

[David Dalzell]

For small cracks and/or boo boos in joinery I have had success in mixing fine (matching) sawdust with shellac and sanding the wet paste into the defective area.

[Pat Barry]

Are these affecting the structural integrity of the wood? If not, my preference would be to leave them as is. I like the look of wood in it's natural form, with flaws like these adding to the beauty. In fact, I would make them the outside of the box. But, these are just my preferences.
I tend to agree with this however, if you really want them filled I would rather see you use a clear epoxy (no filler dust). That way you will keep the natural look and still have a smooth surface when you are done.

[glenn bradley]

I also use epoxy and tint it as required to blend into the finish I plan to use (clear is sometimes the answer). My additional concern is that they appear to be in an area that may be used for joinery.

[Prashun Patel]

Those cracks look small, so clear epoxy may be ok. But I've found that epoxy can dry with some bubbles in large gaps or can dry to an opaque yellow if not mixed absolutely perfectly. So, on cherry and walnut, nowadays, I always place a drop of black ink or transtint dye in the epoxy. It darkens it and makes it opaque. I find it looks at best like it's natural, at worst, like a good, intentional accent.

If you are not planning to dye the wood after sanding, then you don't need to seal the wood beforehand; just let the epoxy set in, and then scrape off the excess after dry. Personally, I prefer slow-setting epoxy because it gives it ample time to settle down into crevices.

I find CA glue to sometimes dry brittle and hazy.

[Mark Gibney]

I sometimes add a little alcohol to the epoxy so it flows into the cracks easier. I think air bubbles can come out of the thinned epoxy easier too.

[Patrick Chase]

I sometimes add a little alcohol to the epoxy so it flows into the cracks easier. I think air bubbles can come out of the thinned epoxy easier too.

The emphasis here needs to be on "a little". IIRC the upper limit for the epoxy to still harden properly is about 5%. Also alcohol is the worst of the 3 common epoxy thinners (acetone, lacquer thinner, alcohol) in terms of strength/viscosity tradeoff. By that I mean that alcohol yields the lowest cured strength at any given viscosity (or conversely the highest viscosity at any given target strength). I know one of the 3 discolors the epoxy, and I know it's not alcohol, but can't remember which.

You can always thin epoxy by heating it...

[Brent VanFossen]

Thanks for all the responses. The cracks don't seem to affect the soundness of the boards, despite some of them being in the joinery area; for my hidden spline joints, I don't think they will affect the strength much. I may just stabilize the cracks locally and otherwise leave them natural.

[Erik Christensen]

for me - epoxy is for the big defects - those look small enough that I would ignore them - if after a base finish coat I decided to go for a smooth surface i would use a couple of coats of clear grain filler - i find that a lot easier to sand & get perfect than a single coat of epoxy and it will not impact any stain/dye you want to use as it goes on later

[James Waldron]

I sometimes add a little alcohol to the epoxy so it flows into the cracks easier. I think air bubbles can come out of the thinned epoxy easier too.


Noooo! No alcohol, please. Makes a big mess and degrades the quality of the epoxy. Your wife deserves better.

And as to heating the epoxy, that works, but an even better approach is to head the wood (heat gun to warm, not hot) and that will draw the epoxy into the crack as it cools. Reduces the epoxy viscosity while warm to provide excellent flow. If you heat the epoxy itself, you'll accelerate the cure reaction and reduce the working time. Warming the work will accelerate it too, but that's okay when it's already in the crack.