Thread: Two pot polyurethane varnish over urethane-alkyd varnish?

Generally you can apply any finish over any finish, assuming compatibility or a good primer to insure it. In clear wood finishes, this is much less true, mostly because you can't use a primer or tie coat.

Traditional alkyd finishes are fairly soft, so they move a bit with temperature and humidity changes. LPU's or WR-LPU's are much harder and thus less flexible, so you'll be applying a relatively hard coating over a soft one. It's likely one will test the others peel strength at some point. The obvious thing to do is a test panel and see what happens. Of course it'll take some time to evaluate the results.

Originally Posted by PAR

Of course it'll take some time to evaluate the results.

ha ha! If only we had access to time machines.

That's very helpful info. Thanks again Paul. I will keep using the urathene-alkye varnish I have, since I have only been coatings parts to protect the epoxy. When I do the inside of the boat, centreboard and rudder I'll use 2 pot for a harder coating. Since I'llbe using leather on the spars, I'll stick with single pot varnish for the mast.

Cheers,
Mark