The Sacramento Bee (California) shares with its readers a tip from Heloise on using vinegar to clean terra-cotta planters (i.e., eliminating the white film on the side of pots). Heloise notes,
To keep the white stains at bay, brush an acrylic sealant onto the pot, inside and out.The white film is actually hard-water deposits … Using some dish soap and a hard-bristle plastic scrub brush, give the planter a thorough cleaning inside and out. Rinse to remove all soap residue. Now, using my favorite cleaner, vinegar, wipe the entire pot with full-strength regular or apple-cider vinegar until all the white mineral deposits have dissolved. Let the pot completely dry.