Over the years I have observed, performed, and achieved various firecraft methods. Fire is a primary survival skill that allows us to stay warm, signal, and cook. One of these methods uses a foil gum wrapper cut into an hour-glass shape with each end touching a terminal or cap of a battery, typically a AA size. I don’t normally chew gum but I’ve found foil wrappers here and there and collect them for this purpose. Many cigarette packs have a foil seal on top of the pack that is discarded and works as well. The freshly removed foil wrapper material works best because it isn’t wrinkled. Wrinkled foil disturbs it’s resistance capability combined with delamination to the paper substrate and sometimes does not perform as well and will just get red-hot and split the foil mid-section without producing a flame.
When I acquire a foil wrapper I usually place it in my wallet, right next to the paper currency, then I’ll always have this ignitable resource should I need it when I have access to a battery. It occurred to me, why not store foil with a battery in my devices so that it is readily available when needed? Obviously it needs to be kept in a way that will not “short out” accidentally and cause the destruction of your device or an unplanned fire. For my flashlights I fold the wrapper foil-side inward on it’s self then wrap it around one of the batteries before inserting it into the handle. It can be a tight fit but is generally easy to insert and retrieve. Some compact flashlights contain a battery clip that holds three AAA batteries and the folded foil wrapper can be wrapped around it before storing inside the flashlight handle.
There are other portable electrical devices that use batteries such as cell phones, DVD players, radios, etc. that have a battery compartment in which a folded foil wrapper can be stored but exercise care when storing the foil. Be sure to fold the wrapper and position it in such a way as to prevent any shorting and may perhaps need adhesive tape to keep it in place. When initially storing your device after the foil has been installed it may be advisable to place it in or on a non-combustible surface to observe it for a few minutes and feel it for any heat to make sure that no accidental conductivity is taking place.
This video demonstrates the use of the hour-glass shaped foil strip shown above to make fire. I find that it works best to hold it vertically to create a flame.