You’ve probably heard that I’ve spent a lot of time in the sauna but another hot spot I’ve spent a lot of time around is kilns. Specifically foundry kilns and ceramic kilns. Unsurprisingly there is a strong relationship between the two as they both involve getting things hot. In the lost wax casting process, investment or ceramic shell molds are heated to roughly 1500° F, which burns off the wax original- thus the “lost wax” of lost wax casting. This can take hours or even days depending on the mold type and size. A ceramic kiln can get much hotter- up to 3000° F. That is hot enough to melt steel and many other metals.
I learned how to do bronze casting in Art School. It is an ancient process and we did it pretty much the same way that it was done thousands of year ago. We learned to figure how hot things were by using our senses. All objects emit radiation when heated but at about 1100-1300° it become visible. Peering into a hot kiln (safety glasses strongly suggested) is like looking at another world, perhaps on some alien gaseous planet. Solid objects look like they are transparent. Heat and light become the same thing, the heated molds don’t reflect light but emit light. The blast of heat through the spy-hole is like a ray gun. We rarely used pyrometers (hi temp thermometers) and when we did it was only to affirm what our senses were telling us. We would record the smells of things burning off. When the smells were gone, the molds were clean and ready to accept the molten bronze.
When loading the kiln there is always discussion about the hot spots- certain delicate molds need to avoid the heat while larger molds might need it more. There is always conjecture about how the heat circulates; a whole aspect of kiln building is dedicated to controlling the flow of heat within the kiln. Some of this conjecture is borne out in the results of a firing—whether things fire correctly or not. Ceramicist use cones: small tapering forms that bend at specific temperatures. After a firing these will give a true telling of how the firing went. But, despite the science, there is still a lot of mystery and art to the process, so much so that a firing of a large kiln can take on a ritualistic feeling. Staying up late to tend the kiln, as is done with wood fired and other non-automated kilns, drinking beer and heating up pizza on the kiln, tends to add to the aura.
Thinking of all of this makes me think of sauna. Both have been done pretty the same way for millennia with an aura of ritual and involving community. Both have a focus on fire and heat, and, as well studied and commonly practiced as they both are, there is still a bit of mystery involved in each.
A kiln is like a sauna on steroids. The heat is so amplified that its flow and effects are unmistakable. Observing one is a lesson in thermodynamics. In the sauna building culture there is a lot of banter about how to best heat, insulate, and vent a sauna, yet all of it is conjecture based on theory until one sits in a sauna and feels the heat radiating off of the rocks and the wave of löyly hitting you on the sensitive tops of your ears.
When I design a sauna I draw from my years of kiln experience; I think of the heat as visceral substance, almost visible, as in a kiln. I relish the use of my senses to discern quality rather than depending on technology. Even if the sauna is electric with a digital control panel I rely on feel, not the number on the display. I imagine the flow of heat like the way it flows in a kiln. My foundry experience has informed my understanding of sauna in ways that are hard to describe but suffice it say that I have always been drawn to fire and to the mysteries that it holds.
Candle windows hark back to my time at Podunk where the light in the sauna came from a bare bulb in a porcelain fixture outside a little square window into the dressing room. The sauna i s too hot for a standard light fixture, so this arrangement made sense. Later, after I started building saunas, I learned that this was a more modern incarnation of the original candle window, which was literally a window into the dressing room with a shelf for a candle to sit on. These are common in Finland in freestanding saunas away from the house. The window allows for a special kind of spiritual, summoning light into the sauna. Especially on those dark winter nights.
In the sauna tradition, we slow down. The flickering candle light seen from the bench in the sauna, lures you to relax and reflect. Life and relativity. Could there be a more tranquil way to release the stresses of the day?
Although it is this quality of the light that is so important, the candle is totally pragmatic in a very Finnish way. A candle in the sauna room would melt even if not lit, so this was an obvious solution to the problem of lighting the dark interior of the hot room. Despite its pragmatic origins, I find it is also a chance for a little expressive design: it can be round or square, arched or colored. It can have an organic flare to it. Now, with cheap, battery-operated, multi colored LED lights and even fake candles that look real, the light can be more than a simple bulb on a pull-chain porcelain fixture, and be safe. Even if the sauna has built-in electric lighting, the candle window can be a signature element, one that distinguishes a personalized custom sauna from a generic kit.
It’s in the details.
Finnish pragmatic design inspiration comes from making use of what is available at hand and letting that material influence your design. There are many places to incorporate little details and personal touches: stick hardware towel pegs, stone faced stove wall with stones from your backyard, thresholds of locally cut locust, round windows, etc. Think of decorative elements you can hang above the mantle. In my sauna building plans you can purchase and download, there is more about windows, framing information as well as tips on using windows safely in mobile saunas.
wood burning sauna with candle window to dressing room
Here is a collection of the candle window design and builds over the years in and around the Finger Lakes and New York State.
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The Kiuas, or heater, is the heart of the sauna. In a wood-burner, it is commonly referred to as the sauna stove, but a wood stove it is not! There is a lot of misconception around the kiuas and how it is different from a wood stove that you might use in your house.
First, some history. The modern house stove is really a heating device designed to add comfort to your home while conforming to certain safety and smoke emission rules. Typically they are not used as primary heating appliances, unless you live in a cabin off-grid somewhere. Back in 70’s, during the energy crisis, woodstoves become popular as a way to save money. They were pretty much unregulated and varied in design from a kit that consisted of a door and a flue collar you could slap onto a used fifty-gallon drum, to a more complex Vermont Castings wood stove. Earlier stoves had little control over combustion; these evolved into airtight units that could keep a smoldering fire all night, if not for an entire season. I had one of these and didn’t let the fire go out all winter except to clean it. Cleaning the chimneys on these was imperative: when wood—especially if it is not cured for two years— is burned slowly by reducing the combustion air to near nil, creosote forms as the result of the resinous gasses condensing on inside of the cool chimney walls. As a result of the slow burning, these stoves emitted a lot of smoke. After many houses were lost to chimney fires, safety regulations were put into place and stoves were required to use catalytic converters, much like on your car, that reduced emissions. These required a religious adherence to the use of dry wood, lest your catalytic converter clogged up, which most of them did. Those evolved into today’s stoves that use a carefully designed system of baffles and airflow to make stoves burn efficiently. Now, all wood burning home heating device installed in the US must comply with UL (Underwriters Laboratory) safety standards and increasingly stringent EPA standards for particulate emissions. The stoves work well and are very cozy but, by design, they don’t get very hot fast, nor are they meant to burn all night long, not to mention all season long. Because they are intricate with interconnected parts, they are all cast iron. The exception is some stoves made in the pre- catalytic converter era, which were welded steel.
So, that is a wood stove. You may find a used one and think you can build a sauna around it, but the truth is, with the rare exception of one of those 70’s all welded steel (but not a barrel!) stoves, you can’t. You can build a small hot room with a wood stove, but it will never be a real sauna; here is why: A sauna stove, or kiuas, is designed to do one thing: heat sauna rocks. It is the hot rocks that heat the sauna, that produce the burst of löyly steam and that are true heart of the sauna. Early saunas did not have a metal stove- they did not even have the technology to make a metal stove- all they had was wood, earth and rocks. The kiuas was essentially a hollowed out a pile of rocks. The fire was lit within, the room filled with smoke, and, after the rocks got hot, the fire was extinguished and the room cleared of smoke and then the rocks heated the room. The closer you can get to that smoke or Savusauna experience, the better.
A sauna stove is not a wood stove; it fires hot and fast, it burns sticks, not logs. It’s job is to heat rocks. If fired correctly, you will never have to clean the chimney- a hot fire will combust all of the sticky wood gas. It is welded steel—which can have water poured over it while red-hot. Cast iron cracks or explodes when subjected to this. It can take the weight of a hundred or more pounds of rocks sitting on top of it when cherry red. Ferrous metal takes on specific color when heated; at 1400° F. it is cherry red. At that temperature, an 1/8 inch plate of steel is as malleable as taffy on a hot summer day at the beach. I repaired many sauna stoves where the top looked like an egg carton from the stones pressing down on the hot metal, so I started making stoves with half-inch thick plate at the top. I fire my stove so hot that I see dark cherry red glowing underneath the stones. If you fired your home heating wood stove like that, you would be crazy. I swear that sometimes I could read a book by the glow coming off of my sauna stove. I like to push the limits so that I know it is safe.
When you light a sauna stove, you want to fire it, that is, to bring it up to temperature quickly. Use paper and dry kindling and then stuff it full of sticks, not logs (wood scraps from building saunas work great). Because they are for intermittent use, they are exempt from the EPA particulate rules but, the truth is, once it gets going—after about ten minutes—it should burn so hot that there is no smoke at all. Other than the shimmering light from the heat, I can’t tell my sauna is heating up by looking at the chimney. House woodstoves are tame devices, meant to be safe. Sauna heaters are another beast; that is why I will never install a wood burning kiuas in a sauna in or attached to a house. They do burn down now and then.
If you are building your own wood-burning sauna, you may have a building inspector involved or have to get a wood burning appliance inspection for your home insurance and that may require a UL listing. The only heater with UL label on it is the Lamppa Kuuma stove; most of the others are made for the European or Canadian market, which uses different standards, so before you click on “buy” you should have a conversation with any inspectors involved. They may love the idea of a sauna or they may think you are crazy to sit in a small hot room and throw water on a red- hot wood stove, in which case you’ll have to convince them that it’s something that’s been done millions of times without incident. In any case you will need to make a safe installation of your Kiuas – there are clearances and heat shields and floor hearths; none of these can be cheated on, unless you don’t mind owning one of the ones that burns down. There is also combustion air to consider- which is why I like to fire mine from the outside. The sauna stove sucks up fuel and oxygen, better to not be sucking the air out of the tiny room you and your friends will be in. Not such a problem with a house wood stove (but with newer air tight construction and tiny homes, it is).
So, before you get that old woodstove you find on Craigslist, do your research and think about investing in a real sauna stove because the kiuas is the heart of the sauna and the kiuas is not a wood stove!
My stove pipe will get cherry red!
After ten minutes, a hot fire fire should burn clean and smoke-less
All stoves will smoke initially
Nothing bigger than arm your arm!
This armload of ash (the wood) will fire the sauna
Fill it and let it burn hot before closing the ash drawer
All summer long I have eagerly anticipated this week; we have a cottage rental on the lake. It’s the highlight of my summer and a much-needed break from all of the projects I have going on. This year, in addition to the usual activities—swimming, canoeing, beach fires, collecting beach glass and just staring the waves while sipping wine—I’ve added one more: sauna! I’ve brought my wood-fired trailer sauna with me and parked it ten feet from the water’s edge. Nothing beats coming out from the hot steam of a good löyly and jumping into the cool, refreshing lake. It is perfection.
Mobile Sauna by Rob Licht Custom Saunas on Cayuga Lake
Just beyond the reaches of the village of Trumansburg, where I grew up, the settlement of Podunk was home to some 30 people and a cross-country ski shop. The place was run by Osmo Heila, a Finn, who also sold juicers and sauna stoves, and was an ambassador for all things Finnish. There was a rustic ski lodge, a modest circuit of trails, and a sauna. I was good friends with the family and spent winters there skiing the trails and summers taking saunas and hanging out by the creek.
The original owner of the property was also Finnish, and, following tradition, he built the sauna before the house. It was constructed out of locally cut wood and with a modest profile. Despite a few upgrades over the years, it maintained a typical Finnish pragmatic aesthetic. New parts were eschewed in favor of jury-rigged repairs, like the paint can that became part of the stove-pipe. There were a few feminine touches, like curtains in the dressing room, but the sauna room contained only the bare essentials: stove (or kiuas) with its pile of rocks, a water tank heated by the stove, simple benches, and buckets, brushes and loofas for washing. A window, propped open with a stick, provided ventilation. The spalled concrete floor had a drain and wooden slats, called duck boards, to walk on. The pine wall boards had resinous knots that oozed sap into shapes that made us think of strange creatures. Returning to Podunk in the years after high school, it always seemed the same. The same mementos were in the dressing room, the same plastic buckets were on the benches and the creatures on the wall had barely moved. But, like the creek, meandering behind the sauna, it was slowly changing: being swallowed by the bushes, sinking into the earth and eroding away.
Taking a sauna consisted of several sessions of heating up, each followed by a cooling down or a plunge into the creek, and, lastly, a scrub and a rinse in the sauna room. Afterwards, we relaxed in the house and shared food and drink. Eventually, somebody looked at a clock and we all suddenly became aware of the hours that had passed. We called this lost sense of time “sauna time”.
Applied to everyday life, “sauna time” means slowing down, stepping away from technology, and observing the subtle changes. It is an appreciation of all that is impermanent. The continuity of life doesn’t come from holding onto things, but from the rituals, traditions and relationships that one carries in their heart. As the sauna at Podunk slowly degrades into a pile of boards, I am reminded that Sauna is much more than just a building and that building saunas is about much more than just carpentry.
