Dry ice can keep your ice and frozen goods for many days. Heading for the wilderness or far away from civilization where your supplies need to last for a longer time – dry ice gives more than twice the cooling energy per pound of weight and three times the cooling energy per volume than regular water ice.
USING DRY ICE
Plan on using 5 to 10 pounds of dry ice per day, depending upon the ice chest size. Dry ice will keep everything frozen in this ice chest, including extra ice, so consider refrigerating non-frozen goods with regular ice in a separate ice chest. Dry ice sometimes comes in 10-inch squares, 2 inches thick, weighing about 10 pounds each square. Plan to put one square per 15 inches of ice chest length. For a forty-quart cooler, use two squares or 20 pounds. If you can only get pellets, separate them into 10-pound paper bags to spread them around and keep them from falling to the bottom. Do not seal plastic bags tight, or they will burst. At -109°F or -78°C, dry ice will freeze and keep everything frozen in its container until it is gone. These frozen items will take extra time to thaw because they have been so cold.
HOW TO PACK DRY ICE
Place the dry ice on top of the food as cold sinks. When packing items in the container, fill all the space. “Dead air space” will cause the dry ice to sublimate faster. The best storage container is a three-inch thick urethane insulated container like those used to ship frozen goods. Lining the inside of your ice chest with sheets of Styrofoam could increase the life of dry ice. Dry ice sublimation (changing from a solid to a gas) will vary depending on the temperature, air pressure, and insulation thickness. The more dry ice you have stored in the container, the longer it will last.
OUTFITTER’S SECRET Jenifer Trout of Pittsburgh, PA, explains John Judson of the QuarterCircle-Circle Ranch’s secret: My family went with an outfitter on a horse packing trip in Colorado during the summer. On the second night in the wilderness, John lamented that our menu was screwed up because the ice cream was “too frozen.” He pulled it out of the cooler and bounced it on a wood slab. It was a brick! He’d brought the food in 2 small coolers, which doubled as stools. One was for refrigerated food, and the other was for frozen food. He’d move some food (predominantly meat) from the frozen cooler to the refrigerated cooler each day. He used no wet ice or ice packs at all. We had ice cream on our third night out – after it had thawed to an appropriate temperature in the refrigerated cooler. His trick was a block of dry ice wrapped in newspaper – and it worked unbelievably well!
FROZEN LETTUCE When camping, my wife and I had too many leftovers to keep in our regular ice chest. So we put the salad in our freezer ice chest. The dry ice was only 15 pounds at the beginning of the trip on the bottom of the ice chest, and extra ice was on top of it, and then the salad was at the very top. We thought that the ice would be plenty of insulation, but we had an authentic crispy salad the following day. An actual ice lettuce salad!
HOW TO KEEP ICE FOR WEEKS A camper reports: “I have a 100-quart Coleman that I pack before leaving with a 50-pound block of dry ice and two 25-pound blocks of regular ice on either side of the dry ice. I wrap the dry ice in many layers of newspaper as an excellent insulator. If the cooler is kept in the shade and covered with a heavy blanket, the dry ice will last from 8-10 days, at which time the wet ice first begins to melt. The cooler will then last another 4-5 days. I would bet that using another method I heard (burying the ice chest in sand) in conjunction with mine would keep the wet ice available for 2-3 weeks. However, there is a downside. (1) Keep only frozen foods in the cooler until the dry ice is gone (no beer). (2) Lots of weight — the whole shebang weighs 100 lbs. sans food. Dry ice is very dense – a 50 lb. block is the same size as a 25 lb. block of wet ice.”