Pre-freezing these bowls will keep your food cold for 8 hours at ambient temperature. The outer air chamber prevents the bowl from creating condensation while keeping the inner chamber gel frozen. In test results, a bowl was put in the freezer until the gel was frozen. 35 degreesF, potato salad was placed in the bowl without a lid and stirred every 30 minutes. After 8 hours the potato salad was at 38 degrees F. Great product for your next picnic or party requiring no ice to keep your food cold. When your cold wave bowl is filled with food, you may have to occasionally stir the contents to prevent freezing the food. Always add food that is pre-chilled to proper temperatures.