How to Spackle a Ceiling Using Joint Compound

Start on one seam's end and run a strip of drywall tape down the seam's length. Center the tape over the seam and push it firmly onto the drywall. Flatten out any creases in the tape.

Cover the floor with a painter's cloth to protect it from any dropped joint compound.Dig some joint compound out of the bucket with a 6-inch drywall knife. Place the compound into a mudding tray.

Hold the drywall knife at a 45 degree angle to the ceiling and spread the compound down the seam. Make this first layer approximately 1/4-inch thick. Apply the compound down the entire length of the seam. Scrape more compound out of the tray as needed.

Wait for the first layer of compound to dry. Once dry, if you notice any ridges, sand them away with a sanding sponge. Apply a thinner second layer of joint compound the same way you did the first layer except use an 8-inch drywall knife. Feather the edges of the second layer so the compound is thicker in the center then gradually reduces to nothing as you get closer to the sides. Accomplish this by holding the drywall knife's blade at a slight angle as you spread the compound.

Sand any ridges off the second layer of dry joint compound. Apply the third and final coat of joint compound using a 12-inch drywall knife. Feather out the edges the same way you did for the second layer. The joint compound now extends 9 to 10 inches past the seam on either side to blend the seam into the drywall's surface.