Spar vs. Water Based Poly Visually

[Mackenzie Robens]

Hello! I am taking on a project for a friend - finishing some wooden signs for her. The majority of them will be inside, but a few outside. They are live edge boards and discs, all the same species of wood.
My question is: If I use a spar urethane for the outdoor signs with the same sheen (satin) and a water based poly (satin) for the inside, will the finished look be the same? There are quite a few of the inside ones so hoping to spray with water based poly where I can. Thanks!

[John TenEyck]

Very doubtful, if the spar varnish is oil based. It will have a decidedly amber color, while almost all WB products are fairly clear, even the ones marketed as mimicking the look or a traditional varnish (like GF's EnduroVar, TC's EM-2000, and Minwax Oil Modified Poly). Even the WB exterior varnishes like GF's 450 Exterior and TC's EM-9000 are pretty amber colored, so those aren't going to match the interior WB's either.

The only way I see to get the same color inside and out is to use the same exterior rated product for both. As mentioned above, there are exterior rated WB products, so spraying them indoors would work.

John

[Jim Becker]

Oil based finishes typically impart a "warmer" in color temperature...an ambering...because of the oil. Waterborne finishes are typically "colder" in color temperature which indeed would look slighty different if, say, two identical signs were put side by side in the same lighting with one finished in the oil based product and one top coated in the waterborne product. One solution is to use a waterborne product that is made to have more of the look of an oil based finish, such as an oil modified varnish. Another method is to add a tiny bit of amber dye to the waterborne product, testing, of course on scrap, to get to the same look. Do note, however, that the sign that will live outside will change color from UV and oxidation more than the interior sign will. So you can certainly match the two initially, but over time...that match may go away. It's not a major thing, however, as long as they are not next to each other, it should not be overly noticeable.

BTW, pro sign makers often eschew using wood for exterior signs these days. They favor man made materials that are much less prone to weathering and for a wood look, they either faux paint or cut a wood grain in with CNC and then fax paint to give the look of wood. Good quality exterior paint lasts a whole lot longer than any kind of varnish outside.

[Mackenzie Robens]

Hi John,

Thank you very much for the note - have you ever sprayed a spar urethane? I never have just because I've only ever used oil based, but is water based as thick? I know I can thin it with mineral spirits, just curious if it works similarly to WB poly.

Thanks again!

Very doubtful, if the spar varnish is oil based. It will have a decidedly amber color, while almost all WB products are fairly clear, even the ones marketed as mimicking the look or a traditional varnish (like GF's EnduroVar, TC's EM-2000, and Minwax Oil Modified Poly). Even the WB exterior varnishes like GF's 450 Exterior and TC's EM-9000 are pretty amber colored, so those aren't going to match the interior WB's either.

The only way I see to get the same color inside and out is to use the same exterior rated product for both. As mentioned above, there are exterior rated WB products, so spraying them indoors would work.

John

[Jamie Buxton]

Don’t spray the standard oil-based varnish. The overspray will make sticky mess all over your shop. In contrast, sprayed waterborne is drying as it leaves the gun, and is mostly dust by the time is three feet away. The only overspray residue is dry dust.

[Jim Becker]

Spraying oil based finish is a thankless task fraught with the potential for a sticky mess from overspray and the need to clean equipment more frequently because it d r y s s o s l o w ... Can you? Yes. Should you? Not in my opinion and many others,

[John TenEyck]

Hi John,

Thank you very much for the note - have you ever sprayed a spar urethane? I never have just because I've only ever used oil based, but is water based as thick? I know I can thin it with mineral spirits, just curious if it works similarly to WB poly.

Thanks again!

I thought I answered this but it must have gotten lost.

I've never sprayed any OB product, nor would I. No way I'd want to deal with the mess from the overspray.

WB clearcoats are lower viscosity than most OB varnishes. The exterior rated ones are no different. I've sprayed both 450 Exterior and EM-9300. The 450 Exterior sprays like a dream. EM-9300 sprays OK, but does not play well with open pored woods like oak. It wouldn't flow into the pores when I put it on an exterior door I made from white oak. I talked with TC who couldn't resolve the problem. I stripped it off and sprayed it with 450 Exterior w/o issue.

John