A big ice block in the middle of your punch bowl can be as impressive-looking as it is functional. They're perfect for parties as they melt more slowly than individual cubes, cooling the punch while only gradually diluting. For a flawless block, be sure to consider:
Shape: Try a sphere for a round punch bowl. Circular Tupperware makes a great mold. Remember, ice expands—don’t fill the mold to the rim.
Size: Your ice block should be about half the size of the bowl--you need space to dip the ladle.
Prep: Larger ice blocks can take up to 48 hours to freeze thoroughly, so plan accordingly.
Flavor: If your area has funky tap water, use spring or distilled water.
Appearance: For clearer ice, boil the water before freezing. And to add a decorative touch, add small edible flowers, mint, or basil leaves to the water before freezing.