Finish over epoxy filling questions.

alan gage · February 17, 2020, 10:06:43 AM

Epoxy plays much nicer with foam than vinylester resin.

I've used epoxy extensively with XPS (typical blue or pink builders foam) and can't remember if I've used it with EPS (white) foam or not. I do know that I've melted EPS foam with vinylester resin. I've also eaten through plastic mixing cups with vinylester that were fine with epoxy.

I've also had epoxy cause foam rollers to fall apart (while other brands were fine). I think it was the adhesive holding the foam to the cardboard roller that actually failed. Epoxy will slowly cause foam brushes to swell, but usually not until you're done with them unless it's a big project. Some epoxies are worse in this regard than others.

For mixing epoxy I use empty yogurt cups or clear disposable plasitc cups (like you'd buy for a picnic).

Alan

Weekend_Sawyer · February 17, 2020, 12:10:34 PM

I have had good luck with FamoWood 2 part epoxy. I get it from Lowes or Amazon. It flows into cracks very well, and doesn't have excessive bubbles. One thing I learned was that I was stirring too hard and causing lots of bubbles. Now I stir about 1 rotation per second. I use plastic party cups. Spar poly works well as a top coat. I've been playing with die latley so far so good!

Weekend_Sawyer · February 17, 2020, 12:21:45 PM

Here's a pice of walnut that was pretty rotted, then I dropped and broke it in half.
I taped it up and flowed epoxy with blue die in it. after it sat for a few minutes I sworled it with a popcicle stick. Top coat with gloss spar poly.

I used this for my mounts this year.

I have had good results using the blue painters tape to seal the wood to keep it from flowing through. I do put some cardboard under it as I have had some seeps.

My next thing to learn is to try making a mold using house wrap tape and 3 mil plastic.
Jon

doc henderson · February 17, 2020, 12:36:37 PM

the area where the tape goes needs to be smooth and dust free for any tape to do well. I find that tape degrades over time, but the frog tape in a reusable plastic container keeps the longest.

Nebraska · February 17, 2020, 02:01:53 PM

Red Solo cups, one for me one for thee e-pox-eee..... :D probably not a good thing to combine. I would be committing a PUI. (Sorry can't help the bad Dad Jokes).

Dying the epoxy will be on the list eventually, work is busy it's taken me all morning to get thi s reply written.

Those same plastic cups we use them for mixing methyl acylic adhesive for putting wooden blocks on cattle with toe injuries. Take the pressure off one side of the foot helps reduce the pain and let the injury heal. Happier cow. Nothing to do with this subject just an fyi....
For the volume I was using I just borrowed a few little plastic snap lid condiment containers from my buddies minimart. Seemed to work well and you could pinch them to pour on bigger projects than mine. Easy to find.

Old Greenhorn- sorry repotting old heat chucks, I didn't quite follow enough to visualize the process. You used high temp Devcon epoxy to fill a worn cavity, cover it with heavy mill plastic. (Would one use the heavy drop cloth plastic, silage tarp material, or contractor cleanup trash bags to cover big pours? I have all three varieties .... thinking ahead. ... Then it was machined back to spec. The only weight was the aluminum sheet just to keep the plastic and epoxy flat.

Ian- ok no plastic flowers, or at least do a compatability test first.
Weekend_Sawyer that's a really cool project.

doc henderson · February 17, 2020, 02:20:48 PM

i have used an epoxy marketed for dry rot and it is thin like water. Pour it into wood that is spongy like Styrofoam and it makes a hard chunk. used it on the transom of my O'Day Javelin back in the 90s.

alan gage · February 17, 2020, 02:36:22 PM

One thing I rarely see mentioned about putting a finish over epoxy is that the epoxy needs to be fully cured and any amine blush removed, otherwise the finish can remain a sticky mess for days. Sometimes it will eventually get hard and other times you need to scrape/sand/melt it off.

Some epoxies are more prone to amine blush than others and certain conditions (temp/humidity) can make it more prone. It can be removed with soap, water, and sanding.

As far as fully cured epoxy it also depends on what you're using for resin/hardener and the ambient temp. Just because it's hard to the touch doesn't mean it's fully cured. The worst problem I have ever had with this was using an epoxy that was made to cure at temps of 85+ degrees. This was winter and I usually bring the shop up to 65-70 degrees for epoxy work. Nothing in the info sheet about that and I didn't realize what was going on until I was digging around and found it mentioned in the description on a vendor's website. I'd used it to fiberglass the outside of a canoe and it wasn't fully curing. I built a frame around the canoe, covered it in plastic, and put space heaters underneath to get the temp up to 90+ degrees. But the fact that it was in a partially cured state for a few days seemed to really retard the curing even when proper temps were reached. It sat under that tarp with heaters for 3-4 days until it finally felt hard.

A couple days later, after washing and sanding, I applied varnish and then it wouldn't cure! The problem was still the epoxy underneath. It might have felt hard but it was still curing. Back under the hot sheet and after a few more days I gave up and sanded off the varnish, set the boat aside for a couple more weeks to finish curing, and re-varnished it. Then everything went fine.

Most of the time this isn't an issue. But sometimes it is. It's good to be aware of it.

Alan

Ianab · February 17, 2020, 03:28:59 PM

Yes, cold temp can be a problem. Most epoxies have a minimum temp and time that they need to cure, and that can be up to 24 hours. So although it's warm enough when you pour, the heat goes off at the end of the day and it gets too cold for the chemical reaction to complete. Then it can be a real problem to get it properly cured.

I've "tented" pieces, with a safe little oil column heater under the table, to keep things warm enough overnight to make sure it got it's full time / temp.

Nebraska · February 17, 2020, 11:11:40 PM

Ok- Alan amine blush I don't know what that is. First time I recall seeing it mentioned anywhere. I'm sure I can find it and learn something. I put a coat of tung oil on the little project this evening it didn't look like the epoxy that had seeped along the edges will show. I had roughed it up with a little med sandpaper first. So I'll let it set for a few days and see how it goes.

doc henderson · February 18, 2020, 07:24:47 AM

in addition to full cure of the epoxy, the tung oil often requires 72 hours of cure (penetrating oil finish) before urethan (top coat) can be applied. a warm environment will help.

Ruffgear · February 18, 2020, 08:12:12 AM

Lots of good info here. I'll add a couple things. Waterbased poly works good over epoxy, just make sure it has something to bite into. Most new epoxies claim to have no blushing. Chill, eco, mas, just to name a few. I've also used just pure Tung oil, I love the look and worry about longevity

alan gage · February 18, 2020, 10:56:30 AM

Quote from: Nebraska on February 17, 2020, 11:11:40 PMOk- Alan amine blush I don't know what that is

Like Ruffgear said most epoxies anymore are pretty much blush free. I've only gotten it a handful of times. I know some people who are anal about it and water/soap wash every surface after applying epoxy. Most others are like me and ignore it if it's not obviously there and get bit in the butt now and again.

A little article that explains it better than me: Amine blush when working with epoxy: what you need to know

Alan

Nebraska · February 18, 2020, 11:13:34 AM

Thank you Alan.

I set the piece in the garage overnight, my wife made a comment about smelling it. College aged daughter popped in as I was finishing the coat and said what's that dad it smells good. She also said it looked good too. (That's my girl ;)) She wants to refinish a bus and live in it but that is another story. ???
It's back inside on the table again warmest spot in the house. Won't get touched til Sunday too much work and end of season high school sports to watch for a few days.

olcowhand · April 10, 2020, 04:08:00 PM

Nebraska,
So how did it turn out? I need to fill some knotholes and voids, then finish with Poly. I'm curious.
Great thread, everyone!
Steve

gspren · April 17, 2020, 09:26:52 AM

I am currently drying some red oak cookies 26"D x3"T to make some end/coffee tables. I'm not a furniture type wood worker and these won't go in the house, more like man cave or garage quality. After about a month setting on edge in the barn leaning against a wall the cracks are getting big so the epoxy will come into play. Can you just fill the bottom side with wood putty to stop the epoxy? Setting in a dry barn, upper level with wooden floor, how long should the cookies dry? Should I now treat them with anything to kill bugs? More questions later.

doc henderson · April 17, 2020, 09:36:33 AM

If you use clear epoxy, you may see through to the bottom. to use less epoxy you can seal the bottom then fill with whatever, coins, bullets, marbles, rocks, wood shavings, coffee grounds. it has a min. cure temp but the barn should be ok. you can also put color in the epoxy. lots of video out there for ideas. the old bondo is an epoxy based filler. many fillers with crack and need several applications. if you tape and seal the bottom, you can start with some thinner pours (1/4 inch thick) to seal up the bottom.

farmfromkansas · April 18, 2020, 10:36:30 AM

Used to be this liquid that would set up when you added hardener called "polyester resin". Now I see the same stuff sold as fiberglass resin. Walmart sold it by the gallon. Is that the same product? Saw a table top made from a rotted log, guy cut a top for a coffee table out of it, and did not touch the rotted wood, just started coating it with polyester resin, and must have been 1 1/2" thick in the center, perfectly clear, coated with gloss lacquer. Beautiful top.

doc henderson · April 18, 2020, 09:07:05 PM

the bondo wal-mart resin can tend to have a green tint. Hobby Lobby has a glaze coat casting resin. this is fine to fill a hole. if I were doing a river table, I would go with a more industrial product. West marine and such. @tule peak timber is leaps ahead of most of us when it comes to using these chemicals, in terms of product pros and cons. i think he buys it in 55 gallon drums. 8) :D

alan gage · April 19, 2020, 08:49:56 PM

Quote from: farmfromkansas on April 18, 2020, 10:36:30 AM
Used to be this liquid that would set up when you added hardener called "polyester resin". Now I see the same stuff sold as fiberglass resin. Walmart sold it by the gallon. Is that the same product? Saw a table top made from a rotted log, guy cut a top for a coffee table out of it, and did not touch the rotted wood, just started coating it with polyester resin, and must have been 1 1/2" thick in the center, perfectly clear, coated with gloss lacquer. Beautiful top.

Biggest difference between polyester/vinylester resin as opposed it epoxy is that the ester resins use MEKP as a catalyst. Put in more MEKP and they cure faster. Put in less MEKP and they cure slower.
With epoxy there is a dedicated ratio of resin to hardener. Putting in more or less hardener doesn't change the setup time. Well, actually I guess it does because if you don't get the ratio fairly close it might not setup at all. To change the cure time you use a different hardener. Some set up slow, some fast. I usually buy a fast setting hardener and a slow setting hardener and mix them together if I want a medium set time.
Also epoxy doesn't stink like the ester resins do. Epoxy is thicker too. Sometimes this is good and sometimes not.
Not many people make the switch to epoxy and go back to the ester resins. I use vinylester for things like infusing small parts when I want something really thin that flows well but mostly it's epoxy for me.
Alan

Nebraska · April 20, 2020, 10:26:27 PM

@olcowhand

It was the bottle opener on the wall. I don't have a closer up picture of it installed in my son's apartment, we quick built the desk top In the backround so they could work from home.. I didn't see your query until this evening. I think it turned out ok, I can see the things I wasn't happy about but unless you know them I don't think an average glance would see it. It was approved by his significant other so if she thought it was ok, I'm good.