Recommend an epoxy for live edge cracks/knots

[Wes Billups]

I am building a waterfall desk for my daughter using a slab of Kentucky coffeetree. It has some very minor cracks/checks/knots that I would like to fill and stabilize since it will be a desk surface.

I've looked at our local home centers and don't see any epoxy that looks like it'll work for filling these voids. They all seem way too viscous for this purpose.

Can someone recommend an epoxy that can be purchased at a local home center (Home Depot, Lowes, Menards) or Woodcraft? These are my only options as I will be near a Woodcraft on Friday and want to complete the woodworking portion of this build this weekend.

Any pointers would also be appreciated.

Thanks in advance for any help and if you have some examples of projects you've used epoxy to fill voids please attach those to your reply.

Wes Billups

[Jeff Heath]

You can get yourself into some trouble using home center epoxy on a job with this much time invested. Not a good time for going cheap, as the wrong epoxy can wreck your project with air pockets and poor drying. There are lots of products available for specifically this use, and they aren't sold at a home center. If you have a marine store around, you can check there. I don't know what Woodcraft sells, but I use system 3 two part epoxy for this with very good results over a long period of time.

Bowties installed along a crack in the top approx. 15" long. Invisible.

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This table was made from bookmatched slabs that were filled with loose knots, and the crotch wood was badly cracked. Filled in nicely. 15 years old.

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Hope this helps you

[Richard Coers]

You can lower the viscosity by placing the resin in warm water before mixing. You could use casting resin if there is a Hobby Lobby near by.

[Robert Engel]

I use West systems epoxy for filling cracks.

Bubbles can be an issue with thicker epoxies. A heat gun will help smooth it out.

[John Blazy]

Always heat the wood with a heat gun just prior to applying epoxy. Does a world of help for a ton of reasons. When doing large cavity pours, pre-apply epoxy as a seal coat and wait for it to partially cure (super thick and tacky, but not hard, not liquid), then pour new - will eliminate bubbling.

[Prashun Patel]

I use system three. It sets slowly so it settles. You may need to apply multiple coats on large voids.

I prefer to dye black. It eliminates imperfections and bubble appearance and looks imho most natural.

[Andrew Nemeth]

I just filled about 2500 sqft of character/rustic grade white oak flooring. I used system 3 general purpose resin and medium hardner purchased from my local woodcraft store. They also sell another system 3 epoxy called mirror cast, which is made to be crystal clear and have less air bubbles (iirc) but sells for a bit of a higher price.

In view of the higher priced alternative, I chose to use the general purpose resin because I wanted to heavily tint the resin, add a thickening agent to make a paste for some very large voids, and I prefer the look of the finished knots with color variations that are added by using a slightly different shade of filler to fill in the air bubbles at the surface after the initial sanding. In other words, the benefits of using the mirror cast finish for me were minimal, and the air bubbles I could impart into the resin when I wanted to, were beneficial to me.

Without adding the colloidal silica densifier to thicken the resin, the general purpose resin would easily flow into very fine voids such as checks. I also noticed not too many bubbles in fine checks when I poured “clear” samples without the silica. If I were only filling small checks and voids, even if I wanted a clear look, I would not hesitate to use the general purpose resin. The amber hue from the medium hardener is so slight, I’m not sure I could distinguish it as amber on all but the whitest of surfaces. On the other hand, if I were pouring deep voids, and wanted a clear as water (non-amber) look, without entrained bubbles, I would certainly entertain spending the extra money to try the mirror cast from system 3.

Side note: if you plan on buying system 3 metered pumps, make sure you really look at the pumps and the caps on your resin and hardner. System 3 recently changes threads on some of their resins and hardners and the old pump set labeled for all bottle sizes will not work with the smaller necks of some of the newer bottles. I called system 3 and they were extremely helpful for both technical questions and to address my pump issue. They sent me a replacement pump to fit my smaller bottles, but it was not calibrated to the larger pump so that an reasonable ratio of pumps (ie 1:1, 1:2, 1:3) could be used for the mix. Since I was mixing up larger amounts, I just ended up using the graduations on some mixing cups. If you are only doing very small batches, you may need to weigh it if you are trying to be precise (which is less important in non-structural situations) to avoid improper hardening.

[Wes Billups]

Thanks for all the input. Woodcraft sells the System 3 so I think I will go this route.
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They also sell a black colorant which I agree with Prashun on looking better. I'll plan on picking this up on Friday.

Thanks again for the input.

[Prashun Patel]

Instead of the System 3 epoxy pigment, get a 2oz bottle of Transtint black. The Transtint is versatile and useful for so many other things, including ebonizing.

You will only need a couple drops per ounce of epoxy, so it does not affect the performance of the epoxy at all.

I prefer to use a nail or thin point to drip it into the void. Over fill it. Try to be neat, but don't worry about spills or drips on the surface; it will sand, scrape or plane out. It does not travel too far into the surface.

[John Blazy]

Instead of the System 3 epoxy pigment, get a 2oz bottle of Transtint black. The Transtint is versatile and useful for so many other things, including ebonizing.

You will only need a couple drops per ounce of epoxy, so it does not affect the performance of the epoxy at all.

I prefer to use a nail or thin point to drip it into the void. Over fill it. Try to be neat, but don't worry about spills or drips on the surface; it will sand, scrape or plane out. It does not travel too far into the surface.

Great tip on the transtint. I believe its alcohol based, so it does not interfere with the epoxy cure (alcohol is the best thinner for epoxies, up to 10% only), and so many other uses. Like sharpie pen ink in liquid form.

[JAMES COCHRAN]

I use Bob Smith slow cure(30 minutes) 2 part epoxy from Amazon. Can buy in smaller quantities for those of use that do not use it very often. I am a hobbiest furniture builder. Does anyone else use this product? I tint with a drops of acrylic paint of whatever color I want it to be. Measure it out in little 1 ounce cups I've seen used in hospitals. Agree on heat gun, or if in the summer, put out in the sun if in southern climate. I surround voids with painters tape, pull off when epoxy hardens, sometimes have to use knife to carefully remove. Less sanding of epoxy that way.

[Jacob Reverb]

Most if not all epoxies can be thinned up to 10% by volume with acetone. This should make it less viscous...

Don't forget a UV blocker on top of the epoxy if it doesn't already have one. Otherwise the epoxy will yellow and degrade over time, depending on the UV "dosage" it gets...

[Jeff Heath]

Transtint can be suspended in alcohol or water. I have never even tried any other dye, as I've been very happy with Transtint.

[Neil Gaskin]

Wes, I use west systems. There is a store in Lawrence that stocks it. KC sailing supply. It's in north Lawrence. Mixes well with powder dye if you want to go black or a different color. I like west systems as a good multi purpose epoxy.

[Wes Billups]

Neil, thanks for the source. I just called and believe I'll go with the West Systems as it'll save me an hour of driving and it sounds like the weather on Friday could be poor.

Thanks to everyone else for the suggestions and ideas. I do have some darker transtint dyes so I'll just use these with the epoxy.