- Sand off tops of "popcorn bumps" with rotary sander or multi tool (like bosch multi-x).
- Spray with vinegar and water.
- Use elbow grease and a scraper.
If the popcorn finish is fairly even throughout, and you can afford to lose just a bit of headroom, one method is to skim over it with thin wallboard (3/8 is generally available and 1/4 can be special ordered). This is put up in sheets and screwed to the underlying structure (which needs to be located with a stud finder or the poke-with-an-awl method). Then taping, mudding (filling the joints), sanding the joints and painting. Sounds like a big job, but usually less time consuming than taking down the popcorn surface.
A friend of mine removed the popcorn from the ceilings and it was quite the project / mess.
Water if it soaks through to the drywall can damage the paper on the drywall. If that happens, you'll need to cut out the damaged paper, prime, patch with a joint compound (finish the surface) then prime and paint
I would probably just try using a putty knife or drywall knife - 6 inches maybe? And scrape it off.
If you were gonna drywall over it like bib said, remove the old drywall first. Why leave it up there? Cut the corners, pull down the drywall / screws and re-drywall properly. Cost difference between 1/2 inch drywall and 3/8 or 1/4 is negligible and in the process, may allow you to run electrical for new lighting, ceiling speakers, etc...
I agree with Mario on the hesitation to use any liquids on drywall. If you don't want to replace the drywall (which is a good suggestion), then this would be my process:
After knocking off the loose popcorn with a drywall knife, I'd make a pass or two with a screen sander on a pole, and then one final pass with a wide drywall knife to knock off any high spots. Then clean the surface of dust and apply a layer of premixed joint compound over the entire surface to cover all the blemishes. Keep the layers thin and you may consider adding a little water and dish soap to the mix to make it apply smoother (tip from Shirlock). Use a wide drywall knife and do your best to avoid any ridges. Lightly sand the result with the same screen sander on a pole, fix any small blemishes with a sponge sander, cleanup the dust, and paint.
Realize that popcorn is frequently used to hide blemishes and a poor quality drywall installation. So before applying the joint compound, I'd shine a light at a sharp angle to see your problem areas.
just NO to pretty much every answer given here. remove your popcorn in half an hour
- get enough plastic sheeting that you can tape it from the very top of your walls, drape over furniture, right across floor. Tape it all together so it is one big sheet, neatness does not count
- get a backpack water sprayer and really soak the ceiling
- soak it some more
- wait, no really, wait, if it is not well soaked through you will wreck it
- with a wide edged scraper GENTLY start pushing with the edge as close to level as you can do it. the popcorn will EASILY fall off, if it does not, you need more water and more waiting.
- it will all slide off quite easily, you may need to occasionally re-wet but really, probably not, don't rush, let it slide off
- when done, double check, make sure you didn't miss any, now peel the plastic from the wall, roll it all into the middle and throw it away.
- perfectly clean room, perfectly flat ceiling
- leave the room to ventilate, the drywall will dry, use a fan if need be
- if you have a problem with mold existing in your house, mix a ten percent solution of bleach and water and spray affected areas, thats it, cheap and easy fix. you don't have to soak it, just let the mixture seep into the paper
I am in the process of removing the popcorn from my 4th room in my 1970's house. In my opinion, the only reason I would have wet it was to cut down on the dust because more than likely it's full of asbestos so mask up. Other than that it came off quickly with no problem. You will have to re-mud the entire ceiling where all the seams and nails are and tape/mud the entire edge. Where the wall meets the ceiling can be damaged during the scraping process and eventually you will develop a crack where the paper tape was damaged so don't skimp on that or you will really regret it, trust me on this, fixing it after the fact is another bummer..... removing the popcorn and fixing the unfinished ceiling totally sucked but it looks so great!! I Kilz everything and then ceiling white the ceiling and paint the walls. Good luck and just keep thinking about how great it's going to look when you are done!!