Exterior clear coat over artist's painting

[ed kerns]

I have a friend who wants a bird feeder to be built of cedar. Easy enough, but he is also looking to have a mural painted on it using artist's water based paints. I'm looking for recommendations for the best clear coat to offer some weather protection, but that will affect the artwork as little as possible. I appreciate all advice!

[fredhargis]

I have nothing to contribute to this question, since I don't know what might fill the bill. But I'm wondering is an automative clear coat product might do what you want. I've never tried to buy or use one, but it would seem to meet the requirements. Might be pretty expensive as well.

[jteneyck]

Make sure your paints are exterior rated to avoid fading.  For clearcoat, automotive clearcoat is the ultimate but as Fred said, expensive.  Another possible option is something like SW's exterior deep paint base (#3 or #4?) with no added pigments.  It goes on milky but dries clear.  They will look at you like you have two heads, but tell them you want it with no pigments.  

John

[fredhargis]

John, is that oil based exterior paint? I'm still looking for one to replace the Olympic i used to be able to get.

[jteneyck]

John, is that oil based exterior paint? I'm still looking for one to replace the Olympic i used to be able to get.

No, Fred, it's the waterbased one.  Someone here several years ago used it on a large cross and the durability was very good; something like 2+ years w/o the need for maintenance.  That's longer than any exterior clearcoat I've used, though I suspect automotive clearcoat would last longer.  

And now I remember which specific paint it was, and I'm pretty sure it's the "Deep Base" one.  

[Willyou]

I too have wondered about using the automotive clear coat. You can get it in spray cans and is not too expensive, but I'm not sure whether that is the same stuff as what is used on a car finish. Clear coats are also designed to be used over metal. I wonder if the expansion and contraction of wood would affect it differently.

A couple of years ago or more, I did a test of using untinted base (oil based) and it failed. It was 3 coats of SW All Surface deep base. I placed the sample board out in the full sun and weather and after a few months the finish had split and cracked and started to flake off. I think I posted a report on it here. I have not tried the same test with water based products.

[jteneyck]

I too have wondered about using the automotive clear coat. You can get it in spray cans and is not too expensive, but I'm not sure whether that is the same stuff as what is used on a car finish. Clear coats are also designed to be used over metal. I wonder if the expansion and contraction of wood would affect it differently.

A couple of years ago or more, I did a test of using untinted base (oil based) and it failed. It was 3 coats of SW All Surface deep base. I placed the sample board out in the full sun and weather and after a few months the finish had split and cracked and started to flake off. I think I posted a report on it here. I have not tried the same test with water based products.

The automotive clear coat I'm talking about is a 2K poly.  That's a two-component catalyzed product.  There used to me a guy on SMC who used it for exterior wooden doors and claimed it was the only clearcoat that would stand up well over time.  I don't doubt him.  The question about whether it would work on wood, since it was designed for metal, was addressed, too.  Metal has a lot more expansion and contraction than wood, so putting it on wood is not a problem in that regard.  The problem I see with 2K poly is the price and the need to be fully suited up since most catalysts are toxic.  Despite that, I would use it on a project where only the best would be good enough, like maybe a $5K house door.

The advantage of the A-100 over an oil-based product is it's acrylic, so the sun won't yellow it, and it has UV additives in it to protect it from damage.  The OB product does not.   

John

[tomsteve]

The automotive clear coat I'm talking about is a 2K poly.  That's a two-component catalyzed product.  There used to me a guy on SMC who used it for exterior wooden doors and claimed it was the only clearcoat that would stand up well over time.  I don't doubt him.  The question about whether it would work on wood, since it was designed for metal, was addressed, too.  Metal has a lot more expansion and contraction than wood, so putting it on wood is not a problem in that regard.  The problem I see with 2K poly is the price and the need to be fully suited up since most catalysts are toxic.  Despite that, I would use it on a project where only the best would be good enough, like maybe a $5K house door.

The advantage of the A-100 over an oil-based product is it's acrylic, so the sun won't yellow it, and it has UV additives in it to protect it from damage.  The OB product does not.   

John

theres a man on the southern polyurethanes forum( SPI makes some great clearcoat amongst other products) that does furniture refinishing. he uses it often and SPI sells to a few different high end  furniture manufacturers and a couple of high end Chris craft restorers.

[fredhargis]

No, Fred, it's the waterbased one.  Someone here several years ago used it on a large cross and the durability was very good; something like 2+ years w/o the need for maintenance.  That's longer than any exterior clearcoat I've used, though I suspect automotive clearcoat would last longer.  

Now that you mention it I remember that cross. It did hold up well as I recall.

[MstrCarpenter]

2K clear coat is available in a spray bomb.

https://www.eastwood.com/eastwood-2k-dur...oogle&wv=4

I used some on new copper (compass) directionals I fabricated for a 200 yr. old weathervane. If this is comparable to the clear coat on my GMC that started to fail at around 25 years, we're good. If it lasts more than 10, it won't be me going back up there.