Firewood Pops

Why Firewood Pops And Crackles (And How To Get More Or Less Of It)

In Firewood by James O'KellyLeave a Comment

A fire that pops and crackles can be part of a pleasant fireplace experience and ambience, but in some cases it may be occurring too much or you may simply want to hear more of these traditional fireplaces noises.

The amount of popping and crackling in your fires can be a result of the type of wood you’re burning, so why does firewood pop and crackle?

The sound of firewood popping and crackling are the noises made by gases escaping quickly when the firewood is being burnt. The amount of pops and crackles produced by a fire can depend on the type of wood, the moisture content of the wood and the efficiency of the combustion.

To find out more about why fires pop and crackle and which types of wood you should be choosing to help your fires pop and crackle more or less, keep reading on.

Why Does Firewood Pop And Crackle?

The noises created by fireplaces can be a very relaxing experience, but these traditional fireplace sounds can vary in type and frequency between fires, so what causes wood to pop and crackle when burning?

When firewood is burnt a chemical reaction known as combustion occurs in which the solid state of the wood is converted to heat and waste gases.

As the cellulose matter within the firewood turns to heat and gas, some of these gases can become trapped within the pores of the wood.

Combined with steam created from the evaporation of moisture within the firewood, the waste gases from combustion expand due to the heat and must find their way out of the wood.

The process of steam and gases forcing their way out of the firewood creates the noises you hear in the form of pops and crackles.

The main things that influence how much firewood pops and crackles are:

  • The type of wood being burnt.
  • The moisture content level of the firewood.
  • The efficiency of the combustion process.

Type Of Wood

The type of firewood burning in a fire can have an effect of how many pops and crackles you can hear from your fireplace.

Softwoods typically have a higher sap content compared to hardwoods. The higher sap content of softwoods means that more popping and crackling noises can occur.

The sap can expand and cause further blockages within the firewood, providing less of a means for gases and steam to escape. The increased number of pockets of trapped air inside softwood logs can create more popping and crackling noises as these pockets of air finally find their way out.

Therefore, if you’re looking to hear more pops and crackles from your fires look to burn softwood logs.

For fewer pops and crackles from your fireplace look to burn hardwood logs.

Moisture Content Of The Wood

The moisture content level of firewood can also influence how much firewood will crackle and pop in a fire.

Firewood higher in moisture content will typically produce more noises compared to firewood that is lower in moisture.

Moisture within the wood will evaporate and expand due to the temperature of the fire, and the fire can make pops and crackles when the moisture forces its way out of the wood in the form of steam.

Firewood higher in moisture content can produce more popping and crackling noises because there is more moisture contained within the wood. This can lead to more pockets of steam escaping the wood and making pops and crackles.

Unseasoned ‘green’ wood will typically be much higher in moisture content compared to properly seasoned or kiln dried firewood.

Green Wood Moisture Content
Unseasoned firewood that is higher in moisture content can produce more pops and crackles but will also burn highly ineffectively in a fire

However unseasoned wood will burn highly inefficiently and struggle to catch fire, and so it’s never recommended to burn unseasoned green wood.

The Environmental Protection Agency recommends that the moisture content of firewood should be between 15 and 20%. Within this range firewood has a low enough moisture content that it doesn’t struggle to burn, but also isn’t too low that it would burn too quickly to be efficient.

Fully seasoned wood should therefore have a moisture content level of lower than 20%.

Moisture Firewood
Properly seasoned firewood that is below 20% moisture content is best for popping and crackling fires

If you’re looking to get more pops and crackles from your fires then look to burn seasoned firewood with moisture content of just under 20%. Enough moisture will still be retained within the wood for it to produce these noises while also being able to burn effectively on your fires.

Find out more about seasoned firewood in another one of our articles here.

For reduced popping and crackling noises you may also want to look at burning kiln dried firewood. We’ve found kiln dried firewood to be much lower in moisture compared to seasoned firewood, with moisture levels down in the single digits.

Firewood Moisture Content
The moisture content of our kiln dried firewood was so low our moisture meter couldn’t provide a reading. Low moisture firewood will typically produces less pops and crackles

Learn more about kiln dried firewood here.

Efficiency Of The Fire

How efficiently a fire is burning can also have an impact of whether your fires are producing pops and crackles.

Properly seasoned firewood low in moisture content will help a fire to burn efficiently, but the airflow to and from the fire can also have an effect on how well a fire burns.

A fire needs a constant supply of fresh air to keep burning. If there’s a lack of air there can be incomplete combustion of the wood leading to lower temperature fires and more smoke being produced.

You may find that hotter burning fires can produce more popping and crackling noises because the wood can be combusted and gases created at a faster rate, giving more opportunity for these gases to get trapped and force their way out with a pop and crackle.

Sufficient air supply is an important aspect of any fire and so ensure that you either have an air vent or window open in the room if your fires are struggling.

While fresh oxygen is required to keep your fires burning hot, waste gases also need to be removed from the fire at the same rate. It’s therefore also important to have a good draft on your fires if you want to be able to hear those pops and crackles.

For more information we have guide to improving the draft on your fireplace right here.

Does Seasoned Firewood Pop?

Seasoned firewood is the perfect choice of firewood for hearing the most amount of pops and crackles from your fires. Properly seasoned firewood will typically have retained enough moisture for steam to escape and produce popping and crackling sounds.

Firewood can typically only be considered properly seasoned once it has reached below 20% moisture content, in which it will burn its most efficiently in a fire.

At this moisture level firewood is dry enough to catch fire and burn without any issues, but also not too dry that it would burn too quickly to be an efficient source of heat.

This amount of moisture in seasoned firewood helps to keep the logs burning for a reasonable amount of time, but it also enough moisture retained that it can provide a greater opportunity for the firewood to produce pops and crackles.

Seasoned Firewood
Properly seasoned firewood is great for hearing those pops and crackles

How To Stop Firewood From Popping

To reduce the amount of pops and crackles from your fires look to burn kiln dried firewood that is very low in moisture content. The typically reduced amount of moisture within kiln dried wood compared to seasoned firewood can lead to more infrequent popping and crackling noises from fires.

Due to the humidity of the atmosphere kiln dried firewood can be able to reach lower moisture content levels compared to when seasoning firewood outside through air drying.

Firewood can only be seasoned down to a certain moisture level depending on the humidity of the air around it. Lower moisture levels can be reached by kiln drying the wood where the humidity of the atmosphere doesn’t affect how dry the firewood can be.

The higher the moisture level of firewood, the more pop and crackle noises can be produced as the excess water tries to escape.

If you’re wanting to stop your firewood from popping look to use kiln dried firewood with a very low moisture content level.

We’ve found our kiln dried firewood to be much lower in moisture content compared to our seasoned firewood, and we also notice that our kiln dried firewood burns quieter as a result.

Why Does Some Wood Pop More Than Others?

Some types of wood popping and crackling more than others can be as a result of the difference in moisture and sap content. Seasoned softwood logs have the potential to produce more pops compared to kiln dried hardwood logs because of higher moisture and sap levels.

Wood with higher sap content, such as softwood logs, can act much like trapped moisture escaping the wood and making the traditional fireplace sounds.

What Firewood Pops The Most?

If you’re looking to get most pops and crackles from your fires look to burn properly seasoned softwood logs.

Firewood with the right amount of moisture and higher in sap content will be able to produce more of your favorite fireplaces sounds.

Properly seasoned softwood logs such as Pine, Cedar, Spruce and Douglas Fir with a moisture content of just under 20% are therefore the best choice for when you want the most pops and crackles from your fires

Further Reading

A Guide To Seasoned Firewood

A Guide To Kiln Dried Firewood

How To Season Your Own Firewood

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