This article is from the Scouting FAQ, by Bill Nelson firstname.lastname@example.org, Soaring Golden Eagle email@example.com and Alan Houser firstname.lastname@example.org with numerous contributions by others.
5. Magic balloon.
Materials: large balloon (at least 8 inches in diameter when inflated),
Setup: small piece of dry ice inserted into balloon.
Effect: balloon continues to inflate, even after being tied closed.
Scenario: Balloon is partially inflated at the beginning of the meeting
and tied. By the end of the meeting, the balloon has become even more
How it's done: the dry ice inside the balloon slowly vaporizes when
added to warm air. Partially blowing up the balloon provides enough
warm air for the process to occur.
6. Magic water test.
Setup: Styrofoam or paper cup (not plastic!) with slush powder
("Aqua-gel", "Joke-gel") in bottom of cup. Approx. 1 teaspoon of powder
per 4 ounces of water. Slush powder is available at magic supply stores
and novelty shops (usually in the gag gift section with the pepper gum,
plastic vomit, etc.)
Effect: water is poured into a cup and then inverted over the boys'
heads without spilling.
Scenario: Final test for boys advancing in rank. Pour water (I use
water colored with blue food coloring) into the glass and tell the boys
that if they are ready to advance in rank, then the spirit of scouting
will protect them in this final test. Turn the cup upside down over the
Variations: have parents hold small cups with gelled water over each
boy and have the boys stick a straight pin through the bottom of the
cup. Be sure that the cups are held above the sight of the parents as
well so that they cannot see the gelled liquid inside.
How it's done: The slush powder causes the water to gel on contact and
will not pour/leak from the glass.