Sticky Epoxy

[Christian Linder]

Hi everyone! 

Building the Melanesia is turning out to be a bit more complicated than I thought.. since it is the first time I build a boat.

I coated the interior of the pannels with 3 layers of epoxy. I haven't used the West Systems Epoxy but another one I found a bit cheaper.

I might have messed up a bit on the resin-hardener ratio because after 4 days some parts are still a bit sticky... and it is about 25 to 30 degrees celsius (77 to 86 fahrenheit) here in Barcelona these days, so it is not because of low temperatures precisely...

What can I do now?

[Allen Bosely]

I'm not expert here, but from what I've read, you need to scrape all the unhardened epoxy off, wash it down with white vinegar to remove all the unhardened epoxy residue then reapply new epoxy.

Also, don't forget you need to coat all the epoxy that can get any sun exposure with a compatible varnish.
The UV will degrade the epoxy. I'd give it three coats of varnish myself.

The varnish goes on a lot easier and quicker than the coating the surfaces with epoxy.

Be sure to sand all the epoxy surfaces before varnishing.

Different brands of varnish have somewhat times between coats that sanding isn't necessary. But I wouldn't wait till the end of the time listed to recoat without sanding though. Sometimes the mfrs are a bit optimistic son they're time between recoat switch out needing to sand.

By sanding I mean just remove the glossy surface. You want a even dull or satin finish before varnishing and don't miss or skip any spots.
Rinse and dry surface before varnishing.

It doesn't take long to degloss the surface. Your making a 'toothy' surface for the varnish to bond well to.

Cheets, Allen

[Robert Hughes]

It's possible that your epoxy has set ok, and the stickyness is actually amine blush.  This can form with many types of epoxy, where the surface is exposed to the air as it sets.

If it is amine blush it should wash off easily with warm water with a bit of washing up liquid in it.  The surface then needs to be flushed with fresh clean water and allowed to dry.

The mixing ratio does need to be quite accurate with epoxy.  I aim for better than 1%, and use a digital weighing scale I bought on Amazon for about £10.

Good luck, I hope it is only amine blush and you don't have to scrape all the resin off.

[Christian Linder]

Hi guys!

I think I didn't get the ratio right because I mixed by volume although it was by weight. However, I just checked, doing the mix by volume again and weighting it and it's pretty much the same amount by volume as by weight....

Robert, that's interesting. I just tryed wiping it with a cloth wetted in hot water and soap and after rubbing a bit it was coming of just like it was some kind of rubber. So is that amine blush? 

After wiping and rubbing it all of, what should I look for? The surface should be rock hard, right? I shouldn't be able to dig my nail in it, right?

Next time I will mix it with a scale for sure to get it precise.

Thanks!

[Christian Linder]

Another interesting point: I used the same mix of resin and hardener, after coating, to glue some parts by thickening it with microfibres. Now, the epoxy that was mixed with microfibres got rock hard... of course it was not applyed as a fine coat but in bigger amount, I don't know if that has to do also.

[Robert Hughes]

That description of being like some kind of rubber sounds like epoxy that's not fully cured, rather than amine blush.  Amine usually washes off fairly easily, rather like a very thin coat of honey would.  Whatever it is you do need to get back to a hard surface.  The difference in the batch with microfibres is that it's likely to get hotter, but your 25 to 30 degrees should be hot enough for a proper cure anyway unless you've got a resin that needs specially high temperatures.

Christian Linder said:

Hi guys!

I think I didn't get the ratio right because I mixed by volume although it was by weight. However, I just checked, doing the mix by volume again and weighting it and it's pretty much the same amount by volume as by weight....

Robert, that's interesting. I just tryed wiping it with a cloth wetted in hot water and soap and after rubbing a bit it was coming of just like it was some kind of rubber. So is that amine blush? 

After wiping and rubbing it all of, what should I look for? The surface should be rock hard, right? I shouldn't be able to dig my nail in it, right?

Next time I will mix it with a scale for sure to get it precise.

Thanks!