When the lights go out, most people gravitate towards flashlights or candles. If you do not have access to these items, however, you are going to have to rely on the acclimation of your eyes to the darkness. You will be able to see surprisingly well in the dark, but still not as well as normal, or as well as you would be able to with a light source. Having the ability to create light in darkness with everyday food items can come in quite handy, especially if you need to read some instructions or a manual and it cannot wait for sunrise.
The first method of candle making with food items is to use a citrus fruit with a thick peel. This can be an orange, grapefruit, or even a lemon, but due to the bump on the ends of a lemon, you will need to make arrangements to safely prop it up. Cut your fruit in half in the center so that the slices are positioned vertically. Pull it apart and remove the contents (eat them if you wish!) but be careful not to remove the center fibers that reach from the top to bottom of the fruit as this will act as a wick. Your goal is to create a bowl out of the fruit peel with a fibrous wick in the center. Pour vegetable oil or olive oil into your peel bowl and light the wick. Your fruit candle should last for several hours.
Another option for a survival candle is to make one with Crisco. A shortening made from a semi-solid vegetable oil, Crisco comes in a metal can. To make a Crisco candle, it is best to have a candle wick, but if you do not, then any sort of twine that is slow burning should work. In order to make a candle with Crisco, you need to sink your wick in the center of the candle. A candle wick has a small metal disc on the bottom, so if you are using twine you want to improvise something similar, such as tying your twine around a small pebble. With a stick, guide your wick down into the center of the Crisco can. You want to get it all the way to the bottom for maximum burn time. Once you are certain that your wick base is at the bottom, tap the can on a hard surface a few times to settle any of the semi-solid shortening back in place. Light your wick (or makeshift wick) and enjoy hours and hours of light as your Crisco slowly melts much like the wax of a normal candle would.
Butter can also be used to create a light source. Take a stick of butter and cut in in half while it is still in the wax wrapper. Stand your butter upright so that the exposed butter is facing up with the wrapped end facing down. Into the center of the butter, insert a wick or makeshift wick. This can be a piece of twine or even paper. Use something along the lines of a toothpick or paperclip to push your wick down into the center of the butter all the way down to the bottom. Take the excess wick that is sticking out and smear a small amount of butter on it to encourage it to burn and then light it. You should be able to get a couple hours worth of light out of your butter, but be warned that melted butter can be messy, so place it on a surface that will not be affected by melted butter and is also not flammable.
Food items are best consumed, but during tough times they can be adapted to serve other purposes. Keep an open mind and give these candles a try if you find yourself in a tight spot where one might be able to help you out. Considering that a tub of Crisco costs around $4.50, you might want to make that a preferential purchase to a standard candle. It will burn longer for less money and you will not be at risk sitting in the dark.