Odds are that you've seen a demonstration of this stuff before, most likely in your high school chemistry class. It is a highly sensitive contact explosive made from two ingredients ammonia and iodine crystals. It is so sensitive when dry it can be set off by a feather or even a fly. The last time I made this was years ago for a science project. It was the middle of winter and I had been setting off batches of this stuff in my backyard all day. When night fell it started lightly snowing, the snow flakes fell to the ground and set off minute traces of the NI3. The resulting snaps were loud enough to wake up my mom who then woke me up and told me to do something about it. I wasnt really sure what to do about it so I filled up a bucket of water and threw it out over the pavement, setting off hundreds of little snaps which each gave off tiny poofs of purple smoke.
It has got to be one of the most surreal memories I have, being out in the moonlight while snowflakes gently floated down, causing the dead silence to be broken by little purple snaps going off everywhere.
Heres the wiki for it nitrogen triiodide
Step 1: Materials
Can be bought on e-bay, unitednuclear.com, or http://shop.armorforensics.com/mm5/merchant.mvc?Screen=PROD&Store_Code=RedWop&Product_Code=1-2805&Category_Code=
That last one is a forensics website. Iodine crystals are used in a fingerprint lifting process called iodine fuming. As you can see on the label on the jar, the gas from the crystals has stained the paper to a dark purple color. Iodine gas is toxic, so do this experiment in a well ventilated area.
The purer the better. I use clear ammonia available almost anywhere. The store bought stuff is actually Ammonium hydroxide, meaning that it is ammonia dissolved in a ton of water. If for some reason you have access to highly concentrated ammonia the resulting nitrogen triiodide will be much more powerful, and therefore handled much more carefully.
A tupperware container