When to fill a knot with epoxy? Is it always necessary?

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Forum topic by Dagobah posted 03-15-2017 12:15 AM 1784 views 0 times favorited 11 replies Add to Favorites Watch
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80 posts in 1712 days

03-15-2017 12:15 AM

I’ve seen plenty of videos about filling knots with epoxy, but haven’t seen anything addressing when to fill. Is it always necessary?

I’m building a couple floating shelves for our kitchen. One of the boards has a knot with a crack partially through. Do I risk the board being unstable if I don’t fill the knot, or is it something I really need to worry about? It’s just a shelf after all.

11 replies so far

View Madmark2's profile


2476 posts in 1637 days

#1 posted 03-15-2017 12:23 AM

Pine has knots & sap. If you’re not going to plane it should be ok.


-- The hump with the stump and the pump!

View Dagobah's profile


80 posts in 1712 days

#2 posted 03-15-2017 12:25 AM

Pine has knots & sap. If you re not going to plane it should be ok.

This is a 1.5” thick piece of walnut. I’ve already planed and sanded, ready for finish. Just now realized I should double check leaving the crack before I went any further.

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80 posts in 1712 days

#3 posted 03-15-2017 12:28 AM

The knot in question:

View johnstoneb's profile


3167 posts in 3222 days

#4 posted 03-15-2017 12:38 AM

It’s your choice. If it is going to be exposed might leave it alone or fill it with a colored epoxy to draw attention to it your choice. The only time you really need to glue or epoxy a know is if it is loose.

-- Bruce, Boise, ID

View Dave Smith's profile

Dave Smith

94 posts in 1513 days

#5 posted 03-15-2017 12:43 AM

Walnut is a very stable wood. Should be ok unless subjected to extremes of humidity and temperature. That is a beautiful piece of wood! I’m not sure of scale/size from the picture, but have you considered a small butterfly of a complementary wood. Might look nice.

-- Dave Smith - If our phones fall, we panic. If our friends fall, we laugh.

View papadan's profile


3584 posts in 4417 days

#6 posted 03-15-2017 01:31 AM

I leave all knots as they are, just natural character.

View DirtyMike's profile


637 posts in 1951 days

#7 posted 03-15-2017 02:03 AM

I would advise against using a dutchman in a knot. you could be left with a mess in a hurry. I mix up copper powder and walnut sawdust to fill my walnut cracks and knots.

View RogerM's profile


807 posts in 3448 days

#8 posted 03-15-2017 02:47 AM

I fill cracks in black walnut knots with epoxy mixed with lamp black.

-- Roger M, Aiken, SC

View RobS888's profile


2829 posts in 2894 days

#9 posted 03-15-2017 02:53 AM

It wouldn’t take that long to fill it with epox and sand. I fill all cracks with epoxy before milling.

-- I always knew gun nuts where afraid of something, just never thought popcorn was on the list.

View HokieKen's profile (online now)


17226 posts in 2187 days

#10 posted 03-15-2017 05:10 PM

For me, it depends on whether the crack is confined to the knot. In other words, could you remove the knot with a chisel cleanly and if so, would the crack be gone? If not, I like to fill the crack to try to prevent further checking.

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

View HorizontalMike's profile


7915 posts in 3963 days

#11 posted 03-15-2017 05:24 PM

This is what I did on a walnut box. I saved sawdust from my cuts and mixed it with TB-3 and used it as a filler. Since the sawdust was from this piece of wood, it worked out well.

While it did not end up perfectly smooth, it did/does take the emphasis off of the crack and it blends well. Just my 2-cents worth…

-- HorizontalMike -- "Woodpeckers understand..."

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