Boiling Water in a Paper Cup Experiment

Everyone knows that paper is very burnable. Hold a paper cup over a flame to see for yourself. But what about if we fill it with water? Will the paper still catch on fire? Or will the water heat up and boil? This post describes an experiment you can do to answer these questions.


  • Protective goggles
  • Gas burner
  • Matches
  • Fire-safe tongs
  • Water
  • Uncoated paper cups


  1. Put on the protective goggles
  2. Fill a muffin cup nearly to the brim with water
  3. Turn the burner on medium heat
  4. Using tongs, hold the cup about six inches above the burner
  5. Observe waht happens to the cup and the water
  6. What temperature did the paper heat to in the course of the experiment?

Practical tips

Make sure to keep enough distance between the cup and the burner to avoid the flame climbing up along the edges of the cup.

Also, make sure to use a cup that doesn’t have a thick wax coat.

What happens?

The water inside the paper cup will cool the paper to 100°C. Liquid water cannot reach a temperature above 100°C, and the paper cup will also hold this temperature. The paper thus doesn’t get a high enough temperature to catch on fire. All the energy from the flames is spent on evaporating the water.

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