Effect:
An orange powder is in a mound. It is ignited and the lights are turned out. The audience sees an erupting volcano. When it stops and the lights are turned on, there is a much larger dark green mound.

What You Need:
Ammonium dichromate
Acetone
Heat resistant pad
Matches

What You Do Before the Show:
- Measure out about 50 mL of ammonium dichromate.
- Pour onto a mound on the pad

What You Do During the Show:
- place a few drops of acetone onto the top of the mound
- ignite
- turn out the light

What is Happening:
The orange ammonium dichromate is converted to green chromium oxide.

Hazards:
- Fire, the heat resistant pad must also not burn.

Patter:
Your call.