Fiberglass Problems

Dave Osborn

I’ve glassed the hull of a strip built 1940ish Rhinelander rowboat. I washed the blush off and sanded it, tacked it, and applied a coat of paint. The paint was fairly recent, the glass and most of the sanding was in February in a warm workshop.
It is now seeping blush through the paint. There are a few reasons that can cause this, but it too late to beat that horse, I need to know how to fix it.
The second photo is what it looks like when I wiped it with thinner. The third photo shows the amber colored blush seeping from under the paint.
Anybody have any suggestions to remedy this?


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I'm no help to you, other then trying alcohol to clean it. (I've used alcohol to thin resin so....?)
but when I researched and started to build my strippers, one of my 1st decisions was to always use non-blushing epoxy.
I was diligent in washing the blush off between coats. The last wash was with Dawn and an abrasive pad on a random orbital sander. Now it’s sweating blush.
Which brand of epoxy did you use?
I almost exclusively use West Systems/Gougeon Brothers.
The 2 published articles* on their website say amine blush is water soluble and can be removed with soap and water, with a liberal scrub using a Scotchbrite pad.
Since this "after the fact" appearance, have you tried wiping with acetone?

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My hunch would be that it is not blush, but residue from the tack rag. My #1 rule for working with epoxy is always to avoid contaminating the surface with other chemicals, and a tack rag can do that and should be avoided. I've worked with WEST Epoxy ever since it became available and we moved away from polyester resins.
Thanks Todd. I was hoping you’d chime in.
I’m going to sand or strip the paint off and start over with the process.
I also noticed that you are getting an awful lot of telegraphing of the cloth weave, which you can see in image #3610. Those tiny whitish specks are too regular to be random. The usual cause of this is sanding down into the cloth due to not enough filler coats. It can also be caused by heat expanding the wood slightly and stretching the fiberglass - something that glass doesn't do very well. I had a stripper double kayak that I built and one summer I hung it up high in the rafters of our garage for storage. It was a really hot summer and what had originally been a smooth outer surface developed areas where the weave was both visible and feel-able. I was not a happy camper.


Those Rhinelander Guide Boats should get more attention. We have a place outside of Rhinelander and once in a while we will see one which was probably restorable before someone turned it into a front yard flower box. There was a guy a few years ago building fiberglass replicas, but I don't know what happened to the project. I wasn't thrilled with the potential lack of durability for the cedar gunwales, keel and skeg, but the glass hull looked decently done.