spar penetration

[walnutlvr]

If I dilute 50% spar urethane and 50% mineral spirits will I get a deeper penetration. I am using it on ply and would like to get as much moisture protection as possible. Thanks In advance Lee

[dadiOH]

All you'll get is something that is easier to brush.

[dpb]

And fewer solids left from the same applied volume when the solvent dries.

[Tim W]

Varnish is sometimes diluted for the first coat for better adhesion to porous surfaces. Not really a question of penetration but yes, it probably is good practice but not really for penetration and not exactly to form a moisture barrier.

The last coat is sometimes diluted too, to get a better finish, like dadioh says it is easier to brush out.

tim W

[Lew Hodgett]

All you will get is a mess.

BTW, spar varnish is the wrong choice.

True spar varnish never truly hardens.

What are you trying to protect?

Lew

[Tom Dacon]

This is typical for professional finishers in the wooden boat business, for initial coats. The first coat would be diluted 50% (the pros I know use turpentine, not mineral spirits), and the second coat would be diluted 25%. After that it's full-strength coats for most spar varnishes, except for the Epifanes product which is too thick as-shipped for brushing. For that product they continue to reduce it with a little turps and maybe a splash of Penetrol for better brushing and wet edge retention.

We tend to think that we get better penetration by doing this, and it's probably true for soft woods, but teak - used a lot for exterior woodwork on boats - is so oily that I doubt if it penetrates very much. It does make a nice base for the later coats, though. It would be interesting to do it on a scrap piece and then cross-cut it when it's dried and look at it with a loupe to see if you could actually identify any visible penetration.

If you're counting coats, we count the first two thinned coats as just one.

Tom Dacon

[walnutlvr]

[Lew Hodgett]

Since this is in an RV, I'd use 1/4 A/C ply with all surfaces, including edges, sealed with 2-3 coats of laminating epoxy.

(Doubt anybody stocks anything but A/C in 1/4)

Since this is inside away from the sun the epoxy won't be exposed to the sun's UV rays so no need to protect epoxy from sun.

Sand with 100 grit after 48 hours cure time to prep for next coat of resin.

Buy a dozen, 2" chip brushes on sale @ HF, then use one time and throw away.

Costs more to clean them than they are worth which is about $0.25 each.

The RV will be in the dump and those epoxy coated panels will still be in service.

Have fun.

Lew

[dadiOH]

I did (years ago), I couldn't (10x triplet)

[walnutlvr]

Thanks Lew Looks like epoxy it is