“Chalky Epoxy”

[PaddleTime]

Hey guys,

Getting the search narrowed down on a new canoe purchase, one consideration is obviously longevity / maintenance / what type of condition the canoe will be in down the line. For older epoxy canoes I see a lot of references to the epoxy taking on a “chalky” characteristic with age. Understood this can be maintained and restored, however prior to that when people say “chalky”, do they mean:

1) A cloudy appearance only (no actual “chalk”)

or

2) Actual epoxy breakdown particles with physical chalky dust on the surfaces of the canoe

Thanks for any insight!

 

[ppine]

Amine blush. You can get rid of it and then varnish for UV protection.

 

[PaddleTime]

Thanks @ppine - I had thought amine blush was released during cure (and I’ve been investigating blush-free epoxy as well) - are you saying the epoxy continues to blush as it ages?

 

[JohnSand]

Epoxy and other resins degrade in sunlight. Old fiberglass boats get chalky looking. Penetrol will brighten them up, there are probably other products too. Painting covers the discoloration and prevents further decay. I wouldn't worry about a finish even if it transferred "chalk" by touch. If rough or crumbly I would avoid it.

 

[Alan Gage]

Bell was widely known for this problem. I've heard explanations but I don't know if any of them are actually accurate.

I had a Magic with the 'issue.' I didn't bother me so I never did anything about it. No problems at all.

When it was time to sell the boat I wiped down the interior with alcohol and coated it with varnish. That took care of it.

Alan

 

[Glenn MacGrady]

I have several composite canoes but I don't think any were made with epoxy resin, but rather various types of vinylester. I have experienced two types of cloudiness or chalkiness, one type on the outside of the hull and the other on the interior of a Bell canoe.

Most composite canoes have a get coated exterior covering the fabric and resin matrix. Any gel coated canoe exposed to UV from the sun for a long time, as from being stored outside, will oxidize into a chalky powder. This is actually a micro-pitting of the gel coat. If it's not too severe, this layer of chalkiness can be polished off. It can also be optically concealed by applications/wipe-offs of Flood Penetrol two or three times a year. If the gel coat is too much oxidized, it will likely have to be painted over.

The type of vinlyester resin used by Bell canoe for certain years will turn into a chemical cloudiness in places where water has pooled on the interior. This cloudiness can easily be removed by wiping with acetone. It will eventually return after more pooled water exposure unless you coat the interior with some sort of protectant. I use Flood Penetrol on the interior for this purpose, too. I suppose varnish would provide long term protection, but I'd be concerned about adding weight with too much varnish.

 

[PaddleTime]

Thanks guys. Right now I seem to be focusing in on skin coat epoxy canoes. Sounds like the epoxy could get powdery with age? Appearance wouldn’t be an issue, but wouldn’t be a fan of dealing with epoxy dust on trips…my understanding is you can become sensitized even to the dust?

Wouldn’t feel great about the micro particles being left in wilderness waters either. At least with maintenance it seems resolvable but I already have more than enough things around to maintain and keep track of. Any other “chalky epoxy” input / experience appreciated.

 

[bark-eater]

Epoxy is sensitive to uv degradation. Polyester is also, which is most obvious with chalky gelcoat. I've got a bunch of semi neglected unfinished epoxy projects that have been sunburned. I've consulted the West Systems techs, and have been told that its best to grind it all off for a 100% repair. I'm not sure that's necessary for canoes, but I would agree for an aircraft. For a Skim coat I would think the primary concern would be cosmetic, so sanding down till it looks good enough and brushing on more epoxy would get you there. The same would work with a polyester skim coat. There are a number of more uv resistant epoxy's available to help break the cycle. A UV resistant polyurethane would work, to encapsulate and protect what's there if you dont need to add bulk to the skim coat. As far as Epoxy sensitivity, the issue as I remember was exposure to uncured resin and or catalyst. Once its fully cured the epoxy is innocuous. The big "No No" is to sand before its fully cured. Depending on you sensitivity, that could be like taking a weed burner to Poison Ivy.

 

[PaddleTime]

Thank you, great info. Any idea if epoxy on a skin coat would be more of a chalk in looks only or are we talking like you ran your finger over a chalkboard type chalk / powder with UV exposure? Curious to know what I’ll be dealing with, with age of the canoe.