We got this really fun book from Costco a few months ago, the kids and I pull it out occasionally and do crafty things together. Emma was completely enamored with the idea of a cauldron boiling over.
We had to do it three times, each with a different color.
Here's the pics - for dramatic effect.
To do it yourself - find a good bowl, and something to catch the excess.
About a cup of vinegar mixed with a few drops of food coloring and a good squirt of dish soap. Put about two spoonfuls of Baking Soda in the bowl and then add your vinegar - after your kids say the magic words...
Hopefully you're not after more specific measurements - I cook this way too.
