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.
COVID sure has made life strange and difficult for all of us. Patterns of living have been upended and new norms have emerged that will probably stay with us. One pattern that became very clear was that many people have decided to make their homes more livable, especially when it comes to outdoor spaces. Fortunately for me, this includes home saunas, which have seen a huge spike in demand which I am tying to keep up with. But, there has also been a huge increase in demand for materials associated with these types of projects causing me delays and headaches. Like the toilet paper that disappeared early in the pandemic, framing lumber, cedar, and pressure treated decking have all but vanished in some stores. Not only are people buying more for their home improvement projects but the triple whammy of last years wild fires, Covid taking out some of the workforce, and tariffs on Canadian lumber has caused major shortfalls and huge price increases in building supplies. Yesterday I bought a single sheet of OSB (oriented strand board— the most ubiquitous of building materials and the sheathing on virtually very house) and it cost me over $27—$20 more than what I paid 18 months ago. Everything else from 2×4’s to steel plate has doubled.
The contracting business depends a lot on giving a solid price well ahead of time so that the buyer can plan and budget. I’m working on projects I bid 6 months ago at prices I thought I could expect to pay when I got to the checkout. How can I give quotes when the prices are going up like that? Often, I have to eat those unexpected cost increases. Maybe the prices will fall, but I think, like wearing masks in grocery stores, we have hit a new norm.
I can’t absorb all this pricing mayhem so I’ll have to pass some of it on to you- my valued customer. If you are doing a DIY project and using a book written ten or more years ago, be sure to check prices; the big box stores do a pretty good job of posting it all online. And when you ask me how much something cost remember that cost, like time is a fleeting thing.
The most important thing to remember though is: how much is a sauna worth to you? It is measured not in dollars but in real value added to the quality of your life. In other words: priceless.
With over 30 years experience working in the building trade, Rob readily dispenses his knowledge to clients, a clear, professional communication style. If you need in-depth information on how to build your own sauna or need drawings/plans whether you are a builder, DIY builder or architectural firm I offer plans and consults. BOOK A CONSULT HERE >
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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A lot of building science is pretty theoretical because, no matter how much research you do, at the end of the job most of the work is hidden in the walls. Unless you come back to do renovations, or worse, get a dreaded “call back” for something gone seriously wrong, you rarely get the opportunity to see how your work performs. I am not talking about cosmetic details like nail holes that don’t get filled or rough edges that didn’t get sanded, but about how well materials hold up to the heat or how well you have managed moisture movement through the walls, either as precipitation working its way in, or the more mysterious way that water vapor works its way out. (or inwards in some climates). This moisture is driven by vapor pressure, which can drive water molecules through most any material given the right humidity and heat differentials— something a sauna has a lot of. I learned about vapor pressure when I realized that my hollow steel yard sculptures were inexplicably filling up with water. My welds are very solid and water-tight but somehow moisture was penetrating the steel, condensing and not getting out. Cutting holes in the bottoms to let trapped water out solved that problem. There’s a bit of molecular science involved here, but suffice it say that vapor pressure is very strong- strong enough that when I throw water on the hot rocks my sauna door pops open as if the löyly has scared a ghost out of hiding. (Read previous post about Insulating Saunas)
Thinking about all of this has left me wondering what is happening in my sauna walls; am I doing a good job? is the insulation holding up? is water getting trapped?
Yesterday I had to do some retrofitting on the first mobile sauna I built in 2013. I exchanged the Scandia gas heater for a wood burner and got to peer into the dark interior of the walls. This is a sauna that has seen heavy and very hot (200°+) usage. The walls were built with cedar inside and out with only a 1″ layer of foil faced polyioscyanurate foam board in between the studs.
Here is what I found:
There was no damage from trapped moisture and the foam board looked as good as new; the foil facing still shiny! There was some high-temp fiber fax insulation used around the gas heater; a rodent had gotten into this (despite my filling gaps around the gas line with steel wool) and made a stinky little nest.
So this confirmed my use of the polyisocyanurate board, which has a service temperature of 250°F and my disdain of fiberglass type materials (because rodents love it).
polyisocyanurate board, original state
fiberfax mouse nest
Melted EXP (expanded polysytrene) foam
On my desk I have a piece of EXP (expanded polysytrene) foam I pulled out of a failed sauna I was asked to repair. It looks like one of my steel sculptures from my Landform series – a flowing, green landscape (of melted plastic). Its service temp is listed as 150° F. All materials have material data sheets, usually available on the manufacturers web pages. I consult these whenever I am unsure about materials, especially given that the extremes of the sauna are like the extremes NASA engineers have to deal with. Clearly there is a correlation between science and reality, even if it is happening unseen inside the walls of your sauna. So when choosing materials, listen to the science, learn from observation and don’t just buy the cheapest materials or use only the easiest approach. Consult with the experts. Sometimes there is more to it than meets the eye.
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The New England coast is beautiful and varied, from the dramatic rocky shores of Maine, to the sandy beaches of Cape Cod to the rocky moraine of Long Island’s north shore. The one thing New England’s coastal waters are not is warm. I remember swimming in Maine when I was in art school in Portland: I would get all hot and sweaty by running or biking to the beach, and jump in and swim a brisk few hundred yards to the astonishment of onlookers who dared not go in past their knees. For most people the swimming season in Maine consist of two weeks in August.
It is no wonder that my last several mobile saunas have found homes near the coast—what a perfect way to extend the swimming season! Cold water and saunas traditionally go together. Ideally the sauna is situated so one can plunge into a lake, pond, stream, or the ocean after each round. With a sauna on wheels you can pull up to your favorite dipping spot and indulge yourself anytime of year. There is nothing like the thrill of jumping through a hole in the ice or plunging next to waterfall in the whiteness of winter.
The mobile unit is fairly clandestine – once the stove reaches temperature the chimney smoke is invisible; no one will suspect you are nearly naked inside basking until you burst out and head for the water. I haven’t had the pleasure of sauna-ing next to the ocean but one of these days I’ll have to travel back to Higgin’s Beach in Maine, sauna in tow, and give onlookers as thrill as I defy the icy winter water with a post-sauna dip.
You ask how or why electric mobile? There are a number of reasons why going mobile makes sense, especially if you rent. You need no permits or special permissions. You just park it in your yard and use it. You can take it with you on vacations or just for a Saturday down by the lake, you can even enter it in a parade. But why electric? Electric is no longer the inefficient dark horse of the energy world that it once was. It can be generated cleanly by wind or solar and is cheaper, cleaner, and easier to use than gas or oil. Although any purist will tell you a wood-burning sauna is the real deal, in some places wood is not so easy-—firewood may be hard to come by and to difficult store, and your neighbors may too close for comfort or offended by the occasional whiff of smoke. Since I’ve eliminated gas burners from my repertoire (for reasons I won’t go into here) an electric mobile sauna is the next best thing. All you need is a place to plug it in.
When clients ask me to create a sauna they often push me to do things I might have never considered doing. I’ve been requested to make saunas in spaces I thought were too tiny, on trailers, deep in the woods next to a pond, or to convert a cheap shed or laundry room. The most recent project to leave the shop is an electric mobile sauna. The owner has a Tesla electric car so an electric sauna just seemed to make sense. She also wanted the benches to flip up so it could be a mobile hot-yoga studio. The colors were more of an emotional choice: I painted it Sea Reflections blue like the ocean, where she likes to swim all year, with a Bonfire Red door to beckon her into the warmth of its interior, and Vanilla Ice Cream trim because, well, who doesn’t like ice cream, especially after a sauna?
The how, is simple: an 8 KW heater with a standard RV type hook up and a fifty-foot very-heavy extension cord that connects to standard car charging port (or special outdoor outlet). This will also work in many campgrounds with RV hook-ups. In a pinch, it can also be run off an 8500-watt generator.
This sauna also has a solar powered low-voltage lighting system, just so there can always be light and because low voltage systems are safer and more versatile than 120 volt lighting. I’ve been using these in some mobile wood burners and freestanding units. The neat little solar panel is a conversation starter; people are suddenly aware that the unit is more than a fancy tool shed trailer. When I tell them it’s an electric sauna, the little 25 watt solar panel gets a second glance.
What I envision next (but probably won’t consider doing unless a client pushes me) is a fully solar electric sauna. It would have to use Tesla’s 270-pound Powerwall home battery, which has an 8kw output capacity. I imagine the entire sauna roof would a have to be a solar panel but I haven’t done the engineering on this. This would not be cheap, but if there is someone out there who wants to be the first…. give me a call…
