This is a fantastic stunt that you just have to try. It's essentially a Science experiment about acids and alkalis but I think it's more like a spectacular party trick. It takes five minutes or so to set up but it's very simple and I can guarantee, the results are well worth it!

You Need:

Three glasses

Red cabbage

Bicarb soda

White vinegar

Hot water in a bowl

Secret Preparation:

1) Put a teaspoon of bicarb soda into the first glass and fill to near the top with water. When it has dissolved it should look colourless.

2) Chop up a handful of slivers of red cabbage. Soak them in hot water for about five minutes until you have a purple liquid. Strain this into a second glass.

3) Fill the third glass to the top with vinegar. Of course, it'll look colourless.

To Perform:

To begin with, keep the glasses out of sight. Begin your spiel like this.

Once upon a time, the Emperor Julius Caesar invited his friends Brutus and Antony around for morning tea. "Let's have a drink," said Caesar. "Here's some water for you, Brutus!  (Produce glass 1 and place it to the left)

"And here's some water for you, Antony."   (Produce glass 3 and place it to the right.)

"And I'll have some blackcurrant juice"   (Produce glass 2 with the purple cabbage liquid and place in centre)

Brutus said, "Oi! Why have you got blackcurrant juice while we have to make do with water? I don't want water! I want blueberry juice!" Said Caesar, "Alright, then you shall have some."   (Pour some purple juice from glass 2 into glass 1. The 'water' will magically turn blue)

Antony said, "I don't want water either. I want strawberry juice!" Then you shall have some," said Caesar"   (Pour some of the purple juice from glass 2 into glass 3. That 'water' will magically turn red.)

Brutus said, "Actually, I think I'd prefer strawberry juice as well." Caesar said, "No problem"    (Pour some of the red glass 3 into glass 1. It will turn red too.)

"In fact," said Caesar, "I think I'd prefer strawberry juice too."   (Pour some of the red glass 3 into glass 2. Now all the glasses will be red)

What happened?

Pouring into the first 2 glasses is easily explained. Red cabbage juice turns red with acid and blue with alkali. When you poured the strong acid (vinegar) from glass 3 into the weak alkali of glass 1 (bicarb soda) you overwhelmed it. So the solution became mostly acid and turned red. The same happened with the strong acid and the indicator in glass 3.