Clearcoat Test-Finish Update

Maybe a year ago, there was a discussion, here, regarding using a paint base, without the tint added, as a clearcoat finish on an exterior project. This past spring, I stripped and refinishied a swing with 3 coats of Olympic Fast Hide Ultra, Int/Ext Alkyd Gloss, Base 5 - #218156 (directions on the can- "Must be tinted").... no tint added.
I don't detect the finish, itself, failing, yet, but it sure has blackened with mold/mildew, horribly so. When new (I made the swing), I had finished it with Spar Urethane and there was no such molding/ mildewing/blackening build-up in the 5 years the Spar Urethane was on it. The swing has always been hung under the same oak tree and pretty much completely shaded, so the Spar Urethane held up well. The swing is made of ER Cedar.
I'll clean the swing and see what the finish looks like, under the black. As of now, I would not recommend using a paint base as a clearcoat finish for an exterior piece.
Sonny
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When did paint bases start being produced clear? I have never seen anything but white for the base.
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I was not very knowledgeable of this sort of clearcoat until the earlier discussion and, later, speaking with a painter friend about the discussion. There are different bases and they are numbered 1 thru 5. If I recall, the higher the number the more clear the base will be, when applied or dry. I normally use waterlox for most exterior pieces, but I was interested in testing a paint base as an option for an exterior finish.
I've applied BLO on cypress and it has developed a blacken appearance, that, from a short distance, looks like a build-up, but is not a build- up, as with this swing. It just darkens, somewhat. The build-up on the swing has to partially be dust and such, then it molds or mildews. It may also be the finish, itself, is molding and/or mildewing. I haven't started the cleaning, yet, to see what may actually be going on.
My friend did mention the VOC issue, also, and the less availablity of those types of finishes.
Sonny
The #5 base I used had a gray, opaque color in the can, but was clear on application and when dry. My painter friend said the base has no UV protection... that it is the pigments, normally added, that would protect against UV damage. Again, on the swing, I can't see, yet, if the finish, itself, has any damage. I certainly don't like the blackened build-up and I attribute that to this base's resistance to such build-up. The spar urethane didn't show any build-up, as this. I didn't expect the spar urethane to last as long as it did, but the swing was in good shaded cover.
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Thanks for that explanation!

I was not very knowledgeable of this sort of clearcoat until the earlier discussion and, later, speaking with a painter friend about the discussion. There are different bases and they are numbered 1 thru 5. If I recall, the higher the number the more clear the base will be, when applied or dry. I normally use waterlox for most exterior pieces, but I was interested in testing a paint base as an option for an exterior finish.
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When light pastels and white. When I get black they use dark but add 12 ounces of carbon black to a gallon. Then it is BLACK!
When I get White - they use a clear and add metal oxides. Just not lead. This is for metal paint. It isn't interior - but exterior metal.
Martin
Leon wrote:

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On Tue, 29 Dec 2009 20:35:14 -0600, the infamous "Martin H. Eastburn"

Dayum!
Titanium dioxide is the goto white pigment.
-- It's a shallow life that doesn't give a person a few scars. -- Garrison Keillor
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RE: Subject
There are some two part, catalyzed marine clear coat finishes available, but due to VOC content, sale to the general public is becoming a thing of the past.
Lew
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Sonny wrote:

You put on what is essentially varnish.
Paints have different bases to facilitate tinting...if you want a light color you start with a light base - one with lots of white (generally, titanium dioxide). Deeper bases have decreasing amounts of that so that they can be deeper in color. Decreasing the titanium dioxide increases transparency.
You would do better just following the manufacturer's instructions vis a vis paint selection.
--

dadiOH
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