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TL;DR: How do I fix this, and have it match the final color?

Void in wood

I'm getting ready to join some 10.5"-wide red oak for a table top, and one of the boards has a void on an edge, right in the middle (length-wise). It's a gorgeous piece otherwise, and I have a limited supply of these.

I saw a Wood Whisperer (love that guy!) video where he used a tinted epoxy to fill in a knot. That seems like a reasonable approach, but I'm not sure how that's going to work with the final stain / treatment that my wife insists on using. (It's some sort of tea-based mixture that gives a gray-ish weathered appearance. She's used it on some other pieces and it looks ok.)

So, the question!

Obviously, I can't stain epoxy.

  • Should I look for another way to fill the void?
  • Should I remove the knot and patch the wood? It's a very irregular shape (duh), not too sure how that would work.
  • How else can I stabilize this section? It's fine if I still see the knot after it's done, but I don't want a piece that's going to crumble or otherwise disintegrate over time.

Suggestions? Someone else said to replace the knotty section with a bowtie, but I'm not a huge fan of those. I'd love something that would match the grain. But, since this is on the outside edge of the table, I don't see how I could do that and have it either not obvious, or not ugly.

  • I agree with the others basically - these knots tend to look best with either clear epoxy, black epoxy, or something really bright like turquoise-filled epoxy. – aaron Aug 14 '17 at 12:27
  • @aaron oddly enough, turquoise is my wife's favorite color. BUT, I'm thinking black will do in this case. :) – 3Dave Aug 20 '17 at 21:45
  • good choice. It will look very nice once you'd sanded/polished, and finished it all. – aaron Aug 21 '17 at 12:02
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Should I look for another way to fill the void?

This is a matter of opinion but I don't think so. Epoxy is one of the best, if not the best, materials to fill voids and fallen knots. It has become virtually the default choice for this purpose for this reason.

It should be mentioned that a void at the edge of a board does represent a significant weak spot, and if structural strength were important one should be removed, patched or the piece of wood replaced with another more suitable. But for a table you don't really have those concerns and I'd have no hesitation in using this board at the edge of a tabletop.

Should I remove the knot and patch the wood? It's a very irregular shape (duh), not too sure how that would work.

Although the epoxy can stabilise anything loose that's there (it essentially glues it in place) it's probably best practice to remove everything loose before applying the filler. I carefully scrape and then scrupulously dust off a large knot hole with stiff brushes before dribbling in epoxy.

If you did want to patch with wood the patch doesn't have to match the natural void shape. In fact it's been common practice for many centuries to ignore the original shape of a defect and patch in a simple-to-cut replacement piece, as in the classic "Dutchman" patch1.

How else can I stabilize this section? It's fine if I still see the knot after it's done, but I don't want a piece that's going to crumble or otherwise disintegrate over time.

Taste on this may change in the future but currently the most common way this would be dealt with is with a fill (usually epoxy) and I think this is the best approach myself if you aren't letting in a patch.

More on what you can fill and/or tint epoxy with in a previous Answer, Large hole filler products, what is available.

TL;DR: How do I fix this, and have it match the final color?

If you did want it to match the final colour then patching with wood is the only sure-fire way. A fill that very closely matches the final colour of the wood (note that this would have to be done after staining) will still stand out plainly from various viewing angles because wood's cellular structure catches light in a way that filler materials don't. This is why fills look 'dead' and can usually be spotted without difficulty from a distance, hence the long-standing advice to use filler as little as possible.

But I don't think you should aim for it to match. Dark fills (e.g. tinted black or filled with used coffee grounds) have become the norm and can give a very pleasing result2. We're now comfortable with highlighting irregularities and even outright defects in wood, embracing that it's a natural material, which is great as it allows us to use wood for show surfaces in furniture that might previously have been put aside for use in rough carpentry at best, but often consigned to the firewood pile!


1It's hard these days to separate butterfly keys from Dutchmen but they are two very different things. They just happen to be the same shape (sometimes). The classic Dutchman is a cosmetic patch, a butterfly key (as with all keys) is a stabiliser or locking device, used across a joint or a natural crack to prevent movement.

2The fill doesn't have to be dark if your taste doesn't run to that. You could colour it bright red or blue if you preferred. And metal powders make excellent filler material for resins so a bright copper, brass or pewter fill is easily achievable.

  • Now I'm wondering how the epoxy will fair as the wood moves. It's not the most flexible of materials. Also, toxicity - if it cracks as the wood expands and contracts, I could see pieces winding up on the floor (and in a kid's mouth). My gut instinct is that this is a non-issue, but still curious. I think I'll flip the board and put the (filled) void on the interior, anyway. – 3Dave Aug 20 '17 at 22:10
  • @DavidLively Epoxy is quite brittle but the expansion here will be minimal so there's really nothing to worry about — I've never seen a photo of a cracked fill of this sort so in practice it may never occur. As wood expands across its width only, nothing to speak of along the length, it's only the expansion of a few inches of wood (width of the defect) that the epoxy needs to deal with, and max movement there is just a tiny fraction of an inch which the epoxy seems to deal with fine. – Graphus Aug 21 '17 at 7:03
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It's a knot. Or at least you are treating it like a knot. Knots don't match final finish color in virtually all cases.

The basic approach - fill with black epoxy. Trying to be subtle but it won't match - fill with a dark gray epoxy. Tossing subtle out the door, fill with epoxy and turquoise (or whatever) chips, polish it up & make it (more of) a feature.

But my gut reaction to this large of a void on a board that you are choosing to put at the edge of the table is to remove it, or not put it at the edge of the table, or rotate it end for end or top to bottom so the void is not at the edge, at least. I can't tell what percentage of the board is affected, but filling with epoxy is not really a structural repair if the void is more than a cosmetic problem. A void along an interior joint is much less compromising than a void on the actual edge.

For removal, if there's adequate length to the board, I'd be tempted to try a skew joint or a stepped lap joint that approximates a skew joint.

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