Why do painted surfaces stick together?

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I recently painted a couple of casement windows by removing them and working on them indoors. They were correctly primed and painted according to instructions, except that due to time constraints, drying time was AT LEAST 5-6 times longer (after each coat) than recommended. In other words, just right.
I did the same with the frames into which the windows were installed. Weather was in the 70s and dry for 10 days straight, so there was plenty of curing time between coats. All parts were dry when the windows were reinstalled.
Even so, the first time I opened two of the windows after they'd been installed & closed for a couple of days, the mating surfaces stuck badly, damaging the paint in one small spot. Both primer & paint were top of the line Sherwin-Williams stuff. Finish coat was a satin finish exterior latex.
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On Fri, 22 Oct 2010 11:46:04 -0400, "JoeSpareBedroom"

The paint was not completely cured.
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You should be asking Sherwin-Williams.
nb
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On Fri, 22 Oct 2010 11:46:04 -0400, "JoeSpareBedroom"

"One small spot" pretty much tells what happened. That's where you said the damage was, so all the rest of the paint dried fine. You missed a bubble or run, and popped it when you put the windows back in. Then it glued window to frame. Only had to be on one surface. Try to be more careful. Attention to detail I think they call it. Holidays are the other side of that.
--Vic
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JoeSpareBedroom wrote:

Your last word is the magic word. Admittedly, satin isn't/shouldn't be all that bad; however, never use glossy if it is going to touch anything else.
--

dadiOH
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wrote:

Paint can take 30+ days to cure completely down to the base. The pressure of the windows pushed the uncured paint to the surface. Instant stiction.
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wrote:

I have had the same problem with windows. It's been a while since I did one, but I vowed next time I'd use alkyd (oil-base for us old- timers) which I think dries much harder. --H
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wrote:

Was it humid inside where you painted. It took maybe 6 months for gloss latex to cure and not be sticky in my basement. Things dry much faster outside , moving air makes a big difference.
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On 10/22/2010 7:30 PM, ransley wrote:

Back in stone age, we didn't paint the mating surfaces on casement windows- just applied clear sealer. The only areas where paint could fuse were where the inside face of the frame met the stop, but that is only a thin strip, so was seldom a problem. In general for applications like windows and trim, I prefer clear finishes. They seem to hold up a lot better. I know you pretty much have to paint the outside if it isn't clad, but it is easier to avoid paint facing paint there.
--
aem sends...


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responding to http://www.homeownershub.com/maintenance/Why-do-painted-surfaces-stick-together-593845-.htm Nestor Kelebay wrote: JoeSpareBedroom:
Everything you say makes sense if you know a little bit about paint, except where you come to the part where you say the paint was a top-of-the-line Sherwin Williams product.
You see, here in North America, over 90 percent of the latex paint that's made is made from either one of two different kinds of plastic; polyvinyl acetate (or PVA for short) or polymethyl methacrylate (PMMA for short).
You probably know polyvinyl acetate better as white wood glue. Primers and paints that use resins made from this plastic for the binder are called "vinyl acrylic" paints or "PVA" primers. Polyvinyl acetate is most commonly used to make drywall primers and "budget" priced interior latex paints.
You probably know polymethyl methacrylate better by the term "Plexiglas". In the paint industry, paints that use this plastic for the binder resin are called "100% Acrylic" paints. So, if you've ever seen that wording on a can of paint, it simply means that the plastic film the paint forms is the same kind of plastic that Plexiglas is made of.
Now, to answer your question:
The problem is that you did NOT use a top-of-the-line Sherwin Williams paint. If you had, you wouldn't have had the problem with "blocking" that you did. The term "blocking" as it applies to paint is the tendency for some paints to remain slightly tacky even when completely dry.
You see, adhesion is simply a hard thing to engineer out of the polyvinyl acetate molecule. So, when you use polyvinyl acetate as the binder in a latex paint, you can expect that even when the paint is fully dry, it's still going to remain slightly sticky to the touch. The ability of a paint to resist remaining sticky even when dry is referred to as it's "blocking resistance". PVA paints tend to have poor blocking resistance, whereas PMMA paints have excellent blocking resistance. Generally, top quality paints will always be made of PMMA plastic, and a PMMA plastic that crosslinks for higher film strength and harness. So, when you say you used a top of the line Sherwin Williams paint, that's the only thing that's not consistant with the rest of the details you provided.
Probably the best source of reliable information about latex paints on the internet is the Paint Quality Institute at: http://www.paintquality.com
On that site: 1. Click on the "Media Center" link at the top of the page 2. Click on the "Publications" link on the left side of the page 3. Now click on the "Continuing Education Supplements" link, 4. Download the 6 page brochure entitled "The Ingredients of Paint and Their Impact on Paint Properties", and 5. Read on Page 4 of that brochure where it says:
"For interior applications, (100%)acrylic binders afford benefits in terms of: a) adhesion under wet conditions b) resistance to waterborne stains (food stains like coffee, juice, wine, etc.) c) resistance to blocking (sticking), and d) resistance to alkaline cleaners,
but the differences are not nearly as pronounced as with exterior applications.
The Paint Quality Institute was established and is funded by the Rohm & Haas Company, who were the first to cast polymethyl methacrylate in sheets and marketed that product under the trade name "Plexiglas". Rohm and Haas were the largest manufacturer of polymethyl methacrylate plastic in North America until they were purchased by Dow Chemical in 2009. Rohm & Haas is now a wholly owned subsidiary of Dow Chemical.
------------------------------------- ..in solidarity with the movement for change in Iran.
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The Homeowners Hub site is not a help forum. It's an *advertising* forum that invades real forums (like "alt.home.repair", part of "usenet") parasitically in order to generate free advertising for itself, which continually advances its search engine placement, thereby increasing its own revenue through its click- through advertising commissions.
So the first thing you should do is write them an email and tell them to quit spamming.
Then try to find your way here through proper channels. Please do a google search on "Usenet" and post the regular way.
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On Oct 23, 1:35am, nkelebay_at_ilos_dot snipped-for-privacy@foo.com (Nestor Kelebay) wrote:

Bzzzt. You haven't accounted for Van der Waals force or the fact that you're making a lot of ass-umptions.

Excellent. Now would you please post the complete history of Dow Chemical? Oh, and water...we definitely need the history of water to understand a sticking window. Sheesh.
Instead of going on your spiel why not, gasp!, ask Joe a question, like exactly what paint did he use? If he says top of the line, and he got it from Sherwin Williams, I'm tending to doubt he bought crap paint ill-suited for the purpose...unlike your post.
Joe, what paint did you get?
R
PS Your posts are so mind-numbing that I'm reconsidering my stance on the movement for change in Iran. :)~
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(Nestor Kelebay) wrote:

Bzzzt. You haven't accounted for Van der Waals force or the fact that you're making a lot of ass-umptions.

Excellent. Now would you please post the complete history of Dow Chemical? Oh, and water...we definitely need the history of water to understand a sticking window. Sheesh.
Instead of going on your spiel why not, gasp!, ask Joe a question, like exactly what paint did he use? If he says top of the line, and he got it from Sherwin Williams, I'm tending to doubt he bought crap paint ill-suited for the purpose...unlike your post.
Joe, what paint did you get?
===================== I used this primer: http://www.sherwin-williams.com/do_it_yourself/products/multipurpose_latex_primer/?referringCategory=exterior_paint_coatings/primers /
I used this paint: http://www.sherwin-williams.com/do_it_yourself/products/resilience_exterior_acrylic_latex/?referringCategory=exterior_paint_coatings/paint /
I asked about this paint, but both of the store guys were sort of "old school" and said "Self-priming...not with old windows where there's some old paint and some bare wood. Do it the regular way."
As mentioned earlier, the windows were removed and painted indoors. I wore grey t-shirts and white sneakers while working. I used Purdy brushes. Windows were laid flat on a work surface. When they were flipped over to paint the other side, blocks were placed under the glass so the windows wouldn't be resting on the surface painted the day before. Curing time was well in excess of what was stated on the paint cans.
The frames were not laid flat during painting because my son had borrowed my floor jack, so I had no way of tipping the house on its side. And last time I did that, all the dishes fell out of the kitchen cabinets. What a mess.
I used a green ladder.
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wrote:

The ladder was definitely the problem. Please visit www.ladderqualityinstitue.org and click on the "Why ladders affect paint adhesion" link. ;)
The SW data sheet says to use an oil primer on wood under the Resilience top coats. I know you were repainting, but were there any bare wood spots? I'm expecting a "No" answer.
I'm in the habit of lightly sanding glossy surfaces prior to painting (old habits...), but the primer you used specifically says, "Adheres tightly to most surfaces, including glossy paint and paneling", so that shouldn't have been an issue.
There are a couple or three things that could have happened. There's a time limit for topcoating over the primer, both minimum and maximum. How long was it before you topcoated the sash in question? The other possiblity, the one I'm guessing happened, is that a couple or three coats on each mating surface created too much buildup and the failed area was pressed tightly together. The paint may have been "fully dry" for painting purposes, but not 100% dry on a molecular basis, so the two surfaces pressed together was enough to cause bonding on a molecular level. I was only half-kidding about the Van der Waal forces in my earlier post.
I don't know how old your windows are, or how many previous coats of paint they had on, but at some point the window has to be planed/ sanded down to allow for the new paint buildup. Most times the only way you can tell when this needs to be done is to have an adhesion failure such as yours.
Check out the pulled paint on both surfaces and see if you can tell which coating failed. Maybe it was the primer to old surface bond, or the topcoat to primer. This should help guide you in future repainting.
R
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wrote in message

The ladder was definitely the problem. Please visit www.ladderqualityinstitue.org and click on the "Why ladders affect paint adhesion" link. ;)
The SW data sheet says to use an oil primer on wood under the Resilience top coats. I know you were repainting, but were there any bare wood spots? I'm expecting a "No" answer.
I'm in the habit of lightly sanding glossy surfaces prior to painting (old habits...), but the primer you used specifically says, "Adheres tightly to most surfaces, including glossy paint and paneling", so that shouldn't have been an issue.
There are a couple or three things that could have happened. There's a time limit for topcoating over the primer, both minimum and maximum. How long was it before you topcoated the sash in question? The other possiblity, the one I'm guessing happened, is that a couple or three coats on each mating surface created too much buildup and the failed area was pressed tightly together. The paint may have been "fully dry" for painting purposes, but not 100% dry on a molecular basis, so the two surfaces pressed together was enough to cause bonding on a molecular level. I was only half-kidding about the Van der Waal forces in my earlier post.
I don't know how old your windows are, or how many previous coats of paint they had on, but at some point the window has to be planed/ sanded down to allow for the new paint buildup. Most times the only way you can tell when this needs to be done is to have an adhesion failure such as yours.
Check out the pulled paint on both surfaces and see if you can tell which coating failed. Maybe it was the primer to old surface bond, or the topcoat to primer. This should help guide you in future repainting.
R ===================
The windows are the originals from 1956, when the house was built. The next coating they'll get will consist of dead presidents. New windows, in other words. The current ones look great when they're painted, but this is Western NY. It gets cold here, and I'm tired of doing the clear plastic dance every October.
The first window I painted was a non-movable one on the garage. I started with oil primer, but the temp was so high (even with the window in shade) that the primer began to gum up as I was applying it. So, I switched to latex for the rest of the windows. Maybe that was the problem. In any case, the windows are in much better shape than they were before.
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On Sat, 23 Oct 2010 11:14:41 -0400, "JoeSpareBedroom"

I painted more double-hung windows then I want to think about. A 1/8" crack in the glazing was all I needed to redo a window. A broken sash cord meant new chains and a complete window refurb. Back then Ben Moore primer and gloss was the ticket. All oil. I'd cut out soft spots and fit with new wood. I'd replenish dried up wood with boiled linseed oil rubs. Ah, the smell of boiled linseed oil! The effortless sliding of a well-balanced and fitted window! Those were the days!
Then in '97 I bought my current and probably last house. Built in '59. The windows were already needing some work. Two years later they were looking worse. I resolved to tackle them next year. The next year they were even worse, but I managed to put my past behind me, and ignore them. It hurt a little. As the years went by I tuckpointed, put on a new roof, electrical service and central air. I did put on 2 triple-track storms where I pulled the 2 big window A/C units. Screwed one in so it was binding from the get-go too. Didn't even paint and reglaze the windows first. Didn't refit the binding triple-track either. Felt pretty bad about all that.
As the years went by my wife's garden flourished, the town put new sidewalks in, redid the street and put in all new curbs. My house looked real nice - except for the windows. Every year the windows looked worse, just terrible. I felt bad when I looked at them. But not real, real bad. Pretty easy to think about something else. The triple-tracks storms were in bad shape too. Latches broken off, binding, sweating and icing in the winter.
My wife never complained about me not doing the windows, because she wanted swing out casement windows. She hated the double-hung windows. I swore by double-hung. All I ever knew. No way I would pay for new windows when I already had windows. That's just silly. Every year I told her she'd like them when I fixed everything up. She just smiled or frowned, depending. And I felt guilty every fall past painting season because I hadn't done a thing with the windows. Wasn't too hard to put the guilt aside pretty quick, but it would pick up again in the spring.
Then I heard from family about a guy who worked in a factory that made vinyl-clad thermopane windows, and had a side business installing them. Cheap. Compared to the big outfits, real cheap. Had him over, had the wife select what windows she wanted, and all my window problems were gone in a couple days. 26 windows - every one, including the basements. All window maintenance gone. Frames flashed with white aluminum. Cost 4500 President Washingtons, and worth every one. Been about 5 years and all the windows look good, work fine, there's no drafts and my heating bill isn't worth talking about. I sleep well once again.
It's real nice not having those old windows nagging me. But the best part was how proud I feel when I think about how lazy I was never painting those old windows. Didn't expect that bonus. First time being lazy worked out for me. Not that I recommend that, but you should give it some thought.
--Vic
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LOL!......
great story.
nb
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Oops. Forgot the link for the paint I *almost* chose: http://www.sherwin-williams.com/do_it_yourself/products/duration_exterior_acrylic_latex/?referringCategory=exterior_paint_coatings/paint /
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<stuff snipped>

Nestor, since you seem to be quite knowledgeable about adhesion technolgy, I have a question I hope you can answer. I have several large sheets of very expensive Plexiglas I bought for a project in 1984. Now that I am getting around to it (there's a l-o-n-g lead time around here!) I find that I cannot remove the protecting paper. It's immune to water, soaking, and nearly every solvent I have tried. It's stuck tight.
Do you (or does anyone else) know how to remove the brown protective paper after it's been sitting for 25 years?
-- Bobby G.
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I've removed ancient bumper stickers using vegetable oil. Might be worth a try. It needs to soak for a length of time known as X, where X equals "long enough".
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