UV protectors....

Finishes, paints and coatings

UV protectors....

Postby JaggedEdges » Tue May 03, 2016 2:26 pm

Hi Folks,

I started looking into using aircraft dope for a top finish over canvas. I somehow had the idea that it was cheap to get surplus still in this day and age. Nope. Maybe if certification expired. Nope... anyway, during that spell of digging for info, an interesting piece of info came up. In the 20's and 30's they were painting the stick and string jobbies with silver dope. Now I thought that this was an affectation, trying to make the old but still effective stick and string tech look like shiny new aluminum monocoque..... not so, they were using aluminum powder in the dope as a UV protector. I guess in the early days designs were changing so rapidly that nobody gave a thought to UV stability of everything, but as given aircraft began to be in service years, they came up with using the aluminum powder to prevent UV penetration. Often this was an underlayer, they'd shoot color on top of it, and the color might fade, but at least your wings weren't gonna fall off or the canvas part company with your wig ribs because the glue got fried.

So, what we get from that is, aluminum powder stops UV.

Also somewhat famous for the job is titanium dioxide which has been the default white pigment. However, paint manufacturers seem to be shy of telling you their white pain is already stuffed full of it maybe and will thus rpotect better... Or they have found something cheaper to use that isn't as good and only stick Titanium dioxide in the spendy exterior stuff now.

Zinc oxide is oft used in combo with that, I think it protects better from a different wavelength, not sure how good it is in paint and coatings. I tend to think of it as a bit slippy like graphite, so wonder if it makes things crumbly.

Anyway, upshot of that is, I'm wondering about cheap waterproof polyurethane, that's specified as indoor only, then getting myself some aluminum powder and mixing it in. What we should expect with that though is still some surface checking and chalking and dullness, after long exposure, but it protects "in depth" as it were.
Jack of all trades, Doctor of rocket surgery and fellow of the noble college of shadetree meddlers. "in argentum tenax vinculum speramus"
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Re: UV protectors....

Postby greygoos » Wed May 04, 2016 1:38 pm

Not sure if this will help but there is a build on here that uses off the shelf aluminum paint over canvas. It is in the foamies section
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Re: UV protectors....

Postby JaggedEdges » Wed May 04, 2016 8:28 pm

Yah that used to be a thing you could get here, a generic aluminum paint that was great for everything, they kind rolled it into the rust paint lines now. But before it was one of the cheapest commodity exterior paints. 5 years ago I tried to get some, and got the "Humor the crazy person" look from staff at all the local hardware stores.
Jack of all trades, Doctor of rocket surgery and fellow of the noble college of shadetree meddlers. "in argentum tenax vinculum speramus"
JaggedEdges
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