Naphthalene charges, or, more commonly nicknamed "Nap Bombs," are used in the movie industry to simulate fiery explosions that look somewhat like a plume of burning gasoline. They do have quite an impressive effect, and surprisingly this effect is somewhat easy to duplicate, provided that one has access to the proper materials.
NOTE: The term "nap bomb" is used only because it is the common Hollywood nickname for naphthalene charges, and it is in no way meant to depict "KeWl BoMZ" or any other similar destructive devices, nor does this site advocate or depict methods for making "KeWl BoMZ" or similar devices. Anyone considering to use and/or actually using naphthalene charges as destructive devices deserves to be emasculated with a pair of laboratory forceps, impaled upon a large rotissery apparatus, and slowly nitrated in the usual mixed acids.
The first material that must be procured is Naphthalene, which is a white volatile solid, formula C10H8. It is available in the form of mothballs. Be careful when purchasing the mothballs though, as most mothballs nowadays are made of Paradichlorobenzene, which will not burn and therefore not work. Check the package; usually it will say either "Guarantee: 99% Paradichlorobenzene," or "Guarantee: 99% Naphthalene." Buy the "99% Naphthalene" type. The next nessesary material is Black Powder or Pyrodex (NOTE: Smokeless Powder will NOT work for this). Black Powder works a bit better than Pyrodex, but Pyrodex still produces satisfactory results.
First, take a parallel wound kraft paper tube (the exact dimensions are not nessesary), ram an epoxy/sawdust endplug into one end of the tube, and allow the endplug mixture to harden and cure. When the endplug has completely solidified, drill a small (~1/8") hole just above the inner end of the endplug, perhaps about 1/8" beyond the inner end. Then insert a length of Visco fuse into the hole, and seal around it with hot-melt glue. Then, fill 1/4th of the remaining space in the tube with Black Powder or Pyrodex, making sure it does not get packed or tamped. Next, mix 30% by weight of BP/Pyrodex with 70% by weight of Naphthalene by the diaper method, and fill about 3/8ths (one and a half 4ths)of the tube space with it. Next, fill the remaining 5/8ths of the cardboard tube with powdered Naphthalene (powder it in a mortar and pestle, or by coffee milling it). Now bury it in the ground until only 1" or so of the tube is sticking out of the ground. You're done! If any of this has confused you, see the below diagram.Here is a schematic of a nap bomb.