Sahti Feb 26

Sahti

HL Marcello Fornarius
for Summits A&S (Feb 14, 2026)

Introduction

The surviving tradition of farmhouse brewing in the Nordic countries traces its lineage from the primary way of brewing in Europe in the first millennium - before brewing became a profession and hops were introduced to the process. The modern drinks sahti, koduõlu, gotlandsdricke, maltøl, and kaimiškas from the area around the Baltic Sea are all examples of farmhouse ales - sahti is merely the most famous. These farmhouse ales could be brewed for everyday drinking with low alcohol content (AC), or for feasting with higher AC. Sahti is typically a feasting drink, with an AC from 5-9% which is similar to modern microbrews. My main resource for this project is Viking Age Brew: The Craft of Brewing Sahti Farmhouse Ale by Mika Laitinen (2019). 

Archeological evidence for brewing is scarce, because vessels made of wood and organic remnants like malt don’t survive well. However, the oldest evidence of fermented drinks in Europe is found in Scotland and dates back five thousand years. As of 1500 BCE, mixed brews started to spread across the Nordic area.

The technology needed for ale brewing includes large vessels, water heating, casks, malting, which all have evidence in period. The fashioning of large wooden barrels is at least 2000 years old, and these wooden vats would have been more common and cost effective for non-professional brewers than ceramic or metal vessels of any size. Malt is germinated grains which are dried for longer storage. The technology of malting originated in Egypt and Sumer, and was well known throughout Europe. Due to the climate, northern malts used for sahti would have been dried over fire or in a smoke sauna, unlike Egypt, where they were likely sundried. 

Homebrewing traditions on which modern sahti is based diverged from professional brewing in the 13th Century, with the archaic brews only surviving in remote areas. Professional brewing innovations included wort boiling and hops, which are not present in traditional sahti preparation. Some forms of traditional sahti preparation survived in remote Finnish areas until almost World War II. 

I have been making sahti for about 3 years, gradually adding more historical tools. 

Glossary

Lautering: the process where wort is drained from the mash

Malt: grains in which enzymes have been activated in order allow for fermentation

Mash: malt mixed with hot water

Sparge: rinse malt grains with clear water to get more malt sugar into the wort

Wort: malt-sugar filled liquid

Kuurna: (Finnish) large lautering tun, often made from a hollowed out trunk - ash or pine wood are popular.

Traditional Ingredients

Malt

Barley and rye, soaked for 1-3 days, then dried in a barn or sauna, including hot smoke. Crushed in a quern. (Sometimes supplemented with unmalted grain.)

Yeast

Yeast would be transferred from a previous batch using a birch whisk, wooden ring, or bit of previous brew saved in a jar down a well. 

Herbs 

Common (Eurasian) Juniper to clean vessels and filter wort. Hops are not common in modern Sahtis, tho they were grown as early as 1000CE, perhaps for dyes or rope making and are difficult to find record of in historical sahti. 

Water 

Perhaps when heated with rocks from a firepit, the water may have had more minerals in it, tho excess sediment could be filtered out during lautering. Modern Finland’s water is high quality with low mineral content otherwise. 

My Ingredients

Malt

Commercially purchased barley malt (Vienna and Munich this time) plus a small amount of Crystal Rye malt, mechanically crushed at the brew supply store. 

Yeast

I saved a jar of yeasty sediment from my previous experimental batch in the fridge; I had used Red Star baking yeast the previous batch. 

Herbs 

I use purchased juniper berries in small quantities to simulate Juniper taste, since American juniper is a different species and is sometimes poisonous. I sometimes use raspberry canes in the filter (tho not this time). 

Water 

I use tap water, starting with water hot from tap. When I add extra water as needed - usually during sparging, but sometimes I estimate wrong at the beginning - I now heat it to specific temperatures using my electric hot water kettle. 

Traditional Process

Sanitation: 

Cleaning wooden vessels with hot juniper infused water. This water could be heated with hot stones in the vessel itself. 

Mashing:

A long, slow, process of raising the temperature of the mash by adding gradually hotter water - starting with lukewarm, hot, then nearly boiling water - letting it rest for an hour +/- in between. In period, the wort would not have been boiled, an innovation from the Enlightenment Era. 

Lautering:

Juniper twigs and straw would be used to cover the hole in the kuurna, so the mash does not go into the fermenting vessel. 

Fermentation:

Yeast was added when the batch was about body temperature.

Maturation:

Once the primary fermentation is complete, the sahti is transferred to a cask and set to a cold storage place/cellar for a few days. 

My Process

Sanitation: 

I use commercial high powered sanitizers  - phosphoric acid (StarSan) - on some of my gear, including airlocks, glass carboys, siphons, and the hydrometer. The kuurna gets rinsed hot in the shower tub, and the plastic buckets I use for sahti have been given over to traditional fermentation, so have residual other microbes. While I imagine that some of the microbes in the kuurna get killed by the heat of the initial mash, there’s no way to fully modernly sanitize the wood, and the wood’s microbes add to each brewer’s  particular flavors. (I also sometimes use my kuurna to process grapes for wine, so it certainly would have some wild yeasts from that as well.)

Mashing:

Since I’m using a steel kettle on the stove instead of a wooden kettle that can’t go over a fire, I add all my water at the beginning (tho I would like to try the other version next time). Starting with bath hot water shortens the process of heating the water enough to get started. I then heat the water to about 140F (determined using an electric meat probe thermometer) before adding the crushed malt. I then lower the heat on the stove and leave it for 45 min. This time, I put the grains straight into the pot, and stirred occasionally. After 45 minutes, I added 5 juniper berries to simulate some of the flavor that one would get from using juniper in the sanitation process, and raise the heat to about 158F. After another 45 min, I raise the heat to 176F and let it go for 15 min. This is based on Laitinen’s homebrewer’s sahti (p 203), and allows me to only take a morning instead of all day to brew. 

While sometimes my mash gets hotter than the target temperature, I don’t do a full boil, so - as with traditional sahti - it should be drunk within a week or so.

Lautering:

This time, I used hop bines to help keep the malt out of the bucket. This is only partially successful, even after I changed angles and used a ladle to help, so I will make an effort to save straw next season. The extra sediment can be filtered out at a later step. 

I sparged the mash with an extra 2 litres of water, part at 185F and part at boiling. In the process of trying to keep the mash out of the fermenting bucket, I circulated the wort over the mash in the kuurna 5 or 6 times, with the additional bonuses of both rinsing more sugars out of the mash and helping cool the wort. I was in a hurry, so I didn’t save the mash for bread or make a second run.

Fermentation:

After lautering, my thermometer read 105F. I added my yeast and then put the airlock on and wrapped the bucket in our heated blanket and let it go for about two days - enough time for the yeast to work. 

Maturation:

I transfer my sahti to growlers, but leave the airlocks, and put them in the laundry room. This time of year, it is reliably 50F or colder. The sahti continues fermenting at a slower pace. I usually time my brew to be a week (or two at most) before I intend to share my brew. The increase in time helps the yeast settle and the flavor to smooth out. Heirloom yeasts may settle out of the ale solution faster, but I do use a modern yeast (I don’t have a heirloom Scandinavian sourdough starter). This year it will be about 2 weeks. Close to the event I move it to the fridge to make sure the fermentation has stopped. 

 Things I have learned through various batches: 

• Sahti is easier to make in winter when the laundry room is cold. For secondary fermentation, either it takes up a ton of space in the fridge or the cooler isn’t tall enough for airlocks and costs for ice. 

• The kuurna doesn’t need to be at a steep angle for fluid to drain, and less mash gets in the bucket at a flatter angle.

• Doing several repeats of lautering the wort thru the kuurna reduces the temperature to yeast friendly pretty quickly, even on a temperate winter day. 

• Straw is the best filter. Raspberry and blackberry canes work ok, but if I’m using the brew bag, they tend to catch on the mesh. 

• Using hot stones to heat water does change the taste, but a steel kettle doesn’t hold heat as well as the traditional wooden one. 

• My seven gallon brew kettle (that is designed for a 5 gallon modern extract brew), holds about 2-3 gallons of whole grain mash comfortably when wet. I can even get a wooden spoon to reach the bottom. 

Things I still want to try:

• Heating water with rocks on a full batch. Is there a difference between heating the rocks with fire or in the oven? (What flavors come from rocks versus fire?)

• Raising the temperature of the brew by adding water (instead of adding most of the water at the beginning) - Now that I have a better idea of what size batch fits in the kettle, I think this is possible. I would still probably need to insulate the steel so that the brew doesn’t lose heat too fast. 

• How much of a taste difference would fermenting in wooden vessels provide?

• Using actual eurasian juniper branches as filter and/or cleaner

• Malting my own grains (this has failed and molded in the past)

Resources: 

Laitinen, Mika. Viking Age Brew: The Craft of Brewing Sahti Farmhouse Ale. Chicago Review Press, 2019. 

History of Malting: https://www.brew.info/a-journey-into-the-history-of-malting/ and https://the-past.com/feature/from-brewing-to-bread-exploring-the-buildings-of-the-british-malting-industry/ 

Conversation and advice from Otto Gottleib (techniques) and Phillip de Greylonde (yeast)

Kuurna made by Ulf the Wanderer, wooden spoon decorated by Gwyneth Blackthorne