Instructions for Knockdown Ceiling Textures

Cover the walls and floor in the room with plastic tarps, held in place with low-tack masking tape.

Connect a hopper gun to an air compressor with an air hose. These tools can be rented from most major hardware stores.

Set the air compressor to between 30 and 40 PSI. You can adjust it later if the pressure is too great or too little.

Mix a batch of all-purpose drywall compound following the instructions on the container. This is typically done in a bucket, using a drill with a paddle mixer attached. Thin it down with additional water until it has the consistency of runny pancake batter.

Fill the hopper one-third of the way full with thin drywall compound. You will have to refill it frequently, but if you add more you run the risk of it spilling out as you point the gun upward.

Set the hopper gun's nozzle to a medium setting using the rotating wheel on the front.

Spray the drywall compound from the hopper at a piece of cardboard. Adjust the air pressure until the size of the splatter is where you want it. This is a personal choice depending on how textured you want your wall, but heavier textures tend to hide more flaws.

Spray drywall compound onto the ceiling, working in smooth, overlapping strokes. Keep the gun moving at all times to prevent thick areas from building up on the ceiling. Don't try to get total coverage; there should be empty spaces between the blobs of compound.

Let the ceiling dry for 10 to 15 minutes. Rinse out the hopper gun with water during this time to prevent the drywall compound from drying in it.

Lightly wipe the ceiling with a knockdown knife, which looks like a wide scraper. The blobs of compound will flatten, becoming a knockdown texture. Work from the edges of the ceiling in toward the center. If there are lines of compound forming at the side edges of the knife, it is not dry enough yet. Wait five minutes and try again.

Wipe off the knife with a rag regularly while you knock down the texture on the entire ceiling, working in the same basic pattern that you applied the drywall compound.

Let the ceiling dry overnight, then prime and paint it as desired.