My house was built in 1971. After removing a think layer of popcorn, I found cardboard behind it. Does anyone know what that is? Is it safe to just paint over it?
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Edit:
Technically, JACK has the correct answer.
Realistically, here's the issue. The reason why all these holes appeared is that I didn't spray enough water at a high pressure onto the ceiling in one go. The bond between the popcorn and the ceiling was too strong for me to use a knife to separate them. To make it worse, I subsequently sprayed more water with low pressure (little by little) and try to scratch. So you see some of the ceiling is totally wet and some lost the drywall paper.
What I should've done is to use a 1 gal. pump sprayer (cost $10 in HD/L) to spray pressured water onto the ceiling and then scratch.
After learning my mistake, the rest of the ceiling got scraped off very smoothly.
Best Answer
What you have is a drywall ceiling that has had popcorn sprayed over it. You can paint over it but you'll have to repair any gouges made from scraping off the popcorn and then prime it. To remove the popcorn, spray water on it, let it soak in for a few minutes and then scrape it off with a mud knife. The larger the mud knife, the less you'll damage the drywall ceiling. It's really a messy job so cover the floor up real good.