Heat a pot with 2 cups of water
Add 3 tablespoons of baking soda
Stir until the baking soda dissolves
Add more baking soda until no more dissolves
Boil the solution for a few minutes
Pour the hot solution into a clean container
Let it cool undisturbed to room temperature
Chill it in the refrigerator until it becomes supercooled
Tap or scratch the surface to trigger crystallization
Watch the “hot ice” form instantly