Stone Boiling Water – How to Disinfect Water with Hot Rocks

by | Sep 22, 2020 | Purifying Water

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Bringing water to a boil is one of the easiest, and most effective ways to purify water. It’s the reason most campaign and bushcraft enthusiasts always carry a metal container that can both hold water, and withstand the heat of flames. But what happens if you ever find yourself stuck in nature without any of your favorite bushcraft gear? That’s where stone boiling comes into play.

What is Stone Boiling?

Stone boiling is the process of purifying and disinfecting water by placing burning hot stones in the water until it’s brought to a boil. At which point, the water can be used to cook and prepare raw foods, or boiled long enough to make it safe for consumption.

At its core, boiling water with hot rocks is a primitive technique that is widely used by survivalists and bushcraft purists in the wild. 

In practice, stone boiling has a rich history, particularly in the Northern American region. Based on archeological findings, indigeounous peoples in Canada and the United States first began using stone boiling to cook food nearly 5,000 years ago.

Importance of Disinfecting Water

When planning a trip off the grid, it’s always important to bring an adequate amount of fresh, clean drinking water. Even if you’re going to be spending the majority of your time lakeside or hiking along a river trail.

The reason being, there’s a good chance that the water you find in the wild is contaminated.

Yes, the crystal clear creak that you set up camp next to can still carry a wide variety of contaminants that could spell trouble for your health. Aside from the debris that you can see, think about the bacteria, viruses, parasites, and other contaminants that made a home in that very same water.

Even if you filter the water before drinking it, you can still be putting yourself at risk. The best way to ensure that your water is safe for consumption is by purifying, and disinfecting it. 

The most common method is boiling water, so that all contaminants are killed. When the water cools, it will be safe for you to drink.

Perfect for Bushcrafting

Bushcraft is a popular hobby shared by people who love spending time in nature. Though it shares some similarities with camping, it’s less about leisure, and more about surviving off the land. Just like our ancestors used to do.

If you’re a bushcraft purist, you’ll try to minimize the items that you bring with you. The problem is, the average person is going to struggle with purifying water in the wild without bringing the essentials, like a small pot or kettle.

Stone boiling is perfect for avid bushcrafters because it relies on all natural materials. At the end of the day, that’s what bushcraft is all about.

Materials You Need

Stone boiling doesn’t require much, but there are some basic materials that you’ll definitely need. Before getting started, we highly recommend that you gather all of the necessary (and optional) materials, and have them ready.

This way, you won’t be left with burning rocks and a container of water without any method of transferring the stones from the fire into the water. 

Container for Water

Finding a suitable container for stone boiling water can get a bit tricky. It needs to be able to both hold water, and withstand the heat and weight of the rocks. For those reasons, we’re going to recommend you go with something sturdy, like wood.

If you’re near bamboo, you should definitely utilize its incredible structure and strength for your water container. If you’re not, you can find a larger piece of wood that has some depth to it. 

Once you have your wood, you’ll want to carve out enough space so that it can hold a decent amount of water. Remember, you’ll be placing a handful of stones in there as well. So, if your container is too small, you won’t be left with much drinking water.

Once you’ve carved out enough space, clean out all the extra debris. The last thing you need is to get a mouthful of splinters when you’re trying to quench your thirst.

When satisfied with the container, the last step is to take it to your water source. Fill it up, and make sure that it actually holds water. If it does, you’re all set. 

Wood and Tinder for Fire

Creating a fire is essential to the stone boiling process. In fact, it’s the only way to get your rocks hot enough so that they will be able to purify the water for drinking.

What you build your fire with will largely depend on the materials around you. But for the most part, you’ll likely be gathering tinder, which is combustible materials like dry leaves or tree bark. That’s going to be how you get your fire started.

Next, you’ll want to gather larger branches and pieces of wood. This will provide enough fuel for your fire so that it can generate enough heat for the stone boiling process. Larger pieces of wood will also help make sure that your fire stays burning during this whole process.

Dry Stones

On the surface, collecting rocks to boil your water seems like the easiest of tasks. However, there are some things you need to know. Partifuclary, which rocks you should and shouldn’t use.

You don’t need to be a petrologist or geologist when collecting rocks. You just need to know a few basic things to avoid rocks completely exploding in your face.

Let’s take a quick look at the following terms, porosity and permeability. 

In this case, porosity refers to the amount and size of the holes in a rock. Ideally, you’ll want to avoid porous rocks, as they are more prone to exploding. This is especially true if they have water in them.

Permeability refers to the ability for water to travel from one pore to another. If a rock is permeable, then it means it’s easier for water to travel between pores, which also makes it more prone to exploding.

Your safest bet is to find smooth, solid dry rocks that aren’t near or in water. This will reduce the risk of explosion when they are placed into the fire to heat up.

Sturdy Branches

Seeing as you’ve already collected tinder and wood for your fire and container, you may be wondering why we’re including sturdy branches as well. The answer is, you’re going to need a method of transferring the piping hot rocks from the fire, into your water. 

You didn’t think you were going to use your hands did you?

The best scenario is to find tong like branches that are connected. If you do, you can easily use them to grab the stones out of the fire. The most probable scenario is that you will find two sturdy branches that can be used to grab, and lift the stones.

These branches should have a decent size. They need to be able to withstand the heat, and also allow you to stand far enough back so that you don’t burn your hands.

Filter or Cloth (Optional)

Even if you collect clear water, it’s going to be difficult to avoid debris, dirt, and charcoal from the stones. The water will still be safe to drink once it’s been boiled, but there aren’t many people who enjoy drinking muddy water.

That’s where a cloth or filter can come in handy. 

If you have a cloth or shirt, you can use it to filter out the larger contaminants from your water. If you don’t have a cloth, you can create your own filter as well. Again, this is strictly for comfort. The water will still be safe to drink.

How to Boil Water with Rocks

Now that you have all the materials ready, it’s time to get to the good stuff. Below, we’ve outlined step-by-step instructions on how to properly boil water with hot rocks in case you ever get caught in a bind and need to hydrate.

Also, keep in mind that you may not get it right on the first try. It’s a tedious process, but once you get the hang of it, you’ll have a new skill that you can utilize at any time.

Step 1: Collect Water

As basic as this sounds, collect your water before you do anything else. It’s never a good idea to start a fire, and leave it on its own while you go venture off elsewhere for a couple reasons.

First, it’s just simply not safe. When a fire is burning, even a small ember can set off a brushfire given the right conditions. The last thing you want is to come back to a raging fire, with all your stuff completely burnt to a crisp.

Secondly, it’s possible that your fire goes out while you’re gone. If you collect your water first, you can then set it aside as you begin the stone boiling process.

Step 2: Build a Fire

Gather your tinder and branches, and begin setting up the foundation of your fire. There are a number of designs that you can use when building your fire, which you can learn more about

However, when it comes to building a fire to heat stones, you’ll want to take a slightly different approach. Make sure that when you’re setting up your fire, you take into account the need to easily insert and remove stones to boil your water.

Once the fire is going, try to avoid moving the wood or branches around too much. Try to leave enough space from the start to make things easier on yourself.

Step 3: Heat Rocks

Once you have a good sized fire going, place the egg sized stones you collected into the burning flame. Allow it to settle into the burning coals so that it can start to retain the heat itself. 

The length of time it takes to adequately heat up the rocks will largely depend on the type of rock you collected, and the strength of the fire. It’s going to be difficult to reach the necessary temperatures if you have a small fire going, so do your best to continue feeding the fire until you feel confident in the heat it can produce.

For the average fire, it should take your rocks anywhere from 30 to 45 minutes to completely heat up. Once they are hot enough, it’s time to remove them from the fire.

Using your branches, carefully remove your rocks one at a time from the fire. They will likely have some charcoal, dirt, or ash on them, but that’s ok. If you prefer, you can quickly rinse the hot stones in water, or tap them on a clean stone to get some of the larger contaminants off.

Step 4: Boil Water

Place each stone in the water one at a time. When dropping the first stone in, depending on how much water you are attempting to boil, you likely won’t see much of a reaction. That’s completely normal.

Continue to place hot stones into your water one at a time until you see the water begin to boil. You’ll know when it’s boiling once you see it begin to bubble rapidly.

Once it reaches its boiling point, you need to let it boil for about 1 minute to 3 minutes depending on your altitude. If you are below 6,500 feet, bring to a rolling boil for 1 minute. If you are above 6,500 feet, bring to a rolling boil for 3 minutes.

Step 5: Cool and Filter

Now for the final step. Now that your water has been boiled and purified, you can safely remove the stones and set them aside. 

You’ll notice your water may be a bit murky or muddy from the stone boiling process, but that’s ok. You can try to avoid drinking any large debris or particles, but the water itself is safe to drink.

If you’re not happy with the quality of the water, you can pour it through a filter or cloth to remove any visible contaminants. Once you’re satisfied, allow the water some time to cool before you try to drink it. This helps avoid any burn injuries.

There you have it. You’ve successfully gone through the complete stone boiling process, which will come in handy in any environment or condition.

Brian Segal

As an outdoor enthusiast, I was drawn to bushcraft at a young age. I constantly find myself trying to learn and improve on my survival skills, and enjoy writing about everything I discover to help pass along to others.

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