Using Flame & Heat

1. Apply an open flame with a long match or lighter directly to the plastic cup.

2. Angle a magnifying glass at approximately 45 degrees between the sun and the cup. The magnifying glass when angled correctly will concentrate some of that light into a tight beam. Direct the point of the beam anywhere on the cup and the cup will begin to melt at that spot.

3. Place a plastic cup into a microwave and use the "high" setting on the microwave for several minutes. For cheaper plastic cups, the heat generated alone is enough to induce melting. For better-made plastic cups the use of a liquid is necessary. As the liquid heats up to a boiling point the cup will begin to melt from the inside out. You'll want to have the cup sitting in a bowl to catch the liquid.

Using Chemicals

1. Place some tea tree oil into a plastic cup along with some water. At higher concentrations and given a few hours the cup will begin to melt.

2. Put heavy-duty resin a plastic cup. Much like natural oils, if the concentration of chemicals in resin is high enough and you maintain prolonged exposure, a chemical reaction will take place that melts the plastic.

3. Fill up a plastic cup with gasoline and allow it to sit for a few hours. The molecules from the gasoline separate the larger molecules of polystyrene in the cup from one anothe. This in turn causes the cup to break down and melt.