Helpful Hints from joeeze: How to make clear(er) ice at home

"Water from the tap contains dissolved gases and some minerals. These separate from the water as it freezes and get trapped in the ice as bubbles and sediment, which looks milky. Commercial ice is made from treated water and in a machine that washes away gas and sediment as they're expelled from the freezing surface. You can make clearer ice at home with distilled water that you've boiled to expel dissolved air."

[via Harold McGee and the New York Times]