[Public-List] varnish

[edward schroeder]

Having tried, unsucessfully, to use a hard (read "brittle") polyurethane varnish coating on flexible wood, I would be very sceptical of using a brittle epoxy. I would be even more sceptical on a flexible surface such as the main hatch where one stands and shifts their weight while stowing the mainsail.
   
  Epoxies usually are vapor-resistant which means that they do not allow for the passage of water, as a vapor, from passing thru. If one would get a water leak UNDER the epoxy, the vapor might not be able to get out thru the epoxy coating. The result would be "creeping crud" or the progression of adhesion loss.
   
  Architects learned long ago not to place epoxy coatings on concrete floors that were on the ground, as water vapor intrusion lifted the epoxy coating in large sheets.
   
  Ed Schroeder #303 Emotional Rescue (also an architect)

FINNUS505 at aol.com wrote:
  
In a message dated 5/5/2008 7:47:34 A.M. Eastern Daylight Time, 
laughing_gull at verizon.net writes:

have not tried putting the epoxy under it. Does that allow for the wood to 
breath enough? traditional varnish actually breathes a bit, and this was one 
of the gripes about the Bristol Finish type varnishes - that it eventually 
some water got under it, and caused blistering.


That is an interesting consideration. I thought the idea of the epoxy was to 
seal the wood, so that no water could penetrate the porous varnish surface, 
and so that was why a varnished finish protected that way would last longer 
than just plain varnish.

The reason I had to do wood down and redo my main hatch was that the 
varnish was blistering in a few spots. The blisters were not pierced; they were 
small areas where the varnish had lifted off the wood. That is precisely what I 
am trying to avoid with this new system. Ggeeeeeeezzzzzzzzzzz! :)

Lee 
Stargazer #255



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