Much simpler: Put a little dry ice in a plastic drink bottle, like bottle
water comes in.

Add an inch or so of water. Cap tightly. Run away!

The 1/2 liter bottle will swell up to the size of a football before
exploding with a bang reminiscent of shotgun blast...very loud. Sometimes
it takes a few minutes, sometimes longer. If you don't use enough dry ice,
it only swells. Don't touch it, it could still blow. Throw a rock at it
first, or just leave it alone..

jak

"Stepan Novotill" wrote in message
...
The following can be fun too: Fill a vessel up with salt water. throw
in two carbon rods connected to a car battery charger.
Run it a while till most of the chlorine has gone out.
Power off, put on a lid, hide behind a wall, power on and run the
generated gass into a SMALL baloon. Power off when 5" diameter.
Use a light plastic lid that will pop off and not hurt anyone if the
gas in the vessel ignites.

Then hold the baloon at arms length, close your eyes and take a match
to it. Do it with your hair wet, in wet smim trunks next to a swimming
pool so you can jump in if you catch fire. We had great fun with this
as kids. It is not unbearably loud but generates an incredible bang
and you feel a heat pulse similar to what you get when you set off a
large photoflash right against your skin.