Surface contamination? Did the epoxy cure to full hardness?

Hi Yeller,

the 2nd application after the >5hours of the 1st application it wasn't thoroughly cured of course, but we also had the problem at the seat and the hull after sanding cured epoxy. The surface had been dust free, at least thats what we think.

Regards,

Reinhard

Rather than dust, I was thinking of the possibility of fine airborne oily droplets that might have settled on the surface. Any possibility of that? Otherwise, I'm not sure.

Since you're not getting much helpful input here on this one Reinhard, I'd suggest consulting the epoxy manufacturer, or CLC's customer service. Good luck!

Old Yeller

Hello Old Yeller,

thanks for your attempts to solve this problem. Meanwhile it happened again and I have written to CLC. I already had contacted Fyne Boats who supplied us with the kit and the epoxy. The epoxy itself is for rather low temperatures and slow curing. It works well and sticks like hell even where it shouldn't. 

Fyne Boats could not give much advice. Possibilities are: not properly curing, sanding, cleaning with alcohol, too thickly applied,  viscosity or even amin blush.

The problem now has occured at different occasions. Certainly last time it was properly cured, meticulously sanded and dust free. We even used a squegee to apply it very thinly. It seemed alright in the beginning but appeared again.

Wonder if the workshop temperature is the cause. We have now 22°C and a humidity of > 80% rel. We keep the epoxy in a warmer place so it does not get warmer after mixing it but raher colder while curing.

I will let you know what CLC has to say.

Regards,

Reinhard

Hi Reinhard,

Sorry you're having so much trouble with this. I think epoxy hardener intended for use in low temperatures is normally fast curing, not slow, so I'm a little confused. But if you're using fast hardener in a warm workshop, and are pre-warming the epoxy even more, it seems possible that your epoxy is already starting to gel as it's being applied. Did it feel at all as if it was getting slightly gummy?

I had thought about amine blush being a possibility too, but that seemed unlikely because you had recoated after only 5 hours. But fast hardeners (meant for low temperatures) are more likely to blush, and that might have happened more quickly than usual because of the warm temperatures. Just another possibility ...

Old Yeller 

Orange peel finishes, as opposed to fish eyes, are usually caused by coats being so thick that surface tension overcomes the viscosity. If the layer is thin, then you have insufficient viscosity. Low temperature hardener being stored warm and used in hot temperatures can have this problem because it already starts curing before it's applied. Try cooling the epoxy & resin too 60F before mixing them. Good luck, Laszlo

"Orange peel finishes, as opposed to fish eyes, are usually caused by coats being so thick that surface tension overcomes the viscosity. If the layer is thin, then you have insufficient viscosity."

I need a translation for that Laszlo. "Thick" and "thin", as in the depth of the coating, or in the fluid's viscosity? "Insufficient viscosity" meaning too watery (low viscosity), or too gummy (high viscosity)?

"Low temperature hardener being stored warm and used in hot temperatures can have this problem because it already starts curing before it's applied."

That's what I said, so I tend to agree ...

"Try cooling the epoxy & resin too 60F before mixing them."

That's right. I do think that is the solution to the problem.

Old Yeller 

I saw that Fyne Boats is on the other side of the pond, and the Epoxy is different than what is supplied here.  I would contact the Epoxy tech people, and discuss it with them, that would be the best source of information.  Looking at the picture again, it almost looks like too thick a coat with a batch that was starting to "kick" (harden).  

Reinhard, if you are using fast hardener in warm temperatures and are coating large surfaces, I would actually pre-cool the resin and hardener to 50 degF = 10 degC. Another thing that will help is to mix and quickly apply a series of small batches. Epoxy generates heat as it cures, which makes it cure even faster, so get the epoxy out of the mixing container quickly into a shallow container where it can spread out in a thin layer with lots of surface area to dissipate that heat. In very hot weather, a pan of ice water can be handy to keep the working batch cool.

You might also consider buying some slow hardener. That will give you more working time in warm temperatures, and can usually be mixed with fast hardener for a customized cure rate, for the working conditions that you have.

Old Yeller