Q: What is the best way to paint a ceiling with “popcorn” acoustical texture that is discolored in some spots?
A: First, clean the ceiling with a brush nozzle on a vacuum cleaner hose. To conceal the discoloration, you should apply a stain-blocking interior latex primer. Use a quality synthetic roller cover with a half-inch nap. Open a couple windows while applying the primer and leave them open to help it dry. Allow the primer to dry at least overnight, then apply a wall paint with a dead flat sheen using the same size roller nap.
