You would need equal amounts of Ammonium nitrate and water to make ice without the use of a freezer or ice maker. An ice maker uses freon and water to make ice, that concept may work if you can find a way to circulate the freon around a metal object to make the ice without the use of electricity.
In order to make ice with this method, the following items are needed:
A Bucket or Large Pot
A Smaller Metal Bowl
Measuring Containers – At least two of these.
Mixing the coolant for making the ice:
Mix equal parts of ammonium nitrate and water in the bucket. Fill the bucket 3/4 of the way full with the mixture. Place a smaller metal bowl on top of the rim of the bucket or large pot. Fill the smaller metal bowl half full of water. It will take several hours for the water to freeze into ice.
In an emergency having the ability to make ice could be crucial. If you are a diabetic in need of insulin imagine how hard it would be to keep your insulin cold. This could work well if you had enough ammonium nitrate on hand or a way to circulate water through the mixture.