# How a Firecracker Works

How a firecracker turns one small spark into a flash and a bang, from its bamboo origins to the powder, fuse and paper tube that contain the pressure\.

By quiet\-moon\-3b6b0485

Topic: Physics & Chemistry

[Open the interactive Jig](https://ask.jig.com/j/qJSFeZ2CQHyH)

## Transcript

### 1. A paper tube that goes bang

This red firecracker is shown much bigger than life: a real one is only a few centimetres long\. It turns one tiny spark into a flash and a bang\. Let's look inside to find out how\.

Drag anywhere to turn the scene\.

### 2. It started with bamboo

More than 2,000 years ago in China, people tossed green bamboo onto fires\. Each hollow section between the joints is sealed, so the trapped air and sap heated up, pushed hard and burst the stalk with a loud pop\.

Much later, gunpowder was packed into tubes of bamboo and then rolled paper\.

### 3. Look inside

Here the firecracker is cut in half, in a simplified drawing\. A thick wall of tightly rolled paper surrounds a small pocket of powder\. Hard plugs seal both ends, and the fuse pokes into the powder from the top\.

### 4. A powder that brings its own air

Most fires need oxygen from the air around them\. This powder is a mix of fuel and an ingredient that gives off oxygen when it gets hot\. Because the powder carries everything it needs, it can burn very fast even when sealed inside a tube\.

This explains the idea only\. Making or taking apart fireworks is dangerous: leave it to trained experts\.

### 5. The fuse: a slow, steady spark

The fuse is a cord with a thin line of powder inside, wrapped so it burns slowly and evenly\. That delay gives the person who lit it time to step well away\. Light the fuse and watch the spark creep down toward the powder\.

### 6. From solid to gas in a blink

When the spark reaches the powder, the powder burns all at once and turns into a huge amount of very hot gas\. That gas needs far, far more room than the solid powder did\. The tight paper tube has nowhere to put it, so the pressure inside climbs\.

Slow motion: in real life this happens in a tiny fraction of a second\.

### 7. Pop\! The push becomes a bang

The paper finally tears, and the hot gas bursts out and shoves the air around it\. That push spreads outwards as a pressure wave, which our ears hear as a bang\. The flash arrives first, because light is much faster than sound\.

Sound travels about 343 metres every second\. Loose powder in the open only fizzes: the tight tube makes the bang\.

### 8. Celebrate with care

Strings of red firecrackers welcome the Lunar New Year: an old legend says their noise scares away a monster called Nian\. Up close, the bang is loud enough to hurt ears in an instant, so watch from far away and cover your ears\. Only adults should light them, and never touch one that didn't go off\.