Filming Small Explosions with a Camera

 

Filming Small Explosions with a Camera

Protecting Your Kit While Capturing the Science

Filming small explosions — flash reactions, gun cotton, hydrogen balloons, pressure releases — can produce stunning visuals that genuinely help students see chemistry and physics in action.

But while we obsess over human safety (rightly), it’s easy to forget that cameras, lenses, microphones, and lighting rigs are also sitting right in the danger zone.

And camera repairs are not covered by the CLEAPSS handbook.

What Counts as a “Small Explosion”?

In an educational context, we’re usually talking about:

• Flash reactions (e.g. gun cotton, lycopodium powder)

• Rapid gas expansion

• Small combustion demonstrations

• Contained pressure releases

Short duration. Low mass. High visual impact.

Still more than enough to:

• Pepper a lens with debris

• Crack a filter

• Cook a sensor with heat or IR

• Kill an exposed microphone

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🔒 Camera Safety: Lessons Learned the Hard Way

1. Distance Is Your Cheapest Insurance

Even doubling the distance massively reduces:

• Heat exposure

• Overpressure

• Debris impact

Use:

• Longer focal lengths

• Cropped sensors

• Post-production framing

If it looks “too far away” on set, it’s usually perfect in edit.

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2. Sacrificial Filters Are Not Optional

A £15 UV or clear filter:

• Takes the hit from debris

• Protects the front element

• Is far cheaper than replacing glass

Consider stacking:

• Clear filter (impact)

• IR-cut filter (heat & sensor protection)

If it shatters, you’ve won.

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3. Shield the Camera, Not the Experiment

Perspex, polycarbonate, or even thick acrylic sheet:

• Stops fragments

• Survives heat

• Lets you keep a clear view

Important:
➡️ Angle the shield, don’t mount it flat. Reflections and shockwaves behave badly off flat surfaces.

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4. Heat and Infrared Are Silent Killers

Explosions don’t just throw bits — they emit:

• Intense IR

• Localised thermal spikes

Solutions:

• IR-cut filters

• Avoid wide-open apertures

• Keep sensors cool between takes

This matters especially with mirrorless cameras.

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5. Remote Everything

If the camera can be triggered remotely, do it:

• Remote record

• Wireless monitoring

• Pre-focused manual setups

Bonus: it also makes students take safety more seriously when nobody is near the kit.

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6. Audio Is Expendable

Mics are fragile.

• Use cheap lavs or boundary mics

• Keep primary audio well back

• Expect to replace windshields

Explosions are visual teaching moments — audio is secondary.

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🎓 Why This Matters Educationally

High-speed or slow-motion explosion footage:

• Turns abstract theory into observable reality

• Improves recall and engagement

• Lets students replay what the human eye misses

But modelling professional safety practice is part of the lesson.

Students don’t just learn chemistry or physics — they learn how scientists work responsibly.

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🧪 Final Thought

If your camera setup feels slightly over-protected, you’ve probably got it right.

If it feels excitingly close… it’s already too close.