Here's the secret for how to perfectly unmold a gelatin salad: Quickly dip the mold, almost to the top, into warm--not hot--water for several seconds. Loosen an edge of the salad with the tip of a knife, then tip the mold slightly to allow air in and to break the vacuum. Rotate the mold so all sides are loose. Place a serving plate brushed lightly with water upside down on top of the mold (the water will let you move the gelatin on the plate in case it doesn't come out in the center.) Holding both the mold and the plate firmly, turn the mold upside down and shake gently. Carefully lift the mold off the gelatin. If the gelatin doesn't come out, repeat the steps.