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By Paleorama
Few things delight archaeologists as much as piles of rubbish from hundreds of years ago, because the old bones and stones found in waste heaps can tell complex stories.
And in central Norway, the story they tell seems to be that the Vikings and their descendants brewed beer by dropping hot rocks into wooden vessels.
The History of Norwegian Farms
Much of the story of how Norwegian farms were founded and developed over the millennia is still a mystery.
Geir Grønnesby, an archaeologist at the University Museum of the Norwegian University of Science and Technology (NTNU), puts it this way.
There are a lot of these stones, and they turn up at most of the old farm sites.
Grønnesby is fascinated by the history of Norway’s farming settlements, and he has good reason to be.
The reason is simple. Most archaeological digs are tied to construction projects, because developers are required to check for cultural remains before they start building.
It is rare for a developer to run a road or some other large project through a farm, which means farms are rarely excavated by archaeologists.
Most of the archaeological information we have about the Viking Age comes from graves, and most of the archaeological information about the Middle Ages comes from excavations in towns. Most people lived in the countryside.
Basically, Norwegian farms sit on top of a huge underground treasure that in some places dates back to 600 AD, toward the end of the Iron Age, and most of it remains untouched.
So I started doing these small excavations to look for archaeological layers on old farm sites. The oldest carbon 14 dates I have found are from 600 AD, and all the dates are from then or later. And then I found the stones and had to write about them, because there are so many of them.
Hot Rocks for Brewing Beer
Grønnesby was not the first to notice these fire-cracked stones on the farms of central Norway.
That honor goes to a pioneering sociologist named Eilert Sundt, who recorded an encounter on a farm in Hedmark in 1851.
As Sundt would later write, he was out walking when he saw a farmer next to a pile of odd-looking small stones and asked him about them.
What are these stones from?
The farmer answered with these words.
They are brewing stones. Stones that were used for cooking and brewing Viking beer, back in the old days when they had no iron pots.
In his article, Sundt noted that most of the farms he visited were surrounded by piles of burnt or fire-cracked stones.
Every time he asked about them, the answer was the same. They were for brewing beer, when the stones were heated until they were “red hot” and then dropped into wooden vessels to heat the liquid.
The stones were so common, Sundt wrote, so plentiful and packed together in some places, that houses had been built right on top of them.
Reports from archaeologists who have studied farms in recent times also back up this observation.
When an archaeologist dug a test pit on a farm in Steinkjer, north of Trondheim, in the 1980s, he found an archaeological layer more than a meter thick, made up mostly of fire-cracked stones.
Grønnesby himself excavated more than 700 cubic meters of stones in one section of a farm in Ranheim, also north of Trondheim.
And when Grønnesby sampled 24 farms, 71% definitely or probably had layers of fire-cracked stones.
An Ancient Viking Tradition
It is not so strange that the Vikings brewed beer with stones, Grønnesby says, since the same process has been recorded in England, Finland and the Baltic.
The tradition lives on in Germany, where you can still buy “stone beer” today.
German Steinbier was revived in 1982 at the Rauchenfels brewery in Neustadt bei Coburg, after decades without commercial production, and today it is brewed by Leikeim in Altenkunstadt, in Upper Franconia (Craft Beer & Brewing).
In Norway, the Gulating, a Norwegian parliamentary assembly that met between 900 and 1300 AD, regulated even the smallest details of how beer was brewed and drunk at the time.
The Gulating laws required three farmers to work together to brew the beer, which had to be blessed.
Anyone who failed to brew for three years in a row had to hand over half of his farm to the bishop and the other half to the king, and leave the country.
Only the smallest farms were exempt from this strict rule.
Just as interesting is the moment when brewing stones vanish from the archaeological record, around 1500 AD, right at the time of the Reformation.
Grønnesby offers a few possible explanations.
It could be a strange coincidence. It could be because of religion. Or it could be that iron pots were easier to get hold of by then.
From Rubbish Heaps to Archaeological Treasures
Every time a red-hot brewing stone was dropped into a cold container or liquid, it cracked.
After several of these cycles, the stone would be too small to keep using, and the brewers would toss it onto the rubbish heap.
That means the thick layers of stones also contain other objects, such as old spindle whorls and loom weights, animal bones and beads.
That is why the stone deposits matter, as much for what they hold as for the stones themselves, Grønnesby says.
Archaeologists are always finding these deposits, but they used to look at them and scratch their heads, and the deposits did not get the kind of attention they deserved. These deposits are archives from the Viking Age through the Middle Ages, so we should be excavating them more often.
Grønnesby’s research is included in the book “The Agrarian Life of the North 2000 BC to AD 1000“, published in 2017.
Grønnesby’s chapter is titled “Hot Rocks! Beer Brewing on Viking and Medieval Age Farms in Trøndelag“.
Frequently Asked Questions (FAQ)
1. How did the Vikings brew beer with hot rocks?
They heated stones in the fire until they were red hot and dropped them into wooden vessels holding the mash, which could not be put directly over the fire. The heat from the stones raised the temperature of the liquid and the thermal shock cracked them, so after several uses they ended up in piles next to the farms.
2. What archaeological evidence is there for this technique in Norway?
Archaeologist Geir Grønnesby, of the NTNU University Museum, found definite or probable layers of fire-cracked stones at 71% of the 24 farms he sampled in central Norway. On one farm in Ranheim, north of Trondheim, he excavated more than 700 cubic meters of these stones.
3. When did people stop using brewing stones?
They disappear from the archaeological record around 1500, close to the Protestant Reformation, which reached Norway in 1537. Grønnesby suggests the cause may have been religious, or that iron pots became easier to obtain at that time.
4. Is beer still brewed with hot rocks?
Yes. In Germany, Steinbier was revived in 1982 at the Rauchenfels brewery in Neustadt bei Coburg, and today it is brewed by Leikeim in Altenkunstadt. In modern versions the hot stones are lowered into the wort, unlike the historical method, which dropped them into the mash.
5. Where was Grønnesby’s research published?
In the chapter “Hot Rocks! Beer Brewing on Viking and Medieval Age Farms in Trøndelag”, part of the book “The Agrarian Life of the North 2000 BC to AD 1000”, edited by Frode Iversen and Håkan Petersson and published in open access in 2017 by Cappelen Damm Akademisk.
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