You can make clear ice cubes in a cooler by using directional freezing, which allows impurities and air to freeze last, resulting in clear ice.
Here's the process:
- Fill a Small Cooler: Use a small cooler and fill it with approximately 5-6 inches of water. It's best to use filtered water for even clearer ice, but tap water will also work.
- Place in Freezer: Put the cooler without the lid into your freezer. Make sure it's on a level surface.
- Wait for Partial Freezing: Allow the water to freeze for 20-24 hours. The water will freeze from the top down. You'll notice a block of ice forming at the top, leaving unfrozen water at the bottom. The ideal thickness of the ice block is about 3-4 inches. This timeframe may vary depending on your freezer's temperature, so check periodically.
- Remove Unfrozen Water: Carefully remove the cooler from the freezer. You'll see that the water at the bottom is still liquid. This liquid contains the impurities and dissolved air. Pour this water out.
- Extract the Ice: Invert the cooler to remove the large block of ice. You might need to run a little warm water on the outside of the cooler to loosen the ice block.
- Cut into Cubes: Use a serrated knife and a mallet or ice pick to cut the large block of ice into smaller, cube-sized pieces.
- Store the Ice: Store the clear ice cubes in a freezer bag in your freezer until you're ready to use them.
Why does this work?
This method, called directional freezing, forces the water to freeze from the top down. Impurities and dissolved air are pushed downward as the ice forms. Because the cooler insulates the water, it freezes very slowly, allowing time for these impurities to concentrate in the remaining unfrozen water. By removing the unfrozen water, you remove the impurities, leaving you with clear ice.
