Alaska Latex Paint and Varnish Test

[neilm]

Last year I was curious about how good Latex House Paint and Varnish from Home Depot are. So I painted two pieces of AC plywood. One with Behr Latex House Paint and the other with Behr Marine Spar Varnish. I applied one layer to each. I also used one coat of primer under the paint. I then tied these to a stump just below the high tide mark in Prince William Sound on a South facing beach. The Winters are pretty harsh up here so I thought it would be a good test. It's been about 11 or 12 months now and here's what it looks like.

The results suprised me. The varnish did very well only pealing in a couple places but the paint had some serious problems with peeling. Now I'm wondering if I applied the paint correctly. I did no prep work. At any rate I think the Behr Spar Varnish is good enough for interior boats that are not stored in direct sunlight.

http://neilmoomey.com/boats/IMG_1489_Paint_Varnish_Test_700.JPG

[Nanoose]

Others have also talked about the Behr varnish. Dave used it on all the spars this winter (sanded down to bare wood, then built up 10 coats) and we are planning on using it on the new mast as well.

[Wild Wassa]

It is the primer that fails firstly, causing the top coat to then fail with acrylic based paints.

The better quality exterior acrylics do not need a primer as the foundation coat. Primers are now incorporated in the quality acrylic paints during the manufacture of the paint because there is a tendency for non primed acrylic paints, painted on timber, to form mould under the paint when not primed.

Have you got time to do another test? ... without applying the primer that you used. If your timber is clean and the coating uniform and apply a minimum of two coats, the result will be better.

An excellent extreme test, very interesting to see neilm ... for an underpainted coating.

Warren.

[RonW]

If you decide to do another test, add a 3rd. piece of plywood painted with a oil based paint. Instead of a water based or thick house paint that lays on top of the wood, rather then sinking in it and getting a bite.
In your picture you can see how thick the house paint is.

If you are going to build a plywood boat and then cover it with epoxy, you are painting epoxy, and not wood.
That is a different test and requirement for paint.

[Bruce Hooke]

It does seem to me the tests would be more meaningful if you applied the recommended number of coats of paint or varnish...