TO MAKE YOUR OWN HAND WARMER YOU WILL NEED:
2 sealable plastic bags (approximately 4 inches square)
1/2 ounce (14 grams) powdered lime (calcium oxide)
2 tsp. (10 cc's) of tap water
a plastic pipette or eye dropper
a bucket of cold water
Before you try the following experiment, make sure that you are wearing protective glasses and latex or rubber gloves. Do NOT handle these chemicals with your bare hands. Don't use a nylon apron or gloves.
NOTE: Be careful! When mixing the contents you may find they become so hot that they can cause serious burns.
Take a small, self-sealing plastic bag and put it inside another bag of the same type and size. Using the teaspoon, carefully add the half ounce (14 grams) of powdered lime to the inner bag, and use the pipette or eye-dropper to add about 2 teaspoons (10 cc's) of tap water. Seal both bags securely, and mix the contents together by carefully manipulating the powder and the water with your fingers. After a few seconds, you will notice that the temperature of the hand warmer starts to rise dramatically.
When we took our slaked-lime hand warmers to the rest of the team on the Franz Josef Glacier, we found that so much heat was generated that some of the plastic bags actually melted. If this happens when you try the experiment, drop the bags into a bucket of cold water and dispose of the resulting solution by flushing it down the toilet. Be sure to wash your hands immediately and thoroughly in lots of cold running water.