If you want to keep the items in your cooler colder for an extended period of time, fill the cooler with blocks of ice rather than ice cubes. An ice block will not melt as quickly as ice cubes because of its density. You can purchase block ice at businesses such as grocery or convenience stores or a fishing supply shop, but it is much more cost effective to make your own ice blocks at home.
Things You'll Need
Plastic or metal pans
Measure the approximate dimensions of the inside of your freezer with a measuring tape. The purpose of this step is to check how large of a pan of water will fit in your freezer. For example, you can fit a rectangular pan that is at least 17 inches long by 15 inches wide and 9 inches tall in a refrigerator/freezer 18 cubic feet in size. If you have a top loading, stand-alone freezer, this step is less relevant as you have significantly more room to make block ice.
Check the dimensions of your cooler to be sure the ice block will fit.
Purchase a metal or plastic pan sized to the appropriate dimensions if you do not already own that size of pan. You can use metal cake pans or -- if your freezer and cooler are sufficiently large -- plastic dishwashing pans.
Clean the pan with soap and water before using it.
Fill the pan with water so it is about 90 percent full and place it on a counter or table adjacent to the freezer. Water will expand when it freezes so you need to leave some room at the top of the pan.
Place the pan in the freezer. Do this slowly in order to not spill any water. Make sure the pan is sitting on a flat surface.
Wait at least 12 hours for the ice block to form. This time will vary depending on the model and temperature of your freezer and the size of ice block you are making.
Take the pan out of the freezer when the water has completely turned to ice. There should be no movement of water in the pan.
Slap the pan on the inside of your cooler to break the ice free from the pan. You may need to do this several times before the ice falls into the bottom of the cooler.
Although you can purchase block ice makers or ice molds at retail stores or on the Internet, this will increase your cost of making ice.
You can make multiple ice blocks at once by using slightly different sized pans and stacking them in the freezer. Place a piece of waxed paper in between each pan.