Filling Knots with Epoxy

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Some of the most amazing pieces of wood are the ones that have “defects.” Defects could be spalting (mold), small checks, bark inclusions or, in this case, a huge hole. Sure, we could cut around those things and eliminate them, but I’m a huge fan of including this character in the final piece. I think it helps make my projects unique, and capitalizes on the natural beauty of wood. So, let’s look at filling knots with epoxy.
THE RESIN
The product that will give us the best results for filling knots with epoxy is casting resin. This is very different from the two-part epoxy in a syringe you’d buy at a home center or hardware store. It flows better, and it cures more slowly, so you have more working time. Be sure to carefully follow the manufacturer’s directions for mixing. You’ll probably have bubbles in the resin after you pour it. No problem, we show you how to get rid of those.
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THEN WHAT?
Once the resin is poured, give it ample time to cure. It cures much more slowly than off-the-shelf epoxy. Once it’s completely cured you can sand it flush with surrounding wood, and admire your work.
OTHER USES FOR EPOXY
In addition to filling knots with epoxy you can use it to fill or bridge other defects. Lots of woodworkers are commonly using epoxy for wood cracks. Again, instead of cutting the defects out, we can make them an interesting part of the finished piece.
GENERAL REPAIRS
If, instead of highlighting defects like cracks, you want them to go away, check out our advice on how to repair wood cracks.
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[@DrifterSpirit9]

I would definitelly wear a mask specially when sanding epoxy

[@billrobinson8939]

First video of epoxy pours out of at least 50 I've watched where bark was saved. Always horror stories of leaving the bark, which I love. Thanks for that info.

[@MikeBramm]

When I finish mixing the epoxy I pour it into a plastic bag then cut the corner off the bag so that I have better control pouring the epoxy. Once finished, I leave the bag by the project so that I can determine when the epoxy has finished setting. Once the bag is hard as a rock, I know it's done and I can start sanding the project.

[@XatxiFly]

Thanks, might steal this!

[@robertweakley8839]

Very smart

[@robertweakley8839]

Wish my brain worked like that

[@MrBigMalT]

What a very helpful video thankyou. I would have loved to see the board after sanding to the final grit and with a finish on!

[@hardnox6655]

Good demonstration. I use epoxy daily for the same applications using West Systems Epoxy. I found that using Gorilla tape works much better than the blue painter's tape. It's important to burnish the tape for a good seal. The heat from the epoxy often releases the blue tape resulting in a mess. Heating the wood with a heat gun BEFORE pouring the resin in the void improves resin flow and decreases the volume of air bubbles.

[@kennethover7259]

Can you put the tape on the top face and pour from the bottom side? Wouldn’t the bubbles then move to the bottom? I’m still new to this so...

[@hardnox6655]

@@kennethover7259 Excellent point. However, you'd need to leave some extra room as it would most often result in a shallow concave surface.

[@enyaw1948]

Wish you had shown the finished job so the viewer can see the results of how well the product worked

[@shoshanachurch3150]

I agree!!

[@lkj974]

I have watched about five of these epoxy filling videos. They always wet it with mineral spirits at the end “so you can see how it will look”. Every single one. It looks like it will look when you have put finish on it. What is the matter with these guys?

[@GoldenGateNum9]

It is a very beautiful piece of wood. Thanks a lot, I actually didn't know the difference between the two resins, one is rapid set the other is more workable for longer, I personally go head over heels for Beech wood =), thanks again.

[@johndillon3942]

Thanks, just what I needed to know. Building a table in my bay window, with some knot hole voids (by choice). Love that look too. Everything always reads that it's the best thing since shirt pockets and sliced bread, but to hear someone say "casting epoxy", no brand and to watch them perform the task, makes life simple for me. Been woodworking for a long time, but always, always, always researching for new, possibly better techniques to "Get R Done ". Oh, your sound affects, were spot on, too. Thanks again John

[@missingno777]

Good video, but dude! Wear a dust mask! Wood dust is one thing, resin dust is another.

[@jgriff19861947]

Thanks for the tips on the epoxy.

[@LittleTreeBlue]

This was super helpful! - I do wish we’d been able to see the finished board…

[@IcedReaver]

Great idea using heat to dissipate epoxy bubbles, thanks for that!

[@harvey648]

Never knew about heat to remove the bubbles. Thanks for the tip!

[@kevinwolukis9984]

I'd recommend a butane torch a heat gun essentially blows hot air which could add dust particles.

[@joelbodder9671]

Can you use stain and polyurethane to finish the wood after you fill the cracks with the epoxy?

[@carlieslongbottom2553]

If you have sanded it, it won't be clear it will be hazy, will it not? You didn't show the finished product. Did you perhaps use a torch to reheat and get rid of the haze?

[@EricInTampaAcoustic]

I’m thinking about using this to fill some wood flooring gaps

[@RobertSmith-zn5zc]

I really liked this video and I want to start doing some of that. But on a somewhat unrelated subject I want to ask you a question. I have that same Bosch random orbit sander. However when I use it the sander kicks and bucks like crazy whereas when you use it its seems to operate smoothly. Do you have any idea why mine would be different?

[@carolinabooboo]

thanks for the video, I'm going to fill some cracks in a old butcher block, really thick, I'm guessing this casting resin is the way to go ?

[@CarolynCrescio]

Can I use this method on old, cracked teak patio furniture?

[@RobyWanKenobi]

Any suggestions on preventing black tinted epoxy from soaking into unwanted grain?

[@frederickwatson557]

George, you must have been blowing your nose like crazy breathing up all that dust as you used the belt sander! I'm surprised you didn't put a hood or respirator on.

[@richardhester6877]

I never seem to be able to get a good seal on the bottom with masking tape, gaffer tape, duct tape, etc. There always seems to be massive leaks even with big overlaps. Any suggestions?

[@Wwgoa]

Hi Richard. I haven't had a problem with this, but I'm guessing that you are not getting the wood clean enough before applying tape. Any tiny particles could potentially cause an adhesion problem. Thanks Paul-Woodworkers Guild of America

[@kevinwolukis9984]

Gorilla tape

[@MegaJohnny80]

Tuck tape

[@nitrousblast1]

Just curious because I’ve had this issue. Did you seal the wood before you put the epoxy in the cracks and voids? The epoxy I used soaked into the wood and created deep stains on the surface around the filled cracks I can’t get even sand out. The piece is ruined. How did you avoid this issue in this project?

[@PetesShopMakes]

Could you run the board through the planer once the epoxy has cured or is there an issue with the epoxy damaging or dulling the blades at all?

[@dmcwoodworx2968]

I tried that last year, on my helical head planer. It worked fine.

[@pcicchin]

I've done with the stock blades on my dw735X, and it works quite well.

[@PetesShopMakes]

@@pcicchin is that the 12in dewalt lunchbox style planer or the next model size up? 12 1/2 or 13 i think? I forget the model numbers but I have the 12in model so I assume it would work fine on that as well with the straight 3 blade head on it.

[@pcicchin]

@@PetesShopMakes Pete, it's the larger, 13', one - you access the blades from the top, instead of the outfeed side. I don't see any reason why the smaller, 734, wouldn't do the same - the only functional difference seems to be the height adjustment mechanism. [e-mail]

[@PetesShopMakes]

Paul. yes i beileve you're right but correct me if im wrong but doesnt the 13in model you own also have an adjustable speed setting for finish passes in addition to the standard roughing pass like on most lunchbox style planers like mine. Im curious to know and wonder if that would give better results as well with the epoxy or if it doesnt make any difference whatsoever between the two. have you any experience in doing that?

[@charlesgoff6429]

What grit of sandpaper on the belt sander?

[@daviddejulio863]

How will stain interact with the epoxy? Will it look horrible like glue left behind? I'm sure not because I know this is a common use for many different finishes but I'm just curious of the mechanics behind why it doesn't stick out like a sore thumb during the finishing process compared to glue.

[@Wwgoa]

Hi David! I have forwarded your question to our experts. Our experts will reply directly here. Please allow 1-2 business days for our experts to respond. Thank you!

[@Wwgoa]

Resin doesn't accept wood stain very well after it has cured. If you are looking for color-matched approach to filling knots using resin, you'll want to add a dye to the resin before it cures. There is a lot of content on the wwgoa.com site about this process. It's very difficult to color match this way, however. Resin works better as an accent color rather than a match to the surrounding wood. Paul

[@franks471]

What is the difference between regular epoxy and casting resin? Will the casting resin also act like glue? I think this is going to be hard to describe but i'll try. The project I'm working on, I have an electric guitar with an unstable "bolt-on" neck joint. I've fixed this neck in place using metal rods and made it so the neck rests inside the pocket on four solid, level corners. Everything is lined up right and it's ready for the glue, but I want to make this like a set neck guitar *without removing the neck again* in order to glue it. There are voids under the neck and on the sides, and an opening where I can pour the epoxy. My plan is to mask off the places where the epoxy can leak out, and pour it in through the opening I have chosen through a funnel. I never want this neck to shift again, or ever have it removed. The plan is to have it refinished as a "one piece" instrument.

[@Wwgoa]

Hello. This is a really unique application for epoxy. My gut is telling me the standard two-part epoxy off the shelf from a hardware store would give you what you need, but it’s probably too thick to pour into place. My advice is to talk to a real resin expert, like the folks at TotalBoat www.totalboat.com/ They have a wide array of products and really know their stuff. Describe your needs to them, and they’ll get you in the best direction.

[@gerrymurphy9524]

will this work for larger holes, like 3-4 inches?

[@Wwgoa]

Yes it will. Thanks

[@brettbradley2572]

Hi there, I have a slab that, on the bottom is too big for masking tape. Kinda like a bullet entry, and exit wound. What can I do to block the back side?

[@kevinwolukis9984]

A thin piece of plexiglass would work great.

[@packerbacker4315]

I have a deck post has a big knot hole. Anyone know a good way to fill a vertical post with epoxy?

[@christyfortes2275]

Since the non casting epoxy in the syringe applicator is thicker, I would go that route.

[@yesmayhem2124]

Could you use epoxy to fill in that gap at the outside corner? How would it be braced?

[@Wwgoa]

Hello. Yes, you could. You could frame it up with a wood brace lined with wax paper, or tape if it was small enough. Anything that can hold the epoxy in place while it cures. Thanks Paul-Woodworkers Guild of America

[@mattmonaghan5502]

What gets rid of bubbles isnt heat but Co2.

[@fredricbethune7803]

Should never use blue tape. Use Tyvek tape and it never leaks.

[@tjerkheringa937]

And you never sand epoxy without a face mask and proper ventilation.

[@shantelfullerton9865]

Make it wooden with the help of the Woodglut instructions.

[@kawonnowak]

What no mask??

[@chrisperry5129]

You should probably have dust collection or at least wear a mask silly

[@zacharycollins6548]

Wear a mask when you're sanding epoxy.

[@EricInTampaAcoustic]

I’m thinking about using this to fill some wood flooring gaps

[@EricInTampaAcoustic]

I’m thinking about using this to fill some wood flooring gaps