Effect:
Four or five volunteers are each given a large test tube partly filled with a clear colourless liquid. They are also given a plastic straw with which to bubble their breath through the liquid. The Wizard says "Go!" and they all begin. The solutions go milky at different rates, if at all.

What You Need:
- calcium hydroxide
- water
- large test tubes
- plastic straws

What You Do Before the Show:
- Prepare a saturated solution of calcium hydroxide (lime water) in water.
- Decant the solution off from the remaining insoluble material.
- Partially fill the test tubes about 1/3 full with the solution.
- Dilute some with different amounts of water (to give different concentrations).
- Partially fill one with water only.

What You Do During the Show:
- At random give out the test tubes and plastic straws.
- Have the contestants stand in a line faceing the audience.
- You may want to add a little dry ice to an additional test tube containing lime water.

What is Happening:
- Carbon dioxide in the breath reacts with calcium ions to form insoluble calcium carbonate (chalk).
- If a large excess of carbon dioxide is added, the calcuim carbonate goes back into solution.

Hazards:
- Lime water is mildly corrosive.
- Instruct the contestants NOT to swallow the liquid.
- Instruct the contestants to blow GENTLY so that they will not get splashed by the liquid.

Patter:
The patter used depends upon the age of the audience.
- For adults, the Wizard will demonstrate who is best at "covering up". The winner is the one who is best at giving a "white wash". The highest concentration will go milkiest first and of course the one with water won't change at all and show the loser.
- For children, a different approach is needed. If the demonstration is more "scientific", the Wizard first talks about seeing your breath on a cold day and asks what do they see. The cloud at the top of the dry ice cylinder is referred to. Some students may know that carbon dioxide is in exhaled breath. The first demonstration then is with a small amount of dry ice to show that lime water can be a test for carbon dioxide. Then invite several students to come up. You can give them all the same concentreation.