Materials

Calcium chloride ice-melt pelletsWaterTwo ziploc bags of different sizes

Instructions

  1. Fill a large ziplock bag one quarter of the way full with calcium chloride ice-melt pellets (available at most hardware stores).
  2. Fill a smaller ziplock bag halfway with water, close tight, and place inside the first bag.
  3. Squeeze the smaller bag until it breaks open, to create a heat-producing reaction that will last 20 to 60 minutes. Originally posted by Justin DiPlacido on Instructables.