Adventist Youth Honors Answer Book/Camping/Keeping food cool

The most effective way to keep camp food cool on a campout is by storing it in a cooler with ice. Use blocks of ice rather than ice cubes or crushed ice, as it will remain frozen far longer. Solid blocks of ice should easily last for three days. You can buy it at a store or make it ahead of time by freezing water in plastic gallon or half-gallon jugs. You do not need to remove the ice from the jugs. To extend the life of the ice, make sure the cooler's lid is closed all the way and tight-fitting, and do not leave it open any longer than necessary.

One way to keep food cool without ice while on a camping trip is to place the food in a water-proof container, place that in a mesh bag and secure it in a stream or brook. Another way is to put the food in a bag, cover it with several layers of burlap, wet the burlap, and suspend it from a tree branch. As the water evaporates from the burlap, it will cool the food. You have to re-wet the bag occasionally.