If you are a purist like me, you pursue perfection. While that was my primary motivation for experimenting with clear ice, there are reasons why it should matter to you as well.
Cloudy ice comes from impurities in the water. Normally, these impurities are dissolved into the water in its liquid form and are invisible to the naked eye. When ice freezes, these impurities separate themselves from the liquid and become visible.
Impurities normally found in tap water – such as chlorine, pipe rust or plastic, dust, and fluoride can negatively impact the taste of your ice and ultimately your whiskey. Do you really want to ice that tastes like bleach and rusty pennies to your bourbon? Thought not.
Since some of these impurities come from the air itself (dust), you wont be able to get rid of them all. However, there are two options that you can choose to come close:
1. Boil the water first: You will be able to get significantly clearer spheres of ice if you boil tap water before freezing it. Pour the water into the mold while it is still hot. The slower the freeze, the clearer the ice. Let your molds sit in the freezer longer than the recommended time of 6 hours and you should be good to go.
2. Use distilled water: Using distilled water not only minimizes the numbers of impurities in your ice sphere, it also ensures that you taste nothing but your bourbon as your perfectly clear ice sphere slowly melts.