Crystal clear ice can be made easily and cheaply with a method called ‘directional freezing’. This method was written about back in December of 2009 by Camper English from Alcademics.com – read his article ‘Clear Ice Blocks at Home in an Igloo Cooler‘ for a more in-depth look as well as some other interesting experiments.
Directional freezing is the act of freezing a liquid from top to bottom. This method forces the impurities and air bubbles downwards due to the insulated materials on the bottom and sides. Follow the steps below or skip to the bottom to watch the step by step video.
Step by Step
Fill your cooler with water (filtered is preferred) and leave in the freezer for approx. 24 hours (depending on the size of your cooler). Don’t forget to leave the lid off when freezing.
When removing the cooler the following day, the bottom few inches will most likely still be in liquid form so this will be need to be drained – this can be done when removing the ice block or by a drain at the bottom of your cooler. You will need to drill the hole prior to freezing and use a bung to stop the water from leaking. Remember that it will need to be a solid bung that will retain the insulation otherwise it will freeze from the bottom (which you do not want).
Let the cooler rest for 30-60 minutes before upturning. The ice should slide out relatively easy, leaving a crystal clear block.
Use a serrated knife to score the ice before using a mallet and pick to chisel into smaller pieces.
Try making long rectangles for collins glasses and large cubes for Old Fashioneds & Negronis. If you are feeling adventurous, test your skills (and patience) by hand carving a sphere.