Custard Powder Explosion

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★★☆ Can be done by science teachers
Safety: ★★★ Only to be attempted with adequate safety procedures and trained staff

Categories: Combustion, Explosions

Alternative titles: Dust Explosion Demonstration

Summary

A small puff of air blows custard powder into a coffee tin where it mixes with air and ignites over a candle flame. The rapid burning of the powder produces a shockwave, demonstrating how a gas expansion can create an explosive effect.

Procedure

Make a small hole near the base of an empty coffee tin, approximately the same diameter as a short length of rubber or plastic tubing.
Insert the tubing into the hole and seal it with plasticine or Blu Tack to prevent air leaks.
Pour a small mound of custard powder into the tin so that it sits above the tubing opening.
Place a lit tea-light candle inside the tin, opposite the tubing, and prepare to replace the lid.
Once the candle is burning, secure the lid on top of the can.
Blow a short, sharp puff of air through the tubing to disperse the custard powder into the air.
Observe the ignition of the custard powder and the resulting shockwave or “fireball” inside the tin.

Links

Exploding Custard | I Didn't Know That - National Geographic:

The Exploding Custard Incident - Student Science - URNScienceShow:

Variations

Try substituting custard powder with other fine powders like flour or cornstarch to compare reaction intensity.
Vary the amount of powder to observe how fuel quantity affects the size of the explosion.

Safety Precautions

Wear safety glasses and heat-resistant gloves.
Conduct the experiment behind a safety screen or as a teacher-only demonstration.
Ensure all observers stand well back from the setup.
Do not use excessive amounts of custard powder.
Perform only in a well-ventilated area away from flammable materials.
Use a bulb or pump instead of blowing into the tube if possible.

Questions to Consider

What caused the custard powder to burn so quickly? (The fine particles dispersed in air have a large surface area, allowing rapid combustion.)
How do you know gases were produced? (The expanding gases pushed air out, creating a visible shockwave.)
Why do gases create more force than solids or liquids when heated? (Gases expand to occupy much more space.)
How is this experiment similar to the ignition of gunpowder in a firearm? (Both involve rapid gas expansion that generates pressure and movement.)
What everyday industrial safety concerns relate to this demonstration? (Dust explosions in factories handling flour, coal, or other fine powders.)