filling large void/ cavity in live edge walnut slab

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Forum topic by marc_rosen posted 05-08-2016 03:14 AM 7035 views 0 times favorited 7 replies Add to Favorites Watch
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143 posts in 3355 days

05-08-2016 03:14 AM

Topic tags/keywords: question walnut finishing rustic

Hey Gang, I was asked to finish an 8 foot long, 16 inch wide walnut slab to be used as an serving/eating bar in a friend’s kitchen. She wants me to retain the cavity area and fill it with a clear resin. The cavity has a partial bottom so I would need to create a temporary dam on the underside until the resin hardens. I have never done this and have lots of questions.

First thing is what are some recommendations for filling this void with something clear. Are there epoxy kits manufactured just for things like this? What finishes are , or are not, compatible? I wonder if the stuff I routinely use (General Finishes Arm-R—Seal, or Waterlox) may cause “fogging” when applied over clear filler. (I plan to contact the finish manufacturers for compatibility questions once I determine what I’ll use for the filler but I wonder if anyone out there has had any success or failures trying this).

Can these fillers be sanded without leaving scratches on the surface? (I have decent sanders and a wide selection of papers). Do the fillers always adhere to the wood or can they separate due to humidity induced wood movement? The slab was kiln dried but is residing in an uncontrolled environment (lumber dealer) right now. At my house it will also be at ambient humidity but my friend’s house will be air-conditioned.
All suggestions are welcome and if you have any pictures of your projects with filled cavities I would be glad if you could post them or send me PM.
Thanks, Marc

-- Windsurfing, Woodworking, Weaving, and Woodducks. "Most woodworkers are usually boring holes"

7 replies so far

View BurlyBob's profile


5936 posts in 2439 days

#1 posted 05-08-2016 03:54 AM

I did exactly what your talking about with a clear resin kit and it came out just fine. Check out Jamestown Distributors. They sell a lot of stuff for boat builders and I know they have what your looking for.

View RobS888's profile


2502 posts in 2019 days

#2 posted 05-08-2016 04:06 AM

Clear epoxy and arm-r-seal are fine together. I use tinted west systems epoxy. It is great stuff, but it has a pretty high initial purchase price for a single use. You can use tape on the backside to keep the epoxy from leaking out. I use one of those sample credit cards you get in the mail to flatten the tape down to the wood or the epoxy will find a way out. Use tape on the top side as a dam to get the epoxy a little proud of the surface and sand or plane down.

This is 3 coats of arm-r-seal over some epoxy filled cracks

-- I always suspected many gun nuts were afraid of something, just never thought popcorn was on the list.

View TinWhiskers's profile


179 posts in 1126 days

#3 posted 05-08-2016 11:16 AM

I had good luck using the spray foam insulation to seal leak thru cavities. Spray from the bottom side.

Large amounts of epoxy will create heat. A void that large could foam up like a volcano if poured all at once.

Random orbital sander with 220 grit.

Use torch to remove bubbles. View on You Tube.

Fill void with glass, marbles, stones…?

View rhett's profile


742 posts in 3841 days

#4 posted 05-08-2016 12:15 PM

I have found clear packaging tape to be the best resource for sealing the bottom of large voids, cracks and knots. I put it on and get a good seal with a J roller. Exceed the sides of the void by atleast an inch. Haven’t had a leak since switching over.

For really large voids, I back up the tape with a piece of 1/4” plywood.

Glazecoat bar top epoxy is a very cost effective 2-part system for filling really large areas with resin.

Pour in stages and mind the bubbles with a heat gun or torch as suggested above.

Have fun and enjoy the experience!

-- Doubt kills more dreams than failure.

View Nubsnstubs's profile


1414 posts in 1904 days

#5 posted 05-08-2016 02:15 PM

Marc, if your going to go with clear epoxy, ask your friend if she would like something in the void to enhance it like a scorpion, spent bullet, broken saw piece, a rock or any number of things that would stimulate conversation when noticed. I did that to a Mesquite table back in the early ‘80’s. I can’t remember the epoxy used as old age is creeping up and exposing my CRS symptoms. I do remember that after sanding to 220, I sprayed sanding sealer and three coats of lacquer and it held up until 2005 when I remodeled the 5’ long table into an 8’ table due to a growing family. The scorpion is still in the table. ............... Jerry (in Tucson)

-- Jerry (in Tucson)

View marc_rosen's profile


143 posts in 3355 days

#6 posted 05-15-2016 01:49 AM

Hey Guys,
Thanks very much for your suggestions. The clear packing tape and heat source comments sound very helpful. My friend does want to “see” though the cavity and she even thought a realistic fake mouse would be fun to see since she is having a wedge shape utility chase painted to look like a wedge of cheese.

Changing the subject here, I recall someone in a different post comment on not seeing the need for a riving knife on a circular saw. I did not see any follow-up to that and can’t find that post but I would add that it appears necessary if you are using a set of parallel cutoff guides like the type that Festool sells. Since the cutoff can’t escape the blade and the remainder stock is captive underneath its track, the saw needs something to help keep the kerf open.

Also, so as to not prolong my other post about clicking on links; Thanks to everyone for their varied but useful suggestions. Marc

-- Windsurfing, Woodworking, Weaving, and Woodducks. "Most woodworkers are usually boring holes"

View Kelly's profile


2103 posts in 3118 days

#7 posted 05-15-2016 11:50 AM

I used to buy my two part epoxy in five gallon buckets for A and B. Battling bubbles was always a problem, but, as mentioned, fanning a torch over the mix removed them. Of course, move fast so you don’t kill the pour.

After a few pours, I started sealing the wood before I poured. That could be poly, glue, lacquer, shellac or anything that would seal the wood and stop air from transferring from it to the just poured resin. Sealing made a night and day difference in the bubble battle.

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