Hello All,
I am repainting some bedrooms in my grandparents home that have not been painted for 20 or more years. It looks like someone painted over 90 year old (oil based)paint with latex and didn’t scuff sand it or prime it prior to painting it.
The latex paint will scrape off relatively easy but it would still be a big job to scrape the entire bedroom. There are 10 or so spots where the paint has started to lift off from stuff bumping into it. As we scrape the loose paint off it is hard to decide where to stop.
So my question is, is there a test for adequate paint adhesion prior to recoating with new paint?
Also would a good primer coat help in this situation?
Thanks,
Karl
Replies
Stick a piece of duct tape to it, then pull it off. If the paint comes off with it, well...
I've run into this in many apartments I've painted. You're right, you could make a career of scraping it. What I do is scrape what's loose, scuff sand the newly exposed old paint, then prime with bin. The primer helps keep the exposed edges from further peeling.
You could get plenty of tape and "Test" everything, thus removing 90% of the loose paint. It's better than scraping, but you'll still have to scrape the remaining 10% - usually inside corners and such. Optionally, you could just accept the fact that it's going to peel in some areas, and fix it every few years.
~ Ted W ~
Cheap Tools! - MyToolbox.net
See my work - TedsCarpentry.com
I wrote this:
Primer will not help the old paint to adhere to the underlying surface
You wrote this:
The primer helps keep the exposed edges from further peeling
Just to clarify, I agree with you... especially with the emphasis on HELPS
Yup, it's not an easy one to remedy.
One house where I was doing other work (tiling a bathroom floor), the painters were going over all the trim with scrapers and removing as much latex as they could. Same situation. They had 4 guys working in the living room when I got there and they did only 2 rooms before I was done. Only other option was to break out the paint remover, but that wasn't an option with the carpet and people living there and all. ~ Ted W ~
Cheap Tools! - MyToolbox.netSee my work - TedsCarpentry.com
As we scrape the loose paint off it is hard to decide where to stop.
This sentence alone bears testimony to disaster. If it isn't easy to decide when to stop scraping because further attempts yield no results, then you've got to keep going. Otherwise, as soon as you put another layer of paint on those walls, any paint that was only marginally adhered will let loose due to the water in the paint. Then the disaster grows. It's possible to use an oil-based paint to reduce the chance of this happening, but I wouldn't risk it.
Sorry, but that's how I see it. I hate it when walls are ruined by a bad paint job, especially when it would have been so easy to do it right.
Primer will not help the old paint to adhere to the underlying surface, but once you remove the non-adhered paint, an oil-based primer is a really good idea before painting again.
Google "scotch tape paint adhesion test" for a description of how to test for adhesion. I would be surprised if the paint job you describe can pass this test.
I tried googling "scotch tape paint adhesion test" and the most relevant hit on the first two pages was one for repainting auto upholstery.Even though I couldn't find a good test I get the idea of what you are describing.I suppose one question I should ask is if it will be much more difficult to do a thorough scraping in the future if I go ahead and repaint without doing extensive scraping.The only place where paint was lifting off was where door casing or chair rail had experienced some movement and the latex film had more resistance to tearing than the underlying paint had resistance to peeling/seperating.The room in question is relatively small and would probably cost me about 200 dollars in labor to scrape. The biggest "cost" in doing the scraping is in testing a great helper/laborers committment to his project by giving him such a ungratifying job. He is a good sport and will do it if it seems like the proper course of action.Thanks for the input.
I am going to run over tonite an put some duct tape on the wall and peel it off.Karl
I suppose one question I should ask is if it will be much more difficult to do a thorough scraping in the future if I go ahead and repaint without doing extensive scraping.
Yes, it will be more difficult later.
Here's a link to the adhesion test:
http://www.zinsser.com/faq_details.asp?FAQID=57
Thanks Don,
That link is exactly what I needed.
Karl
I did the tape test after crosshatching the paint and it varied from wall to wall. The worst area the entire area covered by the tape pulled up with it. In the best area only a few tiny chips broken loose by my knife in the crosshatching pulled up.I called a painter I know and he suggests scraping any loose areas, hand sand the area with 60 grit and use sherwin williams acrylic bonding primer.
It will probably set things back one day of labor but be well worth it.Thanks to all for the input.Karl
Just from my recent experience, you might want to find out if your paint pulls up with regular painters tape.
Hate to have a nasty surprise while you are cleaning up!
Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
I used 2" clear packing tape so I am guessing it is about as sticky as any painters tape will be. I am resigned to having to scrape the bulk of the poorly bonded tape off.Karl
Actually, that is MUCH MUCH stickier than painters tape. That tape is ment to be permanent, while painters tape is ment to come off without taking up paint.
Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
At this point most of top layers have been scraped off and it is waiting to be scuffed up with 60 grit. I bought some Sherwin Williams prep rite acrylic bonding primer to cover it all with and then will top coat with sherwin williams Pro Classic enamel.Karl
http://www.plasterlord.com/notebook/fcalcimine.htm
You might want to read that about calcimine paint, which your house is the right age to have. I decided re-sheetrocking a bedroom was easier than dealing with it. The previous owners had tried to stick layers of latex paint to it, which kept peeling.
You can't wallpaper over it either.
Splinter, Your experience is scaring me a little bit but I think I have a more conventional paint.Thanks for the linkKarl
I did a remodel some years back, the house had been converted from a barn in the early 1900s. Didn't know about the paint, and as a good gesture put the owner in direct contact with my painter, tried to save them some money.
I'm glad I wasn't involved in the wall finishing, there were serious bonding problems, and it got ugly.
I was lucky not to have to learn the calcimine lesson on my own. Friends of mine with a lovely old three-storey wanted their second floor wall-papered and hired a contractor through the wallpaper store. The paper bubbled like mad, the problem was determined, but the paper-hanger said he couldn't have known, the store said it was the contractor's fault, and my friends just got stuck with an amazingly bad job. Tearing it off was even a worser nightmare. You'd think it would pull easily, but nooooo. I determined mine was calcimine paint and just sheeted over it, since i was changing out the doors and windows anyway. If it had been drywall underneath, i'd have removed it, but it's plaster...no fun carting that stuff out.I hope karl reports a successful job. Shouldn't take long to find out. <G>