# int. poly used outdoors



## accidentalpainter

I used an oil-base Minwax polyurethane called "Polyshades" meant for interiors--outside on some garage doors. Four days ago. I found out today, while looking at the label again tht, even though its an oil poly--it shouldn't be used outdoors. Its hard now. What chance do i have of avoiding a total sanding-stripping nightmare? Can I apply oil ext. poly on top or will it still fail? I couldn't find anything on this topic anywhere. Thank you for any wisdom/personal experiences in this regard.


----------



## daArch

polyshades ain't even good for interior

remember, a chain is only as strong as its weakest link.


----------



## accidentalpainter

I have applied it evenly enough by use of speed and a thin pad. But my question is about seling it under clear ext. poly. You think it can't hold up?


----------



## Brian C

You could go over it with a exterior clear finish and hope it will last the distance.


----------



## Jmayspaint

Your screwed would be my guess. I've never actually seen it done with potty shades but I have seen regular Minwax stain and varnish used outside. Even top coated with spar it doesn't stand a chance. Problem is no (little anyway) UV or mildew resistance. 

Had a lady insist we stain her garage door with Minwax so it would match the interior trim. Even with two coats of spar the color baked out of it in less than a year. 

If the door gets plenty of sun I might not strip it now. Wait a few months till its destroyed by UV's and it will come off easier. If its in the shade a lot I might go ahead and strip it. If it gets impregnated with mildew it will be a real mess. 

*assuming this is a DIY case.


----------



## Ric

Hey A-P,

To begin, Minwax Polyshades are not horrible products...matter-o-fact, they are a decent grade of reasonably high solids poly. In terms of interior versus exterior, the interior product has no UV inhibitors, as JMays mentioned. Therefore, the first thing you'll notice is the color fading pretty quickly in an exterior exposure (that'd also happen when used indoor near a window)...The second thing you'll most likely experience is white specks developing beneath the poly film. These "specks" are actually water, that has been drawn to the surface by the sun's rays (in the form of a gas), then condenses in the evening when temps cool and the sun no longer is beating down on the surface. Since the moisture has condensed into water, and the board is sealed by the poly, these water droplets can no longer "soak" back into the wood. They will return to gas by day and condense back into water by night - constantly expanding (microscopically) and contracting (microscopically). Ultimately the expansion and contraction will render the poly finish weak (similar to metal fatigue) and will crack, then flake in thin slivers.

So, by now the color has faded in the poly - and the moisture & sun has weakened the film to the point of cracking. Now comes more moisture intrusion, and the wood beneath the film begins to weather "gray". You'll notice the top panel of the garage door won't be as affected as the lower parts of the door, as the top panels are more protected (shaded) from the direct rays of the sun - because of that, your top panels will remain more color-fast and maintain the original gloss far longer than the lower panels (that are now fading, and turning dull, and signs of weathering happening beneath what's left of the poly).

Sound grim? ...and think it's because you used an interior product outside? Well, yes to the grim part...but not necessarily to the interior part. The same dynamic will occur if using an exterior clear poly, even if it's laden with expensive UV inhibitors. The truth is, Clear finishes (even with UV inhibitors) cannot protect a surface from the most damaging of all elements, UV Light. UV inhibitors will protect for a while (industry estimates UV blockers will extend the viable lifespan of a clear coating by about 10%)...(if a clear coating w/o UV inh. lasts about 2 years, then w/UV inh. lasts about 26 months...or so). There's an old adage I just made up that goes - "Nothing looks richer or more elegant, than a newly varnished garage door - Until 6 months later - when nothing looks worse than a varnished garage door".

By now I'm sure I've bored you to tears and you probably forgot what the original question or topic was...But, and I expect not everyone is gonna agree with me here, clear finishes cannot provide the type of protection, nor aesthetics, as a pigmented finish (paint) is able. Pigment is the ultimate UV Blocker and deflects, or absorbs, the harmful effects of the sun's rays (think Sunscreen protection - the higher the SPF protection level, the more opaque the sunscreen is - and the very elements used to block the sun's rays, are the very pigments used in high quality exterior house paints - Titanium & Zinc Oxides).

Personally, and finally, I'd let the Polyshades run their course - then next year sand smooth, prime, then finish with a high quality EXTERIOR acrylic house paint. Good luck.


----------



## eews

Ric- 
I agree with you that pigmented finishes will be longer lasting than clear finishes in exterior applications, but do you advocate painting all exterior woodwork? on boats, front doors?

It sounds like it.

What if there is a desire to have the wood seen as wood, esp if it is fine hardwood?

There are clears formulated for exterior use, and there are ways to help insure longevity.
For example, start with something like Smiths CPES; then use pigmented stains ( dyes stains fade more quickly ) top it with multiple coats of a good marine varnish like Epifanes, or Bristol ( get the ones that cost over $100 a gal) Stay away from minwax brand if you seek better results.
Marine varnish will flex and give with the expansion and contraction of the wood- unlike poly which is too brittle. And marine finishes with UV can be recoated to replenish the UV protection.
We've done plenty of front doors that have held up quite well. It also does depend on what kind of climate you're in. Finishes last a lot longer in the Northeast than they would in Florida.


----------



## Gough

Our go-to finish for these situations in Sikkens Door and Window. It does have to be maintained, but maintenance is simple. Wash down, let dry, recoat.


----------



## Bender

accidentalpainter said:


> I couldn't find anything on this topic anywhere.


No kiddin' huh?
On a professional painter site no less:whistling2:


----------



## CApainter

Wow! Ric knows a lot about clear finishes. Before I read his post, I was going to say something similar in terms of letting the current poly run it's course with a maintenance coat as needed. Or, maybe apply one of those waterborne clears I've used in the past over what's there now. Namely, Diamond Exterior Varathane, or something like that.


----------



## Ric

eews said:


> Ric-
> I agree with you that pigmented finishes will be longer lasting than clear finishes in exterior applications, but do you advocate painting all exterior woodwork? on boats, front doors?
> 
> It sounds like it.
> 
> What if there is a desire to have the wood seen as wood, esp if it is fine hardwood?
> 
> There are clears formulated for exterior use, and there are ways to help insure longevity.
> For example, start with something like Smiths CPES; then use pigmented stains ( dyes stains fade more quickly ) top it with multiple coats of a good marine varnish like Epifanes, or Bristol ( get the ones that cost over $100 a gal) Stay away from minwax brand if you seek better results.
> Marine varnish will flex and give with the expansion and contraction of the wood- unlike poly which is too brittle. And marine finishes with UV can be recoated to replenish the UV protection.
> We've done plenty of front doors that have held up quite well. It also does depend on what kind of climate you're in. Finishes last a lot longer in the Northeast than they would in Florida.


Hi eews,

I'm not saying that at all - there are clear marine coatings that have much better success at blocking UV Rays than any architectural clear product are capable of...and many you can find at even higher prices than $100 per gallon. My point to Accidental Painters is that, while he used a product specifically designed for interior, using an exterior _architectural_ clear, is pretty much going to perform in the same way as will the interior version. 

I think we both agree that a pigmented (opaque) coating will outlast a clear finish (if all we're measuring is the amount of damage to a surface by UV light)...but, depending on exposure - as you mentioned, basic maintenance (a re-application of add'l coats of marine varnish) will be required to maintain a necessary level of UV resistance (in other words, re-varnishing more frequently than re-painting will most likely be necessary to maintain a similar newly applied appearance). 

A couple other issues to consider in the marine vs architectural finishes is (1) obviously, price...(2) clarity - or color. In Accidental Painters case, the color most likely isn't an issue since he chose a PolyShade color anyway - but for anyone wanting a "water-white" finish, he/she has few options other than an architectural clear. (Now I'm gonna show my ignorance here as I haven't really kept up with all UV inhibitors on the market) Marine varnishes generally are either of significantly greater color due to the dyes/pigments used to create maximum UV resistance, or they are generally kinda hazy in appearance as the clear pigments or fibers used to deflect the suns rays, aren't completely clear, or invisible, in a "water-white" film...and (3) the types of wood commonly used in marine environments. You mentioned the appearance of fine hardwoods, and as I said in my first post, "nothing looks richer, or more elegant, than varnished wood", but that's not to say all woods are going to "weather" as well as others. Woods commonly used in marine environments (teak, mohagany - real mohagany, etc.) are usually much more naturally resistant to weathering than are those wood commonly used in the home-building trade. So in the marine realm, protection from constant moisture exposure, salt air, etc. are of equal importance as the UV protection. 

I absolutely agree that some woods, especially the "fine hardwoods" you mentioned, need to be finished clear as opposed to being painted. And, in my opinion, the appearance of _some_ varnished woods, even in an exterior exposure, is worth the occasional, but necessary, maintenance application to preseve that appearance.


----------



## Wolfgang

Ric said:


> Hey A-P,
> 
> To begin, Minwax Polyshades are not horrible products...matter-o-fact, they are a decent grade of reasonably high solids poly. In terms of interior versus exterior, the interior product has no UV inhibitors, as JMays mentioned. Therefore, the first thing you'll notice is the color fading pretty quickly in an exterior exposure (that'd also happen when used indoor near a window)...The second thing you'll most likely experience is white specks developing beneath the poly film. These "specks" are actually water, that has been drawn to the surface by the sun's rays (in the form of a gas), then condenses in the evening when temps cool and the sun no longer is beating down on the surface. Since the moisture has condensed into water, and the board is sealed by the poly, these water droplets can no longer "soak" back into the wood. They will return to gas by day and condense back into water by night - constantly expanding (microscopically) and contracting (microscopically). Ultimately the expansion and contraction will render the poly finish weak (similar to metal fatigue) and will crack, then flake in thin slivers.
> 
> So, by now the color has faded in the poly - and the moisture & sun has weakened the film to the point of cracking. Now comes more moisture intrusion, and the wood beneath the film begins to weather "gray". You'll notice the top panel of the garage door won't be as affected as the lower parts of the door, as the top panels are more protected (shaded) from the direct rays of the sun - because of that, your top panels will remain more color-fast and maintain the original gloss far longer than the lower panels (that are now fading, and turning dull, and signs of weathering happening beneath what's left of the poly).
> 
> Sound grim? ...and think it's because you used an interior product outside? Well, yes to the grim part...but not necessarily to the interior part. The same dynamic will occur if using an exterior clear poly, even if it's laden with expensive UV inhibitors. The truth is, Clear finishes (even with UV inhibitors) cannot protect a surface from the most damaging of all elements, UV Light. UV inhibitors will protect for a while (industry estimates UV blockers will extend the viable lifespan of a clear coating by about 10%)...(if a clear coating w/o UV inh. lasts about 2 years, then w/UV inh. lasts about 26 months...or so). There's an old adage I just made up that goes - "Nothing looks richer or more elegant, than a newly varnished garage door - Until 6 months later - when nothing looks worse than a varnished garage door".
> 
> By now I'm sure I've bored you to tears and you probably forgot what the original question or topic was...But, and I expect not everyone is gonna agree with me here, clear finishes cannot provide the type of protection, nor aesthetics, as a pigmented finish (paint) is able. Pigment is the ultimate UV Blocker and deflects, or absorbs, the harmful effects of the sun's rays (think Sunscreen protection - the higher the SPF protection level, the more opaque the sunscreen is - and the very elements used to block the sun's rays, are the very pigments used in high quality exterior house paints - Titanium & Zinc Oxides).
> 
> Personally, and finally, I'd let the Polyshades run their course - then next year sand smooth, prime, then finish with a high quality EXTERIOR acrylic house paint. Good luck.


 Damn it's good to read a detailed answer. Great job!


----------

