Pre-Cooling: Coolers are designed for maximum thermal retention. They will retain heat as well as cold. If you store a cooler in a warm spot, heat will be absorbed and retained. Store your cooler in a cool environment. To imporve performance, pre-cool the cooler with a bag of ice overnight before loading contents.
Start with Chilled Contents: Whenever possible, chill or freeze goods prior to packing them into the cooler.
Size of Ice is Key: Block ice melts at a slower rate than small pieces. Small pieces of ice will chill contents faster, so for optimum cooling and ice retention both sizes should be used.
More Ice is Best: Fill your cooler with as much ice as possible, typically twice the amount of ice to stored goods is recommened. More ice limits the amount of air inside the cooler, and less air means longer ice retention.
Keep It Cold: As ice melts, cold water takes its place. The cold water keeps the air out and works as an insulator. Leave the water in unless you are replacing it with ice. Open the lid as few times as possible to limit the amount of cold air that escapes.
