West Systems Epoxy w/ 206 hardener clouded after 6 months

Beware of using West Systems epoxy with 206 hardener as a pore filler. What was completely clear after finishing and buffing out has gone cloudy in places after about 6 months. Searching for answers on the internet led me to discover that the 207 hardener is intended for clear coating, and the 205 and 206 are not recommended. Save yourselves some sanding and use the correct hardener, or a different brand of epoxy...

It certainly looks like 207 is what we want. I took this from the Lee Valley site:

"The #207 special coating hardener was developed for coating and fiberglass cloth application where an exceptionally clear, moisture-resistant, natural wood finish is desired. The 105/207 mixture resists clouding in humid conditions and has a low blush formation."

From WS, clouding is formed by trapped moisture. You could switch to the 205 hardener. And apply like you would a spray finish, in non-humid conditions. In fact, I really don't do any gluing either when its raining. Good thing its dry where I am.

I've used the 207, but it takes forever to cure. Working through Starbond right now. . .

I found WEST Systems to be very temperamental to all sorts of conditions. One time it worked a treat. The next time a total failure and needing to be stripped back. I've since switched to an epoxy made in Australia that has been so much easier to use, with consistent flawless results every time.

It sounds like you're on the right track to switch to 207 hardener.
I use West Systems all the time at work and never have any complaints.
The 207 is formulated to slow cure, so one shouldn't be surprised.

207 is also good for bar tops, it levels pretty nicely and you can pass a torch over it to pop any air bubbles.

According to a guy on a boat-building forum, the West Systems representative he talked to said that the 205 and 206 hardeners can absorb moisture even after curing. All three ukes were from the same batch, and there was no sign of any blushing/cloudiness when they were first completed. It took around 6 months for the problem to manifest itself. What a lovely surprise. I think I am done with West Systems as a pore filler. Like Allen said it is too temperamental to get consistent results. I have some Zpoxy finishing resin and I am going to switch to that for now.

I would venture a guess that the cloudiness is where the lacquer is separating from the epoxy as a result of amine blush. I've seen that on a number of guitars and wood boats when the finisher failed to properly wash the surface down before applying the top coat.

Yes, if it sets up much between coats the waxy layer comes out and keeps the next coat from sticking. You can get it off with ammonia and to be sure, follow with light sanding. If the paper clogs, it's likely still got some of the amine on it. Do this between coats and after the final epoxy before varnishing.

I used West System on boatbuilding projects since the 80s, mostly living in California where it worked very well, but now that I live in a rainforest I have been leery of it and only use it in the right weather or indoors.

I'm curious if using it as a filler would affect the response of the wood - are you using it on soundboards?

I haven't used it for ukes, but have a situation where I may have about a gap to fill that will not show and I won't ever want to take apart. I'm thinking of using it for that.

-Vinnie in Juneau