Sometimes, it is a good idea to strip off existing paint on a wall before putting new paint on. The main reason for this is because the paint is unsound, i.e. not sticking properly. This can be the case when primer was not put on before painting.
Dad and I are redecorating the house and previously found the paint to be unsound. For the red feature wall it was easy to strip the paint because I had already painted it multiple times, as indicated in the hyperlink. This raised a disturbing question about how sound the rest of the paint in the house was.
Checking Soundness of Paint
There is a way to check the soundness of paint besides painting on it several times, fortunately. Simply cut a cross on the wall with a box cutter or pocket knife, put sticky tape on it and see if it pulls the paint off. For a more rigorous test, consider duct tape - in fact that may even pull the paint off without needing to cut a cross.
My cat loves to help, especially when I'm on the floor.
If the paint comes off, consider stripping the paint and starting from bare plaster.
Stripping the Paint
If you need to strip the paint off, you could use paint stripper but it really stinks and probably isn't very good for you. Therefore, I'm going to show you how to do it without chemicals.
First, use a box knife to cut along the top of the wall. You will need a step ladder to reach. In places where caulking filler was used (unusual but was the case here), cut deeply until you feel the roughness of the render. We want to replace caulking filler with proper wall filler where necessary.
Use the box knife to cut a bit below the top cut. You will use a flat scraping blade in the next step - go down the width of the blade.
Use a sharp scraping blade to strip the brush painted strip of paint along the top. Use a tool similar to this GLASSGUARD™ Glass Scraper Tool.
Use the box knife again to cut lower again according to the width of a wider scraper.
Use the wider scraper - consider one like a Craftright Scraper. We want a somewhat more blunt, wider, flexible scraper.
In areas where you are struggling with the more blunt scraper, use the sharper one. Also consider using a steam cleaner and waiting about 5-10 mins. Here, you want to wet the plaster underneath so the paint comes off more easily. If you try to scrape the paint off straight after steaming it, it may be too soft and sticky to come off. Too long and the wall dries out. I have also read about using a 50-50 mixture of vinegar and water but have had little luck.
The paint can cut - consider gloves, especially when using the sharp blade to scrape it off in strips. If you try and scrape large areas like below you can avoid getting cut.
This is an example of a wall where the paint comes off easily:
Here is a video of stripping using a Monster steamer (note this is an early attempt where we tried to start from the middle of a wall):
Larger pieces of paint (about 300 mm long) can go straight in the wheelie bin, smaller pieces and dust should go in a plastic bag.
Full painting instructions here.
Good luck! 🍀
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