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SGTHetland 08-14-2008 07:06 PM

Paint will not stick in Bathroom!
 
3 Attachment(s)
My parents have spent quite some time now trying to paint their walls in their bathroom. In areas above the shower and along the partition walls, the paint fails to stick and is easily peelable. Along sheetrock joints, the paint is peeling as well. Supposedly years back paint was applied over wallpaper. Primers have been used (kilz) and still nothing works. Can't seem to figure out what will prevent this or how to fix it. Any thoughts?

Nestor_Kelebay 08-15-2008 12:02 AM

SGTHetland:

If the peeling is worst directly over the tub or high up the walls near the ceiling, then the problem is most likely in the paint they're using, and has nothing to do with the primer under it. In fact, it's common to use a PVA primer in a bathroom and top coat with a bathroom paint. If you didn't understand that, read on...

In your pictures, the very first one is typical of what happens when you use a PVA paint in a wet area like a bathroom.

I think the other two pictures show a seam in wallpaper that's been painted over.

Here's the short version:

Your parents need to use a paint made for bathrooms, like Zinsser's Perma-White Bathroom Paint, or any competitor's equivalent. Such paints will be made from a plastic called "polymethyl methacrylate" or "PMMA" which you know better as "Plexiglas".

They don't have to do too much. From what I can see, the paint on their walls now is a fairly low gloss. If it's a latex paint, they can just scrape off that peeling paint, scrape away any loose plaster under it, patch with drywall joint compound, sand smooth, prime over the bare joint compound, and then repaint with a paint meant to be used in bathrooms. (Cleaning the old paint first and allowing time to dry would be a real good idea too.) The top coat of PMMA bathroom paint will keep the underlying paint dry, so it won't peel.

Here's the long version:

Most latex paints and primers made in North America are made from one of two different kinds of plastics:

1. Polyvinyl acetate or "PVA". Polyvinyl acetate is what white glue is made of. It makes a good plastic for making paint from because it sticks well, it's cheap and it's clear. PVA has a lot of problems. It's a great adhesive, but the problem is that it remains slightly sticky even when it's completely dry, and that causes problems with paints. The other thing is that PVA has LOUSY water resistance. That means that it's properties change when it's wet. It softens up. It looses it's adhesion to the substrate. And, in the case of wood glues, it even re-emulsifies. That is, it dissolves (kinda) into the water. In fact, the way furniture makers take apart furniture that's been glued together with white wood glue is by getting the joints wet so the glue falls apart.

That first pictures shows what happens when inexpensive PVA paints get wet or are even in a humid environment; they soften up and lose their adhesion to the substrate... that is, the paint film comes apart and starts to peel off the substrate. And then the plaster under the cracked and peeling paint starts to get wet too.

2. Polymethyl methacrylate, or "PMMA". Polymethyl methacrylate is what Plexiglas is made of. PMMA resins are simply better than PVA at everything when it comes to making latex paint except being inexpensive to buy. However, not all PMMA resins are equal. There are literally hundreds of different kinds of PMMA resins used to make everything from nail polish, acrylic floor finishes, grout sealers, concrete bonding agents, adhesives, additives for different kinds of cements AND latex paints and primers. Generally paint or primers made from PMMA resins are better than paints or primers made from PVA resins at:

i) sticking to damp or moist substrates
ii) not changing their film properties if they get wet
iii) standing up to highly alkaline substrates, like fresh concrete

But, normally to avoid problems with the paint remaining sticky after it's fully dried, to get better UV resistance, to get a harder and more durable film, or a film more resistant to acids, you're better off spending a bit more and getting a paint made with PMMA resins. (They can increase hardness and UV resistance in PVA paints with crosslinking resins and UV blockers, etc. but PMMA resins are inherently better than PVA in all these catagories to begin with.)

Any paint or primer that claims it's "100% Acrylic" will be made with PMMA resins. However, there are very many different kinds of PMMA resins, so the paint manufacturer has to decide on what characteristics are most important in the paint he's making.

Anyone making a paint specifically for bathrooms will not only use the MOST water resistant PMMA resins they can find, but will also add mildewcides which dissolve in the water based paint and leach out of the paint film any time it gets wet to kill any mildew spores that land on the paint before they can grow. Thus, a paint made specifically for bathrooms is the best kind of paint you can use in a bathroom. duh.

There, now you know more about the plastics that latex paints are made of than most people working in the painting industry.

I use Zinsser's PermaWhite in my 21 bathrooms, but ANY paint specifically made for bathrooms should provide much better service than the paint shown in your first picture.

Hope this helps.

chrisn 08-15-2008 04:54 AM

Above and beyond all that was said above, the best would be to remove the wallpaper and start with a fresh wall.

sirwired 08-15-2008 02:15 PM

Bathrooms are tough adhesion environments. At this point, I don't think wall-paper removal is an option... once it has been painted over, it's real tough to do.

First, ALL of the loose and failing paint needs to be aggressively scraped and sanded. If it is sticking, you can leave it there, but if it is loose, no topcoat is going to work.

Next, wash down the surfaces w/ a TSP solution; this will help to remove all the nasty residue that typically sticks to bathroom walls. Rinse.

If you have any loose wallpaper edges, glue them down.

Prime with a bonding primer... water-base should be fine, but you may want to try oil-base. I don't know much about paint chemistry, but you don't need to know anything to ask the guy behind the counter at a paint store for bonding primer. (I personally use Sherwin Williams PrepRite ProBlock Latex.) Whatever you do, do not buy your primer or paint at BigBoxCo. If you used Kilz2 as your primer, that is possibly the cause of a lot of your problems right there... it's an awful product.

Topcoat with a quality specialty bathroom paint from a paint store or Zinsser PermaWhite.

If possible, do not use the bathroom for showers or baths a week before or after the painting.

SirWired

slickshift 08-15-2008 05:34 PM

Quote:

Originally Posted by sirwired (Post 148941)
...I don't think wall-paper removal is an option... once it has been painted over, it's real tough to do.

Interestingly enough, sometimes wallpaper removal is facilitated by first painting it

Not having my hands on this particular project to test it, I can't say if it's an option in this case, but it should be attempted...at least tested
I can say that the vast majority of paint-overs are done as short-cuts rather than it was the "only alternative", and are doomed to failure
It may take time...
Like this case has shown
I can also say that in this particular case (a tough environment bathroom, unknown previous products and prep, known poor products used with unknown prep), it would be most desirable to remove the wall covering

If removal is actually not possible (not merely an inconvenient labor and expense addition), then the room must be scraped and sanded
Then cleaned thoroughly
Often the usual paint prep cleaners are no match for the horrors of the bathroom (Glade/HairSpray/Perfumes/Candles)
I'd suggest using a few different ones at safe intervals to ensure the best surface prep
A specialty primer used (depending on what's left probably Zinsser's Gardz)
Joint compound repairs made, and the repairs or the whole thing re-primed
Then a few coats of premium self-priming Kitchen & Bath or other self priming washable mold resistant paint (Ben Moore/Sherwin Williams K&B, Zinsser's Perma-White, Ben Moore's Aura)

chrisn 08-15-2008 06:34 PM

I can also say that in this particular case (a tough environment bathroom, unknown previous products and prep, known poor products used with unknown prep), it would be most desirable to remove the wall covering


Thank you,slick:thumbsup:

dll 08-16-2008 09:08 AM

Sorry to hijack this thread, but I have to thank you all so much for the information on the bathroom paint! It is just what we were looking for. Do you know how this paint holds up to cold temperatures?

We have a small bathroom with shower, sink and toilet and the washer and dryer. Also, we have a south wall that catches a lot of wind in the winter and can get very cold.

We've had trouble over the years trying to get anything to work in there. We took the wallpaper off when we moved in because it was coming off on that south wall and other places. Then we painted, but it started peeling just like that first picture. Next, we put up tile board. I don't know if it was defective or just couldn't handle our room, but it has started flaking/peeling off behind the sink, toilet, shower and near the floor where water sometimes gets.

So now we're back at square one. We thought maybe a different paint would work (possibly like what you talked about), but worry about that south wall and the coldness there. Any other suggestions that might work. (It's a very heavily used bathroom since we farm and that's where everyone washes up)

Sorry if this needs to be a separate thread. Let me know if I need to do that. I was basically wondering about this paint that you mentioned. I'm glad I discovered this site. IT looks very helpful.

Nestor_Kelebay 08-16-2008 01:16 PM

Dll:

Providing you apply a paint made for bathrooms (like Zinsser's PermaWhite) when it's not cold in the room so that it adheres properly and forms a proper film, it should stand up as well as any other paint when it is cold in the room.

dll 08-17-2008 09:56 PM

Thank you for your reply! I think this might be what we've been looking for.
Quote:

Originally Posted by Nestor_Kelebay (Post 149180)
Dll:

Providing you apply a paint made for bathrooms (like Zinsser's PermaWhite) when it's not cold in the room so that it adheres properly and forms a proper film, it should stand up as well as any other paint when it is cold in the room.


Nestor_Kelebay 08-18-2008 12:04 AM

Glad to help.

I think a big part of the problem is that most people aren't aware that latex paints are made from different kinds of plastics, and that some plastics are more suited to wet areas than others. So, you can do a really good job prepping a bathroom for painting, but still end up with paint cracking and peeling problems if you use the wrong KIND of paint.

If people aren't aware of that, then they always keep coming back to blaming the paint peeling problems on poor prep work. And, that can be perplexing to the homeowner who knows he bust his butt doing the best prep job he possibly could have.

I'm wondering if the same thing may be responsible for the concensus of opinion in this forum that the unique conditions in a bathroom make it hard to get paint to stick well.


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