While it might not be the end of the world, a crack in the ceiling paint can be a pain in the neck. It starts by marring your pristine ceiling -- the one area the kids can’t reach -- and ends by occupying your time on a weekend afternoon to restore the ceiling to its prior glory. Fortunately, with a little patience you’ll have your ceiling looking brand new again very quickly.
Move the furniture out from under the area of the ceiling with cracked paint, if possible, and cover the area with a drop cloth. If you can't move the furniture, just cover it up with another drop cloth.
Scrape off the cracked paint with a metal putty knife or a paint scraper. Scrape away any flaking paint surrounding the crack as well to create as smooth a surface as possible. Continue to scrape until the area is completely free of any loose paint. Use the medium-grit sandpaper to remove any rough spots in the area and sand the edges of the paint surrounding the crack.
Wash the area with a mixture of 3 parts water to 1 part mild dish soap, using a sponge. Allow it to dry thoroughly.
Take a very close and careful look at the ceiling where you removed the cracked paint and inspect for any crack lines in the ceiling. If there are no crack lines, the problem was a result of the paint. However, if you notice a crack in the ceiling, the underlying cause could be more extensive. In this case, have the ceiling inspected by a professional to ascertain any structural concerns. Afterward, you can fill the crack line as you repair the paint.
Press the spackling compound into the crack in the ceiling -- if you found one and it has been inspected -- with a putty knife and then spread the spackle over the entire area where the paint was removed. Allow it to dry according to the manufacturer’s instructions, and then sand the compound smooth with fine-grit sandpaper.
Feel for any ridges when you're finished sanding -- there should not be any when you run your hand across the area that was sanded to the area that was not. If you feel ridges, apply a thin layer of spackling compound with the putty knife, fanning out the edges. Allow it to dry and sand it smooth.
Apply primer to the area that has been covered with the spackling compound. Allow it to dry, and then apply a coat of the same paint you used on the rest of the ceiling. Allow it to dry, and apply one more coat.