A camping trip just isn’t the same without a roaring fire to sit around at night. Who knows how many stories have been told, and how many s’mores have been made, in front of a dancing blaze surrounded by family and friends. At the same time, who knows how many people have been startled by a sudden pop from the fire, or been bathed in a rain of sparks!
Crackling wood is something we’ve come to expect while it’s burning, but that doesn’t mean it’s comfortable (or even safe, depending on the circumstances). But why does fire pop? And is there anything you can do to prevent it?
- Wood contains water, sap, or materials in “rooms”; heat turns water and sap into steam, causing wood to pop.
- Dry wood reduces crackling; use a moisture meter if unsure.
- Aged wood has less moisture and is preferable for burning.
- Hardwoods like oak and maple pop less than softwoods.
- Splitting wood with an axe exposes dry interiors, minimizing popping.
Why Does Fire Pop?
Asking the question “Why does fire pop?” might seem silly and inconsequential upon first inspection. But we’re curious souls here at Untamed Space, and our aim is to satisfy the curiosity of people like you as well. So, here we are.
However, while it’s easy to view this all as a fun fact, popping firewood does have consequences worth noting. We’ll mention those a little later on, but before we continue any further, let’s start at the very beginning.
How do fires burn?
Fire: How It Works
It’s a fascinating topic if you’ve got the time to dive a little deeper into how fire works, but for now, here’s the basic overview.
Fire needs three things in order to burn: heat, fuel, and oxygen. Take away any one of these things, and the fire will cease to exist. In the case of a campfire, the wood is the fuel, your lighter (or matches, or flint and steel) provides the initial burst of heat, and the oxygen is found in the surrounding air.
So, how does it work? Well, fire is the product of a chemical reaction between an oxidant (in this case, oxygen) and something combustible (the wood). If there’s no oxygen, this chemical reaction can’t take place, and the fire is snuffed out. Naturally, the same happens when all of the fuel has been consumed as well.
What Causes Popping?
If you’ve spent any significant amount of time around campfires, you know that some pop a lot more frequently than others. To understand why that is, first we need to talk about what causes the popping in the first place.
Inside every log are little “rooms” that have trapped water, sap, or other materials. After the wood has been tossed in the fire, the heat makes the water and sap boil until it’s all been transformed into steam. The steam exerts pressure against the room it’s been trapped in, eventually causing it to – you guessed it – pop.
With this in mind, it’s safe to say that wood with more moisture trapped inside will pop and crackle more frequently as the pent-up steam tries to escape. But is this a problem? And what can we do to minimize the amount of popping?
The Dangers of Popping
When I was younger, I used to think it was fun when wood popped. You never really knew when it was coming, and the sudden noise was exhilarating, especially when sparks would go flying with it.
However, it’s those sparks that can cause problems if they get out of hand. Building a campfire inside a pit or ring can minimize the danger, but every time a spark goes flying, you run the risk of starting another fire. A fire that can’t be controlled as easily, at that.
This is especially true if you find yourself in an area suffering from drought, or if it just has a lot of dry grass in general. It doesn’t take much for materials like that to light up, so the more you can minimize popping, the better. Likewise, it’s never good to set your tent up near a crackling fire in case a hot fleck of ash decides to burn a hole through the wall.
Aside from that, though, we know it’s the wet wood that pops more (after all, it’s the moisture inside that creates this phenomenon). Wet or green wood doesn’t burn as efficiently, which means it will be harder for you to light, and harder for it to stay lit. If it’s your only option, there’s not much you can do about it when you need a fire for warmth or cooking. However, when possible, only use local wood that’s older and thoroughly dried out. Not only will it burn better and longer, but you won’t have as many annoying and potentially dangerous pops that send sparks flying.
How to Prevent a Fire from Popping
Potential danger aside, it’s just more comfortable to stay seated around a quiet, tame fire. You’ll be able to draw closer to it without the fear of getting hit by something hot, and it produces an atmosphere more conducive for relaxation. So, now that we know what makes wood pop, here are a few steps you can take to minimize this irritation:
1. Only Use Dry Wood
I mentioned this briefly already, but dry wood is far less likely to crackle and pop than wet or green wood. Sometimes it can be hard to know if wood is sufficiently dry, but there are a few cases where you’ll know immediately. If your wood has been freshly cut, exposed to rain or high humidity, or hasn’t been seasoned long enough, it’s likely too wet to use.
However, you often won’t know the state that the wood is in when you find it. Perhaps it rained a few days before you arrived at your campsite, so despite finding fallen branches that look dry, you unwittingly grab fuel that hasn’t had enough time to air out yet. To give you more confidence in your decision making, you can use a tool called a moisture meter to determine how saturated an item is. It’s not required by any means, but I find it to be a handy tool when I want to know the water content of something before burning it.
2. Look for Old Wood
This one goes hand in hand with searching for dry wood. Freshly cut branches, or trees that have recently fallen over, will still have a lot of water and sap flowing through them. Aged wood, on the other hand, will have had more time to dry out, making it a prime candidate for firewood.
This is one reason why you don’t want to snap off branches from a live tree to use as kindling. Well, that and the fact that you’re damaging the tree in the process. Finding chunks of dead wood on the forest floor is the best option for all parties involved.
3. Use Hardwood
Hardwoods like oak and maple are also going to pop less than softwoods like pine. With a much lower moisture content than softwood, hardwoods barely produce any steam at all, which is what causes the popping in the first place.
And not only that, hardwoods also contain less sap and resin than other varieties of wood. This is important because, as the sap or resin heat up, they expand and seal up any nearby cracks or crevices. Moisture that might have escaped without a problem will now be trapped inside this freshly formed seal, causing the wood to pop even more frequently than it would have otherwise.
4. Make Your Fire on a Dry Surface
Wood is porous and easily absorbs any moisture it comes in contact with. So even if it’s dry when you find or purchase it, placing it on a wet surface will defeat the purpose.
However, sometimes your options are limited, and it just isn’t possible to make your fire in a place that’s completely dry. You’ll have to compromise a little, but the best way around this predicament is to change the way that you arrange the logs inside the fire pit. A teepee shape, for example, is one of the best options for keeping wood as dry as possible, even when placed on damp ground.
5. Only Have Wet Wood? Here’s How to Dry It
If you only have access to wet wood, it may be time to get a little creative. First, you’ll want to take all of your damp fuel and gather it together. Grab some tinder and kindling and use it to form the shape of a teepee before lighting it. This is what you’re going to use to dry out the larger logs that will be your primary source of fuel later.
Speaking of larger logs, stand them up on their ends in a circle around your teepee of tinder and kindling. You want them close enough to the fire created by your teepee where they’ll start to steam and dry out, without actually catching on fire just yet. Once you’re satisfied with how dry they are, toss them into the fire and enjoy!
6. Use an Axe
While it might be more of a bushcraft technique that’s especially useful in the winter months, using an axe is a great way to produce dry wood. Unless it’s been thoroughly saturated, it’s mostly just the outside of a branch that absorbs water, leaving the inside dry enough to light.
Take an axe (or another sharp-edged tool) and use it to split the branch in half, exposing the dry interior. You can either light it up like that, or continue to shave off the damp portions on the exterior, but that’s all you need to do to get access to dry firewood. It may still pop a little, but in extreme situations, beggars can’t be choosers.
When lit on fire, wood is bound to crackle and pop from time to time. However, the more you can minimize this effect, the more comfortable you’ll be basking in the warmth of the flame. Not only will it be less startling, you also won’t have to worry about sparks flying toward you or your gear, potentially causing unwanted damage.
Ultimately, to reduce popping, just do your best to find dry, aged hardwood. Whether it’s oak, cherry, hickory, or something else, this is going to be your best option for creating a soft, gentle flame that produces an atmosphere of relaxation.