|So, it has been an eventful year for the epoxy panel. It has endured everything the New England weather managed to throw at it :) In the summer, it was blasted by pure southern sun for days on end (90º +), it was soaked by acid rain, whipped by dust laden winds and in the winter, it had been encased in solid ice for many days as well as buried under as much as 18" of snow at which time it received no light but was truly tested by freeze and thaw cycles.|
|This is what the panel looked like when it was new and what it looks like now.|
Unvarnished exposed epoxy - Click for enlargement (large files)
Observations & Conclusions
- It seemed from the 6 month sampling that the whitening of the fibers had
stabilized. It seems now that this condition has worsened somewhat on all
the patches but I would say that the change is the worst on the less viscous
epoxies, namely MAS and Raka as well as WS207. It is clear that the epoxy
shrinkage caused the fibers near the surface (covered by thinner layer of
epoxy than the surrounding) to telegraph through and those fibers were affected
Now, the fabric whitening
of the varnished, exposed patches (one goal of this test) rank as follows:
It is quite clear from
the test that varnish reduces 'whitening' significantly but it doesn't prevent
it in all cases. It is also reasonable to assume that varnish effectiveness
is not only confined to UV blocking but to its moisture and chemical resistance
Color (hue) changes
Gloss and Oxidation
(microscopic chemical erosion of the surface layer)- These two
go hand in hand. The more a surface is oxidized the less glossy it is.
Resistance to oxidation was one of the objectives of the test and the
table below ranks the epoxy brands by "glossiness".
West System unconditionally wins the "no varnish - gloss" test closely followed by Raka. WS207 shows no oxidation at all. West System claims their 207 formulation contains UV blockers and it shows. As a note of interest, when I cleaned the remnants of the duct tape with lacquer thinner, the varnish stayed completely inert, however, the oxidized epoxy surfaces dissolved into sticky sludge. It would appear that once that epoxy degrades to some degree, its chemical resistance to organic solvents (like lacquer thinner) declines rapidly.
All varnished portions of the panel maintained the same degree of gloss.
and overall condition of varnished epoxy - The holly grail of the test.
Just to refresh the mind after so much verbiage, the objective was: Which
epoxy will discolor the least and maintain the best clarity.
Protecting your wooden boat - Despite the good results from the "Clarity
test", I say it is still a good idea to cover your hull with some light
proof material. Make absolutely sure to allow the epoxy and varnish (or
any coating) to cure to perfection before you slap a sheet of suffocating
plastic over it. Give your new coatings at least a month to dry and harden.
Protecting the hull in such a manner that permits some air circulation is
very beneficial. If you have done your epoxy work properly (especially the
wetout and thick filler coats) there is little to worry about.
Temperature changes have little effect but light degradation is a fact of life with epoxies and UV resistant coating is indispensable. The choices for clear coat are few; there is varnish, polyurethane, sprayed automotive clearcoat and the newer two part polyurethanes. The polyurethane builds up faster, has a superb gloss and abrasion resistance but at this point you might as well adorn your boat with gold leaf - it's that expensive! ($50-60 per 1.33quart). It gets worse still, once you mix up your two part batch, you either use it or lose it - there is no pouring it back into the can like paint or varnish. So, is it all worth it? Check out the gloss and some of my findings with the two part polyurethane.
And the test goes on! Now, that the degradation of the epoxy has set in, it will accelerate and the differences between the brands will only accentuate. More stuff to follow...keep tuned :)
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Last page update: 11 January 2020