Replies

1. 
   SteveSchoene | Oct 14, 2006 12:03am | #1

   Yes, there is a better way.  The glass should give you a chance of having a clear finish work, but two coats of poly isn't going to do it on the exterior.  You should use a good marine spar varnish, since it will handle the UV that does come through the glass much, much, much better than semi-gloss epoxy.  There are three brands:  Interlux Schooner, Pettitt Captain's, and Epifanes Gloss.  Yes, they cost $25 per quart, but it is worth it.  And more coats is better than fewer.  Six coats is the standard.  (It's not about rain and snow, its 95% UV light that damages the finish.) 

1. 
   doorboy | Oct 14, 2006 12:44am | #2

   I agree with Steve completely, although I will add that it's probable that the glass storm door is adding to the problem with the buildup of heat that's likely in the space between the door and the storm door.
   If it is, like you say, "protected from the elements", then you may not even need the storm door."Kinky for Gov. of Texas"

2. 
   Dreamer | Oct 14, 2006 02:28am | #3

   Thank you for your quick reply.  So I can get it right, you recommended a marine spar varnish.  Is a spar varnish the same as a spar urethane? 

   Dreamer

1. 
   SteveSchoene | Oct 14, 2006 03:06am | #4

   No.  Good marine spar varnish does not contain polyurethane.  Until you start getting into the two-part polyurethanes ($60 per quart and some seriously nasty solvents) urethane resin is more susceptible to UV light than the phenolic or straight alkyd resins in the marine spar varnishes.  You will only find the good marine spar in a marine supplies store, never in a "big box", and only in a few ordinary paint stores in boat crazy towns like Annapolis.  A good mail order source is at http://www.defender.com  they carry all three decent varieties. 

   Is a tough call--heat versus UV.  I'll guess that the UV would do more damage than the heat, but I wouldn't bet too much.  At least don't go for a really dark stain--that will exacerbate the problem.  The marine spar is very flexible so it's probably the best solution for heat too. 

   The most durable finish for wood doors is a really good enamel in a light color. 

    

1. 
   Dreamer | Oct 14, 2006 04:11am | #5

   You've been a great help.  Your responses were timely and informed.

   Thank you.

2. 
   IdahoDon | Oct 14, 2006 05:12am | #6

   Steve is right, use a spar varnish.  The formulations are all different and it is better to error on the better side for a long-lasting finish on an exterior door.  Essentially the spar varnishes use a formula that remains more flexible and survives extream temp variations without developing the small cracks common with normal polyurethane that allows water to work its way in.

   I'd also add System 3 spar varnish as a good alternative.  Woodcraft usually carries it @ $35/quart or so.

   Another option is one of the high-grade spar varnishes sold for aviation use.  Check out http://www.aircraftspruce.com or http://www.wicksaircraft.com .  The most durable I've heard of are the two-part formulas, that aren't neccessarily more expensive than a really good one-part spar, but do require more attention to the application.

   An aviation grade clear two-part polyurethane is durable and survives well on all surfaces, but is quite spendy and not at all like what carpenters normally think of as a polyurethane.  It's similar to a clear automotive paint with more flex and strength.

    

1. 
   Dreamer | Oct 14, 2006 02:40pm | #7

   Thank you for your reply to my query. The three responses to my query are guidance I needed for my project.