Sunday, April 27, 2014

The end — and a new beginning

Thus endeth the lessons on stones. I learned a lot and hope you did too.

And now to consider some other topics.


Thursday, April 24, 2014

Between a rock and a hard place

April the (unofficial) Month of Sauna Stones

My sauna stones mostly quarried peridotite rocks are wearing out. When I swept out recently, many tiny rock crumbles were under the kiuas (the sauna heater), and I noted a few pinholes had been burned into the duckboards by hot falling chunks.

Occasionally, upon sprinkling a dipperful of water, I hear a pop. Oops, another rock just cracked.

Research indicates that each reheating weathers the rocks as the  natural elements do, that they eventually lose their heat-holding qualities. Rocks may need replacing in as little as two years, depending on how often people heat up their sauna. I suppose I’ll be needing new ones soon.

What’s your suggestion — quarried or round? Purchased or found?


Sunday, April 20, 2014

Rock, Rock — who’s there?

April the (unofficial) Month of Sauna Stones   

A large box of rocks came with my sauna — about 70 pounds of peridotite, a dark-colored, angular rough rock. Quarried rocks have lots of rough edges, all the more surface area to make löyly, the steam. They look different than the sauna stones I grew up with, but I like the way the water dances on them.

Over time, I’ve added a pink granite sphere that was found on the Minnesota shores of Lake Superior that reminds me of my grandpa’s sauna stones (the ones we moved).

Two stones were gifts. One is etched with the word “Kuuma” (meaning “hot” in Finnish). The other reads “Sisu” (meaning “determination, bravery and resilience — and more). They warm both my heart and my sauna.

So I’m not a purist about sauna rocks. They do different jobs in my stove. What about the stones you use — are they traditional or new, similar or eclectic, decorative or functional? 

Thursday, April 17, 2014

Crumbles happen

April the (unofficial) Month of Sauna Stones

Now you knowrocks crumble. When they crumble in your sauna stove (the kiuas), the grit clogs up the air spaces between the rocks piled inside. With poorer air circulation, the stove heats less efficiently.

Bernhard Hillila wrote about sauna rocks in his book The Sauna Is. He said, “If they can’t stand the
heat, they ought to stay out of the kiuas.”

When you sweep up the crumbles, take time to check your stones. Are they holding up?


Sunday, April 13, 2014

Sauna stones 102: ceramic rocks

April the (unofficial) Month of Sauna Stones

Ceramic rocks are today’s subject. They add technology to natural materials to create shaped stones with a porous enough structure that allows moisture to collect on their surfaces. Amazing!

Ceramic rocks, unknown to our grandparents, were developed for use in electric sauna stoves, perhaps specifically for far-infrared saunas. They are manufactured to be less prone to cracking, and thus more durable. While that’s an important quality for a much-used public sauna, where replacing stones often (several times a year!) would be a significant bother and expense, it’s less of an issue with home saunas.

Other pluses — ceramic rocks weigh much less and are said to heat more quickly.

A caveat — people might stack them too closely, leaving too little space for air to circulate, and possibly wearing out the heating element prematurely. It’s more economical to replace the rocks than the heater. And, manufacturers recommend certain rocks for particular stoves — so stick with what they suggest.

The website writer at Sauna Site theorizes that hollow stones would be the best for a single set of bathers. He wrote, “A hollow stone gives up all of its energy, retaining none when the sauna-bathing is over [whereas] stones with a large energy-storing capacity and all large stones retain a lot of energy after a sauna-bath.” Hmmm.

Do you have experience with ceramic rocks? Please comment — I’d like to learn more, and so probably would other readers. 

Thursday, April 10, 2014

A short course — sauna stones 101

April the (unofficial) Month of Sauna Stones

Rocks matter. Heres what I learned from Lowell, my geologist friend, and two Internet sites, Rock Collector and Visit Sauna.

The qualities important in sauna rocks are durability (how quickly stones degrade) and thermal conductivity (how long they hold, conduct and radiate heat).

All stones eventually crumble (“friable” is the geological term) and fluctuating temperatures and water speed that process, so rocks in a sauna stove artificially weather even faster than they do in nature. That decreases their durability.

Since metamorphic and sedimentary rocks degrade more quickly than igneous rocks (those created by vulcanism), enthusiasts have preferred igneous rocks, like granite. Granite, however, can crumble at as low as 300 degrees Fahrenheit, a temperature not uncommon in the sauna stove (not the air surrounding).

Stones that best withstand the repeated temperature extremes of the sauna are those least exposed to weather — quarried from deep down where lava never reached the earths surface. (Geologists call them “plutons.”) Stones with iron and magnesium will conduct heat more efficiently and last longer. Quarried stones have more surface area than rounded rocks, thus more places to emit heat.

Peridotite, quarried in Finland, and olivine are dense, granular, igneous rocks, dark and heavy. They are among those with the highest thermal capacity. Others include plutonite, vulcanite, diabase, black basalt, chrome ore and diorite minerals I’m quickly becoming familiar with. 

Conecting technology to geology is the subject of my next post.


Friday, April 4, 2014

Rocks of ages

April the (unofficial) Month of Sauna Stones

My dad, Ben Rajala, told me the legend that opened Chapter 15 (Sauna Stones: Rocks of Ages) in my book, Some Like It Hot: The Sauna, Its Lore and Stories. It goes like this:

To be used in a Finnish sauna stove, he said, stones had to withstand eons of being rolled in the icy northern waters and further shaping by the ups and downs of temperature changes.

Then, the final touch (and his favorite part) every thousand years, great birds would wake from their sleep and flock to those northern shores, seeking stones on which to sharpen their beaks. After their intensive rasping, the rocks became rounded.

For their sauna stones, early immigrants to northern Minnesota used roundish ones, found on lake shores or riverbanks. Or maybe, when their farmland “sprouted” its spring crop of rocks, the family picked the biggest ones for their sauna.

For some, sauna rocks have special meaning. A couple I met chose stones that fit in their luggage when traveling around the world in Alaska, Spain, France, Turkey, Egypt and Antarctica.

How did the stones in your sauna come to be there?

Stay tuned for — a lesson in geology.


Wednesday, April 2, 2014

Why saunas need stones

April the (unofficial) Month of Sauna Stones

You might think of a sauna as a room lined with clear wood paneling and tiers of benches or a room that is heated to (uncomfortably) high temps. While both are true, neither defines the core of a sauna.

Actually, the sauna is the container for hot stones. Its stove is meant not to heat the sauna but the rocks. Surprised??

Without its stones, sitting in a sauna would feel more like being in a toaster. Rocks store heat and distribute it evenly, keeping the sauna hot longer. Plus the rocks provide surfaces for water to hit and make momentary steam the löyly. The hotter the stones, the faster the water evaporates.

The oldest Finnish saunas, smoke saunas or savusaunas, needed the heat-retaining capacity of massive stones because people hadnt yet invented a method for continuous heating. A fire lit underneath an arch of huge rocks burned for hours, all the while heating those rocks sometimes to red-hot. The radiant heat lasted for many more hours, through several rounds of bathers. 

This photo of the savusauna in the Cokato Historical Society Museum of Cokato, Minnesota, gives an idea of the size of rocks that were sometimes used. 

In modern saunas with electric stoves, that energy-storing capacity is less critical. The heating element stays on to heat the sauna and during the bath. We dont have to save heat” for the next bather, as Finns did long ago. But the heat radiated by the rocks makes our saunas so much more pleasant.

Next discussion: Why rocks were chosen, by legend, by sentiment and any other reason.  


Tuesday, April 1, 2014

Yes! A whole month on rocks

Drum roll...

This month, I’ll take on the topic of sauna rocks — which stones we use today, those preferred by early sauna-goers and why some are better than others.

Really, it’s no April Fool’s joke. I dub April the (unofficial) Month of Sauna Stones.

We’ll start with why rocks were important in the original saunas.