Why does wood “crackle” on a campfire?


If you love nature, you must have experienced bonfire, right? Well, as you warm yourself, plenty of questions are likely to criss-cross your mind.

One such question is “why do wood crackle when burning?”.

Well, here is a comprehensive guide to answer your question!

Why Wood Produce Crackle Sound When Burning

The crackle sounds originate from escaping pockets of trapped steam. You are now wondering why the steam is escaping, right?

Well, when you place the wood on the fire, it’ll get hotter. The heat boils the trapped water in the wood thus turning into steam. As the heat increases continuously, the gas expands significantly and starts finding an escape route.

How the Gas Escapes

To help you understand this better, let’s first discuss the composition of the wood. Besides the water, logs are also made of cellulose.

Immediately you start heating it, the cellulose disintegrates to form more gas! When this gas combines with the steam, it exerts a lot of pressure.

As a result, there is an urgent need for the gas to escape out of the wood. So how does that happen?

It happens by creating new escaping channels! It is this process that leads to the crackling sound.

How Wood Crackling Helps in Starting Fire

When crackling starts, you’ll start observing smoke which is part of the escaping gas. When the gas mixes with oxygen, it burns to cause a flame. The more the oxygen there is, the bigger the flame will be as the reaction will be higher.

An Interesting Fact

Did you know that dump wood will make more crackling sounds than dry wood? Well, this is factual!

Wet wood has more sap/water and thus will produce more gas. As a result, you will hear more crackling sounds.

How Water Get Into the Wood

At some point, the wood was a living organism. It required water and nutrients for growth. As a result, it naturally has tiny holes to accommodate water/sap that is responsible for distributing nutrients for its growth.

To simplify this, it’s accurate to say that wood gets water from the soil through the roots.

Other ways that water can get into wood is by soaking in rainwater or through small openings made by insects on the wood’s surface.

Bottom Line

As you sit in front of a fire, you’ll likely enjoy the crackle and pop that accompanies the glamorous flames. Well, now you know where all the noise comes from!

However, you should always necessary to keep a safe distance from the flame since the escaping gas can pop and burn you slightly!