Keeping Paint From Skinning Over In Can

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Old 09-05-07, 09:42 PM
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Keeping Paint From Skinning Over In Can

I have a custom door business and I use quite a bit of Spar Urethane. But there are times when I might not spray a door for several days and a good amount of urethane skins over in the can. One reason is that I use an airless sprayer and it sits in the can all the time. No real good way to seal it up. Sprayer has not been dry, out of a can of Spar Urethane in 13 months. Keeps the sprayer and hose full all the time.

But here is the question. Air (Oxygen) is what causes the Spar Urethane or even Paint to skin over. In fact a full can of Spar Urethane that has a skin over it keeps pretty well for a week or more if necessary. But with usage over several days I might get 3 or 4 skins inside the can. Then chunks break off and sometimes get hung up over the pick up tube. I have been researching heavier than air gases and have found the new type air in the can like "Dust Off" to blow off your computer and such are now using Nitrogen as the gas that blows out. If I should spray a little squirt of the Nitrogen gas into my Spar Urethane can each day it would seem like the heaver than air Nitrogen gas would replace the Air (Oxygen) in the can and therefor keep the Spar Urethane from skinning over because there would be no air.
But my real question is does anyone think that the Nitrogen might or could react with the Spar Urethane to cause any problems with it. $5.00 can of gas and $30 gallon of Spar Urethane would be a waist if it didnt work or even ruin a $2000 door, finish job.
I'm really looking for some opinions about that before I tried it
 
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Old 09-06-07, 04:08 AM
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you should have no reaction. I sell a two part urethane for exterior doors about $30-40 per quart and we use a nitrogen blanket for these items every time. Otherwise the catalyst will react with the O2 in the air and go bad. I use the bloxygen brand and have no issues with it in oils or urethanes.

Just for curiosity, have you looked at the two part urethanes for your doors? They will outperform any spar varnish on the market.
 
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Old 09-06-07, 05:03 AM
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I'll go along with B.C.

I use UTC colors in mixing my own stains for furniture work. Use Bloxygen before recapping the can to prevent skinning over. Haven't had any problem and it's sometimes months between uses for a particular UTC.
 
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Old 09-06-07, 09:15 AM
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2 Part Urethanes

In the south I need as much UV protection as possible. Wood Finishers Supply is our local supplier of catalyst urethane's and they have no UV protection. One door guy here in the area has re-done 8 or 9 doors that faded out in 9 months or less because of the Urethane he used. I am not usually in a huge rush and I don't mind the 4 hour between coats with the spar urethane from MinWax and have good success with it for years. But I do use Wood Finishers Supplies stains because they cover better and dry much quicker than the MinWax stains.
 
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Old 09-06-07, 04:28 PM
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NEVER use minwax. it is the worst stain on the market. I cannot count the number of problems I have dealt with that are directly related to those stains.

I am not a fan of any Minwax product, I have found them to be inferior to other, professional products.

from Minwax's website on the spar varnish "...contains over 100% more UV blockers to reduce the sun's graying and fading effects." 100% more then what? Remember an UV inhibitor is a self-sacrificing product. eventually the product will fade and yellow from UV exposure. I have found that in order for a UV inhibitor to work well you need about 3-4% by volume. This may not seem like much, but a gallon of said inhibitor retails for about $200 a gallon, that 3% can get quite expensive. Thus I question just how much Minwax has added to it's product.

Depending on the 2 part urethane you look, some have those UV inhibitors added and you should be able to add more if you desire. Overall a good urethane will blow a spar varnish away.
 
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