Topic summary
Ice packs
Extracted from the Wikipedia article Ice pack.
Reusable packs
Ice packs are used in coolers to keep perishable foods (especially meats, dairy products, eggs, etc.) below the 5–75 °C (41–167 °F) danger zone when outside a refrigerator or freezer, and to keep drinks pleasantly cool. The amount of ice needed varies with the amount of food, its initial temperature, the thermal insulation of the cooler, and the ambient temperature and exposure to direct sunlight. Ice initially well below freezing temperature will last a little longer.