Sauna Rocks. They might seem like a simple component of your sauna, but they are absolutely crucial to achieving that authentic, deeply satisfying heat. At rockscapes.net, we get countless inquiries about these unassuming stones. Whether you have a wood-burning sauna stove or an electric sauna heater, understanding sauna rocks is key to unlocking the full potential of your sauna experience.
What Kind of Sauna Rocks are Best for Your Sauna Stove?
The debate around the best type of sauna rocks often leads to discussions about igneous rocks, particularly volcanic or lava rocks. While lava rocks boast a high heat capacity, our experience at rockscapes.net has shown that they don’t retain thermal mass as effectively as other options. Why is thermal mass so vital? It’s the secret to that luxurious, dense heat that truly defines a sauna. Think of the difference between the sustained warmth of heavy, water-filled radiators versus the fleeting heat from thin electric baseboards. That deep, penetrating heat comes from thermal mass.
There’s a common theory suggesting that sauna manufacturers sometimes promote volcanic rocks because their lighter weight makes them more economical to ship. However, for true sauna aficionados, performance trumps shipping costs.
Why Granite Rocks are Our Top Choice for Saunas
At rockscapes.net, we are firm believers in the superiority of granite rocks, especially rounded, aged granite stones sourced from locations like the icy shores of Lake Superior. We specifically seek out rocks that are free from cracks and crevices. This is crucial because of the common concern about sauna rocks exploding. Yes, if you use rocks with internal fissures that allow water to seep in, the rapid heating can indeed cause them to fracture explosively – a phenomenon known as hydrofracturing. If you’re interested in the science behind this, you can explore resources on Hydrofraction.
However, the solution is simple: opt for non-porous, dense granite rocks for your sauna stove.
Here’s a simple test we recommend: take two prospective sauna rocks and strike them firmly against each other. If they withstand the impact without cracking or breaking, you’re likely holding two excellent sauna rocks. This rudimentary test is a practical way to ensure the strength and stability of your sauna rocks.
What Size Sauna Rocks are Ideal for Optimal Heat?
When it comes to sauna rock size, we recommend a range from softball to golf ball dimensions. This variation isn’t arbitrary; it’s based on how different sizes interact with heat and steam. Different sized sauna rocks hold and release thermal mass and steam (löyly) uniquely when water is ladled onto them.
In a properly heated wood-burning or electric sauna stove, the rocks accumulate heat. When water is poured over these hot rocks, it transforms into steam, a process that temporarily cools the rocks. Larger, softball-sized sauna rocks possess greater thermal mass, allowing them to retain heat more effectively and recover temperature more quickly. Smaller, golf ball-sized rocks react more rapidly to water, producing steam readily, but they lose thermal mass more quickly in the process.
Therefore, a combination of different sizes is optimal. This mixture provides both rapid steam generation and sustained heat, ensuring a consistent and enjoyable löyly experience.
The Fundamental Role of Sauna Rocks in the Sauna Tradition
To truly understand the significance of sauna rocks, consider the savusauna, the ancient smoke sauna – the earliest form of sauna. Savusaunas are fundamentally “simply a room containing a pile of rocks, but without a chimney.” In this traditional design, rocks are heated directly by a wood fire, often for hours, using a substantial amount of wood. Once the fire is extinguished, the accumulated heat is entirely contained within the rocks, radiating warmth into the sauna.
This core principle – heated rocks as the heat source – is what fundamentally distinguishes a true sauna from, say, an infrared heat room (which we at rockscapes.net often differentiate from traditional saunas). The rocks provide a deep, radiant heat and the capacity to create löyly, the hallmark of the authentic sauna experience.
Think of building your collection of sauna rocks as an ongoing journey, not just a task to complete. Whether you are hiking in nature, strolling along a beach, or even noticing suitable stones in your neighbor’s landscaping (with permission, of course!), keep your “granite sauna rock radar” active. And when you have your rocks ready, you might wonder, how much water should you actually toss on those sauna rocks? Let’s explore that next.
Mastering Löyly: The Art of Pouring Water on Sauna Rocks
Drawing a parallel to the advice of the legendary pool player Minnesota Fats, who famously said there are only two ways to hit a pool shot – “soft and softer” – there’s a similar nuanced approach to pouring water on sauna rocks. Start with a small amount of water, and then add a little more as needed. You can always add more water to create more löyly as your sauna session progresses.
As our friend Clint emphasizes, all sauna stoves are designed to withstand water. Sauna rocks act as a thermal mass, storing heat energy. When water is poured onto the hot rocks, this heat energy is transferred to the water, instantly converting it into steam. This steam, in turn, carries the heat and transfers it to your body upon contact with your skin.
While you could dramatically toss a liter of water onto the rocks all at once, attempting to “ride it out,” this more macho approach is often best reserved for advanced sauna techniques like reverse cycling. For most sauna sessions, moderation and gradual addition are key.
The steam generated from water meeting hot sauna rocks, the löyly, is often described as a deeply spiritual experience. It involves the release of negative ions and a unique combination of elements: Fire (from the sauna stove), Earth (the sauna rocks), and Water (transformed into löyly). This confluence creates an atmosphere akin to the invigorating freshness near waterfalls and rainbows – something truly special that transcends mere words.
Bonus Tip: Gradual Water Application for Longevity
Starting with a smaller amount of water and gradually adding more is not only a more controlled way to create löyly, but it’s also gentler on your sauna stove. This approach minimizes thermal shock, potentially reducing fatigue on your stove over time. Furthermore, by adding water incrementally, the rocks are less depleted of their thermal mass and can respond more quickly and effectively with each subsequent pour, giving you that satisfying sizzle and burst of steam.
Addressing a Common Misconception: Temperature and Steam
It’s a common misconception that tossing water on sauna rocks increases the air temperature in the sauna. In reality, the thermometer might not register a significant rise. However, it feels much hotter because the heat is being transferred much more efficiently to your skin via the water vapor. Steam carries heat far more effectively than dry air, which is why löyly feels so intensely hot.
7 Essential Things to Know About Your Sauna Rocks
To delve deeper into the world of sauna rocks, we consulted Dick from Scandia, Minnesota, a seasoned expert with 33 years of experience in Research and Development at the Andersen Corporation (Windows), specializing in design, project management, and materials research. Dick shared invaluable insights that every sauna enthusiast should consider:
You Can and Should Consider Collecting Your Own Sauna Rocks
If you are drawn to the idea of hand-selecting your sauna rocks, you’re likely someone who appreciates a wood-burning sauna. There’s a certain type of person who meticulously prepares for a sauna – cutting, drying, splitting, and stacking wood with care. This embodies the “Gestalt Principle” in action: the preparation is as integral to the experience as the sauna itself. For such individuals, seeking out and collecting their own “sauna stones” (as Dick prefers to call them once they are in the sauna) further enriches the entire ritual.
You might notice we’ve used both “rocks” and “stones” – Dick clarifies that he thinks of them as “rocks” in their natural environment and they become “stones” once they are chosen and placed within the sauna heater, signifying their purpose and integration into the sauna experience.
A Word of Caution Regarding Rock Collecting Ethics
Gathering stones for your sauna is distinct from casual rock collecting. While picking up a pretty agate from a landscaping bed might seem harmless, removing a whole bucketful of rocks from public beaches, parks, or private land without permission is not acceptable. Be mindful and only collect rocks from land you own or with explicit permission. A responsible and often fruitful alternative is to visit a local landscape supply company or nursery. Many of these businesses will allow you to sort through their piles and hand-pick the “perfect” sauna stones.
The Critical Importance of Stone Properties
The sauna stones are the delivery system for the steam, for the löyly. Their properties – size, density, porosity, and surface texture – all play a vital role in efficiently transferring heat from the stove to you through steam. If the stones are too small, they won’t retain sufficient heat to produce löyly for a satisfying duration. Conversely, if they are too large, they will take excessively long to heat up, delaying the sauna experience.
A stone with a slightly rough, fractured surface is ideal because it provides more surface area for water to interact with, resulting in greater steam production. However, stones that are too irregularly shaped or stacked too tightly can impede the free flow of heat and water through the rock pile. On the other hand, if the stones are stacked too loosely, water will pass through too quickly without fully vaporizing.
Dick prefers stones about the size of his fist, incorporating a few larger and smaller ones to achieve a balanced fill within his stove. It’s crucial to note that owners of modern electric sauna stoves need to be particularly mindful of stone size and placement, as improper loading can shorten the lifespan of the heating elements.
Black Rocks Matter: The Physics of Heat Absorption
It might sound like a slogan, but “Black Rocks Matter” holds true in the context of sauna stones. Darker rocks absorb and radiate heat more efficiently – it’s simply physics. The commercially available “Finnish” sauna stones are typically dark in color for this very reason.
Navigating the Types of Stove Stones: Beyond Marketing Hype
You’ll often encounter marketing claims from companies asserting they sell “the only correct stones,” “the only real sauna rock,” or “the correct type.” These are often marketing tactics designed to convince you that their product is superior. While selecting appropriate sauna rocks is indeed a safety consideration, the truth is that any structurally sound igneous rock will function effectively in a sauna. Unless you possess the highly refined sensibilities of a “100% Finnish” sauna purist, you’ll likely be hard-pressed to discern significant differences between various suitable igneous rock types.
Without delving into a full geology lesson, a simple rule of thumb is: if you can easily scratch material off the rock with just your fingernail, DO NOT USE IT!
Avoid sedimentary rocks (like sandstone, shale, and limestone) and metamorphic rocks (such as slate, marble, and quartzite). These rock types are generally too soft, prone to fracturing, or may contain moisture that can lead to dangerous “popping” or cracking when heated.
The ideal sauna rocks are igneous rocks. Good examples include Vulcanite, gabbro, peridotite, Basalt, Olivine, and Granite. Note that while Obsidian and Pumice are also technically igneous rocks, they are not well-suited for sauna use. Obsidian is too smooth, causing water to run off too quickly without vaporizing efficiently. Pumice, being very light and porous, cools down too rapidly and lacks the necessary thermal mass to provide sustained heat in a sauna.
If you are uncertain about identifying rock types, a quick internet search for “igneous rocks” can provide helpful visual guides. You can also look for geological maps of your region to identify the predominant rock types in your area. For some, finding suitable sauna rocks might become a part of travel and vacation – perhaps bringing home a bucketful at a time, depending on your travel companions’ patience!
Proper Loading of Sauna Rocks: Cleanliness and Arrangement
Before loading your chosen stones into the rock chamber of your sauna stove, it’s essential to wash and rinse them thoroughly. This removes any dirt, debris, or loose particles that could create unpleasant odors when heated or soil your sauna floor.
Depending on your specific heater design, begin by placing the largest stones at the bottom and then gradually use smaller stones as you fill upwards. Stack the stones in and around the rock chamber until it is full, perhaps even slightly heaping. The goal is to achieve a balance: you don’t want the stones packed so tightly that airflow is restricted, but they should be close enough together to ensure that water poured over them doesn’t simply run straight through without vaporizing into steam.
Sauna Rock Replacement: Recognizing When It’s Time
Sauna rocks, like all materials subjected to thermal stress, will degrade over time. While high-quality rocks should last for many years, some inferior types might crack and crumble within a year – these are definitely rocks to avoid. Even good rocks will eventually break down and become smaller due to the repeated heating and cooling cycles. The rocks closest to the heat source typically degrade first due to greater thermal expansion and contraction.
Using room temperature water, rather than very cold water, to create löyly can help reduce thermal stress on the rocks. Similarly, pouring smaller amounts of water at a time is gentler than dousing the rocks with a large volume all at once. It’s better to add a cup of water every few minutes than two cups simultaneously.
When you notice your sauna rocks are increasingly cracked, becoming smaller, and leaving debris on the floor, it’s time for replacement. Simply remove all the old rocks, and then you can combine the still-usable larger pieces with your new rocks when reloading the stove.
The Spiritual Dimension of Sauna Rocks
As eloquently stated, “A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral sauna.” This captures the essence of sauna rocks – they are more than just stones; they are the heart of the sauna, imbued with a deeper meaning and connection to the sauna ritual.
Where to Find Sauna Rocks for Your Perfect Sauna
So, you’re nearing the “Finnish line” of completing your authentic sauna project. You’ve diligently followed every step of the DIY ebook, properly cured your sauna stove, and added the finishing touches. You’ve even invited friends for the inaugural sauna session.
Everything is ready, but wait! “I need sauna rocks!”
While an impromptu trip to the shores of Lake Superior might be appealing, it’s not always feasible. And despite the vastness of beaches, there’s a certain unease about hauling a 5-gallon pickle bucket to a public beach to collect “free-range organic sauna rocks.”
What about railroad tracks? The fringe theory about “asbestos from train brakes in dem der rocks” raises concerns. And then there’s the whimsical thought: if everyone sourced their sauna rocks from train tracks, would we still hear train whistles?
So, what’s a morally and practically conscious sauna enthusiast to do?
The answer is simple: Landscape Center!
Landscape Center!
Landscape Center!
For a modest cost, places like Landscape Love in South Minneapolis and similar landscape supply centers offer an accessible and ethical source for sauna rocks. Bring along a milk crate or a 5-gallon sauna bucket, and you can hand-select from piles of landscape rocks, finding a great assortment of golf ball to softball sized rocks perfect for your sauna.
With the right sauna rocks in place, you’re now ready to experience the profound and invigorating heat of a truly authentic sauna. Explore rockscapes.net for more expert advice and resources to enhance your sauna journey.
