My son wants to make a slab coffee table. Dadof course has some slabs that are dry enough to serve the need. Of the suitable ones one elm has a punky roughly 3 inch knot, and a Mulberry that has a small punky streak in it on one end. My plan is to prep them and use tung oil as a base coat then use a penetrating epoxy the bad spots.(brand escapes me at the moment) then spar urethane the top, unless they want to pour the top. Will the penetrating epoxy and Tung oil cause issues against each other, epoxy the bad spots first then oil or vice versa. Not sure how you would proceed. I assume the expoxy won't penetrate the rot as well if I get tung oil on it first. Experimenting with a new toy is all.
I'd fill the ugly spots with epoxy before I did the tung oil. It seems riskier to put the oil on first and then have possible adhesion issues with epoxy.
Alan
I have done this a bunch of times but not with the thin penetrating epoxy, just the regular 2 part stuff. Here's is what has worked for me so far:
1) clean all the loose junk out as far as you want to go, wire brush if needed and hit the cracks and crevices with compressed air to clean them out.
2) Tape the far side (bottom) to prevent run through on the bigger cracks. One big through cracks I sometimes tape it with a few layers then screw a strap on the bottom to make sure it doesn't blow out.
3) do your pour to hit all the bad spots, try to overfill them a bit so they mound up. you can also use a chip brush to push the epoxy into cracks or punky wood, I use a tooth pick to poke out the air bubbles in small bug holes, etc. When finished, wipe across it with a torch to draw out and pop all the bubbles.
4) Let it cure.
5) sand it with leveling belts (36 or 80 grit) to get the epoxy down to the wood level, at this point you can bleed (feather) those blend lines in so you only have epoxy in the actual defects.
6) Inspect: if you don't like the results, find some new defects, want to do the other side, or have low spots, repeat steps 1-3.
7) Sand for effect. Get the finish and flatness you want.
8 ) Apply your oil (tung, danish, sae30, whatever). Let that dry and soak in! Do as many coats as you want.
9) apply your urethane. I start with the bottom and sides and do the top last. Many times I have to sand out minor defects and do it again in some spots. Sanding with 320 between coats is recommended provided it is at near full cure (24 hours).
I hope this is helpful.
Quote from: Old Greenhorn on May 15, 2020, 01:56:41 PM5) sand it with leveling belts (36 or 80 grit) to get the epoxy down to the wood level,
Another option to save some sanding time is to use a good scraper or chisel to remove the majority of the excess epoxy. If you catch it in the "green" state it's super easy to shave and saves making a lot of dust.
Alan
I have used the Total Boat penetrating epoxy with good results. In my case, I was using it as a grain filler/surface hardener for some red oak coffee tables that I anticipated heavy abuse from the client (based on looking at the ones they were replacing). I would definitely use the epoxy prior to any other oil/finish, I would think there would be adhesion issues if not. After you sand down the epoxy, which based on my experience doesn't take much with penetrating epoxy,you just finish over it like normal.
Alan and OGH, thanks for the replies I am just unsure and don't want to mess it up, and I hadn't thought about bolstering my tape job with some screwed backing on the bottom that makes sense, just make sure I don't epoxy it to the project as well.
DWyatt, the product I bought was Abatron liquid wood so I bet it's very similar, I have grand hopes of getting to the pouring stage on a couple things this weekend. I've got a new router sled built to run on my mill rails I want to try out. I hope to do it this evening if the day works out. Have to haul the generator out by the mill to make it go, but I am on call this evening and work tomorrow so it's only by luck it will happen. My son's slab will be the second piece I flatten on it (first one wiil be a practice sacrifial bench slab piece).
I have used a lot of West system on projects. It's expensive but it last. I have used there 207 for outside projects or anything that has a chance for UV to to take it's toll on it. I just bought some Total Boat products to test I keep hearing good results about it.
I would do some test before you attempt. Not sure about putting epoxy over oil. Epoxy will change the color. Personally I like the epoxy look
I'd be more apt to try to remove the punky stuff and and epoxy fill, not penetrating epoxy. When doing a fill you can tint the epoxy a transparent color or do a solid or metallics etc.
If I had an ant nest, I might use the penetrating epoxy before doing an epoxy pour to help seal the surfaces and reduce bubbles. I have also used penetrating epoxy on bark to soak it in so it adheres to the base wood. so the bark stays in place. This was on some barnwood that was 100+ years old and thoroughly dry and I didn't want the bark on the wane coming off.
I used Smith's Brand penetrating epoxy (http://www.smithandcompany.org/).
Sealing live edge surfaces and prefilling some defects can be a good idea before doing a big epoxy pour. Less to go wrong.
Also, use a good quality seaming tape to seal the back of whatever your filling. It's worth the expensive cost of the tape. I bought some of the Shurtape brand and I find that anywhere the epoxy touches the tape, it pulls the adhesive off when you peel the tape up. I then have to use 3M adhesive remover to get the adhesive off. I've not been able to get an answer as to whether other brands like 3M 8087 doing that too or not? I'm going to get some of the 3M to try though.
I've used abatron on a log home restoration job to consolidate a 2nd floor windowsill log that would have been a bear to replace, it also supported the porch roof. I used their abosolv to thin it to a very thin consistency for the first few pours to consolidate the deep punk. I'd just consolidate and fill what nature provided.
DonP yes I knew I recognized the product name when I saw it, I think you mentioned using it in a post.
Brad, thanks for the input on the ants nest, I have some dry Green Ash slabs that have an ants nest in them it has the caverns and curly q's in it from their work, a couple inches wide or so. I was thinking it would make an interesting coffee table..... I think a few strategically placed gassed ants would look kinda neat in an epoxy fill. Slightly morbid maybe :o...still fun..Now to get it done..
when ever I have epoxy questions I find the best place to look is the west systems web site.
These guys have seen it all and are really good at answering questions.
WEST SYSTEM Epoxy - Marine Grade Resins & Hardeners (http://www.westsystem.com)
Tom
mrfu, thank you interesting web site.