Serving cold, frozen ice cream is possible at a summer picnic, but you'll need more than a standard cooler and a few bags of ice. Manufacturers keep ice cream frozen during shipping with storage unit temperatures between -22 and -40 degrees Fahrenheit. Ice cream remains solidly frozen indefinitely in temperatures below -13 degrees Fahrenheit. However, air temperatures above this point will cause ice crystals or melting. Lining a cooler with a few bags of ice is not cold enough to keep ice cream frozen; you'll need dry ice. Dry ice is at least -109 degrees Fahrenheit and can keep your keep your ice cream frozen solid for up to 24 hours with proper packaging.
Protect your hands with oven mitts or leather gloves before handling or packing the dry ice into a plastic non-airtight beach cooler or ice chest. Dry ice emits carbon dioxide during evaporation which will force an airtight container to expand or explode.
Place one 10-pound block of dry ice under the ice cream and the other block on top of the ice cream for maximum coldness. You'll need a minimum of two 10-pound blocks of dry ice to adequately cool a 40 quart cooler for 24 hours.
Line the cooler with any additional foods you want frozen, including bags of loose ice. Do not add refrigerated items, like cold-cuts or fruit, in your dry ice cooler or they will freeze.
Stuff crumpled newspaper wads into the unoccupied cooler space. Empty air space increases the evaporation rate of dry ice, resulting in a warmer cooler.
Secure the lid and store the cooler in the back of your vehicle. Increase the longevity of your dry ice by wrapping the cooler in old towels or sleeping bags. You can also add additional blocks of dry ice to the cooler if enough room remains.
Purchase your dry ice as close to picnic time as possible for maximum longevity.
Keep the windows open while transporting dry ice. Dry ice releases carbon dioxide which can cause respiratory distress in an unventilated environment.