I have recently purchased a home built in the 1950s. The kitchen, hallway and living room have 1 or 2 coats of latex paint on top of what I think is oil-based paint.
My problem is that the latex paint scrapes off easily with my fingernail. And I’d like to repaint these rooms.
1) Do I need to scrape all of the latex topcoat off, seeing as my fingernail can scrape it off easily everywhere?
2) Can I use a shellac-based sealer or similar product on top of the current peeling/scraping latex paint and then, paint over it, instead of scraping and sanding all of the existing latex paint off?
3) Should I be concerned that the oil paint underneath is toxic/lead-based?
4) If I do need to scrape all the newer latex paint off, what’s the best way to do it… with water and a scour pad or???
The loose latex needs to come off. There isn't a primer that can glue it to the underlying oil based paint. Adding another layer on top of the latex paint would simply be a thicker layer that will peel.
Removing this layer will be difficult and time consuming. Try using hot water and a scouring pad. This should work well. For loose yet stubborn spots use steel wool and water or a paint scraper.
It is possible that the underlying oil base paint has lead. This is always a possibility with a older home. Using hot water will lesson the risk. Don't worry if some latex paint won't come off. This can be primed over.
Once the loose paint is removed prime with a good oil based primer. This will seal up the old paint. Now you can paint with a good acrylic paint.