My friend calls them flint bombs but they are more like some type of sparkler as they don't blow up anything. These devices are only the left over flint from a disposable butane lighter which will not do anything at room temperature. However, if you heat flint to the point of incandescence (glowing temperature) and then throw them against a solid surface, they will break up into a shower of sparks. Making one is very simple.
Still however, know that these devices may start fires or cause burns. Do not throw these towards flammable objects, objects that can be damaged by heat or sparks, or near people. A large area should be used to set off these flint bombs and should have no flammable objects within a 20 foot radius. Out in the street is the best if there are no parked cars nearby. Avoid concrete as the sparks may leave a permanent scorch mark.
Remember I will not be liable if you cause a fire, burn down someone's house, set the Christmas tree on fire, blind someone, burn your pets, ignite your hidden stash of illegal fireworks, burn your friend, burn yourself, damage your neighbors' Lexus, blow a urinal off the wall, blow the door out of your garage, scorch the lawn, break a gas pipe, or cause any other physical or property damage regarding these devices. I expect users of this information to at least have some common sense as potato cannons are not blasting helpless little spuds through any of the windows in my home and god knows how many web sites there are that show you how to construct these
You will need:
>One empty butane lighter
>Another lighter that works or
you can use a candle.
>A street outside to throw the hot flint
Pry the metal top off the empty lighter with the pliers or you can just use your hand if you have sharp fingernails. Remove the sparkwheel by prying it off. Be careful as the flint has a spring underneath that will pop out and cause both to fly into the corner of the room where you can't find it. It is recommended you take the lighter apart in the bag. The flint is a small black thing that looks like a pencil lead
Take the spring from the lighter and stretch it out a few inches. Wrap it around the flint to make a handle so you can hold the flint while heating. If you lost the spring, you are still fine. Just use a wire twist tie instead.
Go outside at night and find a safe place to throw the flint once you heat it. Out in the street is the best. Make sure there are no parked cars nearby or any thing else that can be damaged by the sparks or catch fire. Hold the spring or wire with one hand and use another lighter ( A jet flame lighter or micro torch works best) or a candle to heat the flint until it is glowing bright orange.
When the flint is fully heated, remove it from the flame and quickly before it cools, throw the wire with the flint on it against the street. When it hits the ground, BANG! You will see a bright flash, lots of sparks and hear a fizzling sound. Also if you did this indoors, you'll find your mother yelling at you for burning holes in the carpet!
Other ways you may set a flint bomb off is to flick the heated flint away from you with your thumb or index finger or heat the flint while it is sitting on the ground then kick it out into the street.
Pictures are taken from Matchrockets.com. Used without permission