I have read on Wikipedia that beer is a really ancient beverage brewed many millenia ago. However, thermometer is only several hundred centuries old, and electricity is an even newer invention.

How is it possible to brew beer without thermometers and electric heating elements (or gas stoves)? My opinion is that both are really necessary. Without a thermometer, you cannot know the temperature of mashing. If the temperature is too high, you have too much sugars that are not fermentable, and if the temperature is too low, the beer will become too dry. All of this, of course, assumes that one has approximately the correct temperature for the enzymes that convert starches to sugars. It is very hard for me to understand how one could have the temperature even approximately correct, because the mashing temperatures are so high that feeling the temperature with your fingers is not possible. So, my intuition is that without a thermometer, even converting the starches to sugars should be very hard.

Similarly, if you don't have electric heating elements or gas stoves, it is almost impossible to control the rate of heating. With heating being done by burning wood, the control is very crude and the time constants of control are long. So, even if thermometers had been available in ancient times, controlling the temperature of the mash would be very hard.

The part of boiling, of course, is easy because water in liquid form cannot exist above 100 degrees Celcius. Chilling the wort might be tricky, but there is plenty of evidence that even the "no chill" method can work. Fermentation temperature control obviously requires a solution, but fermentation temperature is not as critical as mashing temperature, and fermentation temperature can be approximately measured by feeling the temperature with your fingers.

Has anybody here brewed beer without measuring the mashing temperature and without using a temperature-controlled oven? If so, did it go well?

  • 2
    Probably trial and error at first, then just following patterns that worked. Honestly, ancient civilizations had a lot more impressive accomplishments without modern technology than just brewing beer .
    – valverij
    May 16, 2016 at 20:56
  • 1
    And keep in mind that beer back then was very different than what we think of as beer now.
    – Denny Conn
    May 17, 2016 at 18:38
  • How do we know what beer was like back then? Anyone tried a bottle/jar? Jun 5, 2017 at 7:09

3 Answers 3


It's simple - experience. Brewers practiced under more experienced brewers. After few years, they could tell by hand - literally - if temperature is right, and they could taste if it's as sweet as it should be. That was how mashing was done.

Mashing temperature is actually low enough to put your finger in. I can keep my finger in mash for about 4 heartbeats at about 62°C, and two at 72°C. Not even one at mash-out. And in old times mashing was done in wooden barrels or clay pots, too. Temperature on the outside was raising significantly slower, thus easier to correct. last but not least, one could always learn to do things "by the rote" - "for one pot of malt, use three barrels of boiling water and half of a barrel of spring water", things like that. It would give pretty consistent results, at least at given month in given location. But as you probably noticed, some beers are even named after months, so that's not unlikely. Only brew märzen in March and you do not need any corrections for water temperatures etc, once you know proportions, you can use them each March.

For the rate of heating, why, of course they didn't. You might want to read about decoction mashing. It is considered more difficult now, but before we got that control, it was easier. Main mash tuns wasn't heated at all for the most part of beer history. And of course simpler styles used single-temperature mash.

Fermentation temperature control was trivial. You knew which beers you wanted to brew when and where. This one only in March. That one only in December and October. And that one needed to be fermented in this convenient cave. And that was all to it.

Chilling is trivial. Once the beer no longer any warm to the touch, it's safe to pitch. And in case of wild yeast fermentation, you didn't even need to bother. It was "pitched" all the time, so when it cooled enough, it got it's yeast.


In decoction mashing you don't need neither thermometers nor clocks.

You keep you main mash in one container. To increase the temperature, you take some of the mash into a different vessel and bring it to a boil. You can easily tell when it's boiling without a thermometer. You put that boiling mash (the decoction) back into the main vessel to raise the temperature.

Depending on how often you do this you have 1, 2 or 3 step decoctions. Depending on the number of decoctions and what temperature you want to reach, you take more or less to boil.

Decoction mashing had other advantages, most of which aren't a problem these days:

  • You could use a cheap wooden vessel for the mash and a more expensive copper vessel for boiling the decoction, hence equipment was cheaper.

  • Because you boil the decoction for some (15 to 40) minutes, you get more out of the malt (higher efficiency), especially with poorly modified malts.

  • When specialty malts (roasted malts) were not available, you could get a more grainy roasted flavor from decoction mashing.

As far as chilling the wort goes, you just let it sit. Some homebrewers still do this these days. It works quite well if you make sure the bucket is sealed so nothing gets in there.


Other answers are pretty complete. Basically trial and error, decoction allowed for step mashing.

More interesting is that yeast wasn't known yet. Family's would have a "stirring stick" that would be passed down generations, it's speculated that this stick would harbor the yeast and inoculate the beers aside from spontaneous fermentation. Giving each family their signature beers. Thier process regarding temp control would also be very guarded.

  • You should specify a time frame here... there was the medieval job of the Hefner (from Hefe, German for yeast) till 19th century. A Hefner would grow yeast and sell it to brewers. Unfortunately, I did not find an English source. de.wikipedia.org/wiki/Hefner
    – Robert
    May 18, 2016 at 14:44
  • @Robert idk, I think this would have been violation of the 1516 German beer purity law. As it was only revised after Pasteur discovered the microorganisms role in fermentation over 200 years later. May 19, 2016 at 3:18
  • Well, it was the Bavarian Purity Law, or even limited to cities. Until Bavaria joined what is now Germany, there was no German purity law. It also wasn't revised: the current German law that was based on the purity law includes yeast, but the old law remains untouched. It also regulated the price of beer, btw, which clearly nobody adheres to. That said, why would it violate the purity law if the yeast was brought in by somebody else?
    – Robert
    May 19, 2016 at 3:24
  • @Robert the original law didn't allow yeast as an ingredient as it wasn't known. It would make since that they figured out how to utilize beer trub, with consecutive batches. But I would question the role of a hefner witingly delivering fresh yeast to breweries. 1. There were places for food and drink more of a lodge than a brewery, and they were considered unique to each other as the quality of beer doubt they did much sharing of secrets. 2. Your source calls this profession extinct, seems it would have grown after Pasteurs discovery not died out. It's hardly extinct... White labs. May 19, 2016 at 14:22
  • Fascinating. Given the pitching rates for yeast that we aim for these days, I wonder how the Stirring Stick ever had enough yeast on it? Perhaps the old wild strains of yeast reproduced more prolifically once in the wort? Jun 20, 2016 at 21:21

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