An acoustic "popcorn" ceiling, also known as a “cottage cheese” ceiling, is a spongy material applied to finished drywall by a compressed-air sprayer. Like acoustical tile, popcorn ceilings were installed to form an attractive textured surface, dampen sound and reduce or eliminate echoes.

 

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Grease, tobacco smoke, and dust and dirt in general, accumulate on and readily discolor this kind of ceiling. But before you touch it or start cleaning it, have it tested for asbestos content. If asbestos is present, you'll want to leave it alone and let the professionals handle it. Asbestos materials are considered to be safe, so long as they remain intact and in good enough condition that no fibers are wearing off creating dust that can be breathed.

Assuming asbestos is not present, vacuuming does not work well, other than for removing some attached cobwebs. Acoustic popcorn adheres to the underlayment very loosely, so it's easy to suck or knock off the surface. Stains can often be removed by spraying a bleach-based chemical onto the ceiling; the chlorine bleach strips colors out of the materials.
Contractors are available to do this work.

Popcorn ceilings can also be painted, but may need to be cleaned first. Bear in mind that painting may reduce or destroy the effectiveness of the acoustical material.

 

 

Reference:

Don Aslett in The Cleaning Encyclopedia: Your A to Z Illustrated Guide to Cleaning Like the Pros