We all know what elephant toothpaste is, but what's the best way to make this massive growing foam? Dr. Lithium from NurdRage has answers. He'll show you the best way to reproduce this chemical reaction to get the best foaming action! This is a classic science class demonstration.
Warning: hydrogen peroxide causes burns, wear gloves.
The procedure is very simple. First mix 50mL of detergent with 100mL of 30% hydrogen peroxide. Then add in 10mL of a saturated solution of potassium iodide. The mixture will then produce a massive foam.
A variation is to also add 5g of starch to the peroxide mixture. When it foams, the foam will have light and dark patches due to the uneven reaction of starch and triodide that forms.
Yeast can be used in place of iodide for a slower reaction, but this also allows you to add fluorescent dye to the mixture to make a "glowing elephant toothpaste" when you shine ultraviolet light on it.
In all of these experiments, what's happening is the hydrogen peroxide is being catalytically decomposed into water and oxygen by the iodide or the yeast. This creates bubbles of oxygen that then foam up due to the detergent.