spar urathane over epoxy

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spar urathane over epoxy

Postby yrock87 » Thu Sep 22, 2016 1:03 pm

I am finishing up the finish of my build. I used RAKA UV epoxy over all exterior surfaces and on the galley floor and counter. after about a week, then I covered that with MINWAX Spar Urathane. all is well with the walls.

I got a little ahead of myself as I was using the last of my epoxy on the galley. I had already started urathaning over cured epoxy on the floor, but I needed to add some more expoxy to the rear edge as waterproofing. I inadvertently overlapped some fresh epoxy and fresh urethane over about a 2 inch strip. it appears that it is not curing properly. a week later and I still have a strong smell and a slight tacky feeling at that strip. the rest of the floor (urethane), and the rear edge (epoxy) all cured since then.

so what do I do to clean up this mess that I am guessing will never cure? last night I tried rubbing it down with paint thinner. I will see if that helped tonight after work. if it didn't, what should my next step be?
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Re: spar urathane over epoxy

Postby tony.latham » Thu Sep 22, 2016 5:58 pm

I inadvertently overlapped some fresh epoxy and fresh urethane over about a 2 inch strip.


Let me make sure I understand this. You laid down fresh epoxy and then put a coat of varnish over it, right? (I've done many dumber things BTW.)

Two-bits says the epoxy cures just fine under the varnish. (Note the bet: two bits. That means I don't know for sure but am willing to wager a quarter.)

As far as the varnish, another two-bits says it'll be fine if you expose it to the sun for a day. UV rays will help cure even UV resistant finishes.

But let us know.

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Re: spar urathane over epoxy

Postby Rick Tyler » Thu Sep 22, 2016 6:05 pm

If the epoxy never sets, you know what you will have to do -- you just don't want to think about it. Acetone works pretty well to clean off wet epoxy, but if it doesn't set you are likely to end up scraping and sanding to get it off. It's no fun, but I've been there, too.
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Re: spar urathane over epoxy

Postby Tomterrific » Fri Sep 23, 2016 10:12 am

You could try heat to speed the cure. Sun and maybe a hair dryer.

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Re: spar urathane over epoxy

Postby yrock87 » Fri Sep 23, 2016 12:00 pm

Yup, fresh epoxy with fresh urethane over the top. It is as dumb as it sounds. except that it was accidental... but yes, dumb.

I had heard that urethane can interfere with epoxy curing.

notes from last night. the tackiness is gone. however it is soft enough that my finger nail can mark it easily. however my finger did not have any residue or oder after touching the surface, so that is a plus. I think that the paint thinner got the tacky, nasty uncured urethane off, but the epoxy is still uncured. I will try adding some heat to see if I can encourage the epoxy to set now that there is no urethane on top of it. In addition to being under a coat of urethane, it has not gotten above 68 this week. that didn't stop the rest of the epoxy from setting, but maybe it was the combo of cool temps and urethane that interfered with the curing.

if the hair drier doesn't work, time to get sanding!... at least it is only about 1-2 sqft...
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Re: spar urathane over epoxy

Postby tony.latham » Fri Sep 23, 2016 1:48 pm

if the hair drier doesn't work, time to get sanding!... at least it is only about 1-2 sqft...


Sounds to me that it's setting up.

Sandpaper will quickly fill up with the uncured stuff. Acetone and a paint scraper while gloved up will pull it off quickly.

But give it some time.

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Re: spar urathane over epoxy

Postby KCStudly » Wed Dec 21, 2016 12:32 pm

Yes, give it some time and you might get lucky.... but if you didn't get enough heat from the initial chemical "kick" it may never harden. I had an area like that on my build where I either screwed up the mixture ratio or maybe spread it on too fast and it was too cold to kick. I ended up scraping it down and was glad that I did when I did. While it was still soft-ish it wasn't that hard to remove, and once I was back on track it was business as usual and I kept right on going.

Wasn't that bad just scraping it up.... once I bit the bullet.

When you are pushing close to the manufacturer's recommended working temperatures, one thing you can do to help is once the resin is mixed, let it sit in the cup a little bit before spreading it out. This allows the mass to start to warm up a tad, ensuring that the chemical reaction starts, and the cold temperature buys you a little working time at the other end. In cold weather I always drag my resin and hardener along with me so that it mostly stays at room temperature, then I drag it to the shop for a couple hour session not below 40-45 deg F, then back into the warmth. So long as I feel it start to warm in the cup, even just a little, it works out fine.
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Re: spar urathane over epoxy

Postby Atomic77 » Thu Feb 23, 2017 3:13 pm

My two bits says the chemical reaction was disturbed and it will never be right. Curious about the outcome...
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Re: spar urathane over epoxy

Postby S. Heisley » Thu Feb 23, 2017 10:36 pm

I understand that some epoxy will out-gas while curing. If that happens, plan on cleaning everything off, sanding it a bit and reapplying.
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Re: spar urathane over epoxy

Postby tony.latham » Thu Feb 23, 2017 11:40 pm

S. Heisley wrote:I understand that some epoxy will out-gas while curing. If that happens, plan on cleaning everything off, sanding it a bit and reapplying.


This is an old post from September. He never did tell us if it cured.

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Re: spar urathane over epoxy

Postby yrock87 » Fri Feb 24, 2017 5:39 pm

It did cure. took about two weeks to loose its tack entirely but now it is all fine.

lesson learned, don't get ahead of yourself when working with epoxy
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Re: spar urathane over epoxy

Postby JamesDixonLR » Thu Jun 08, 2017 9:19 am

Question: was the urethane over epoxy to keep UV off the epoxy? In researching my project, I read that epoxy breaks down under UV. At the same time, epoxy has good qualities so maybe you want it and want a way to protect it.
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Re: spar urathane over epoxy

Postby yrock87 » Thu Jun 08, 2017 2:36 pm

JamesDixonLR wrote:Question: was the urethane over epoxy to keep UV off the epoxy? In researching my project, I read that epoxy breaks down under UV. At the same time, epoxy has good qualities so maybe you want it and want a way to protect it.

That was exactly my reasoning. It probably isn't necessary inside the galley since it will be closed more often than not, but I figured extra protection can't hurt.
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Re: spar urathane over epoxy

Postby tony.latham » Thu Jun 08, 2017 3:11 pm

JamesDixonLR wrote:Question: was the urethane over epoxy to keep UV off the epoxy? In researching my project, I read that epoxy breaks down under UV. At the same time, epoxy has good qualities so maybe you want it and want a way to protect it.


I built a cedar strip canoe years ago and that's exactly the way it's done. The spar varnish goes over the epoxy to protect it from UV rays. There are epoxies now with some type of UV resistance but I don't know how effective they are.

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Re: spar urathane over epoxy

Postby Atomic77 » Thu Jun 08, 2017 5:13 pm

There are epoxies today that have very good UV inhibitors built in to stop yellowing of the epoxy on things such as table tops sitting near a window. Even though these supposedly work well, all the literature I've read by the manufacturers say they still do not recommend outdoor use. So sounds like a top coat is still necessary.
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