With at least 4,500 small breweries dotting the Irish landscape, you might be tempted to call this the Golden Age of Irish Brewing, but all this brewing was taking place around 2500 BCE, in the Bronze Age. At least that’s a new theory being proposed by the Moore Group, whose ideas will be published next month in Archaeology Ireland.

Other suggested uses include for bathing, the washing and dyeing of cloth, metalworking, tanning and leather working. In any event, the sites are almost always found near of source of water. The way it was believed to be used was that the trough would be filled with water and then heated stones dropped in to quickly bring the water to a boil.

Billy Quinn and Declan Moore, two archaeologists from Galway, puzzled over this enigma until, nursing a hangover one morning, pondered “the natural predisposition of all men to seek means to alter [their] minds” and wondered if perhaps the Fulacht Fiadhs might have served a very different function. After doing some intensive research around the world on the habits of Neolithic man, have concluded that the Fulacht Fiadh’s primary use may have been for brewing, though they believe it may also have had other secondary uses and functioned much like the kitchen sink.

To prove their theory, the pair had to recreate the process that early Irish people would have used to brew their beer. So they set up an experiment using as close to the original method as they could to try and brew some Bronze Age beer. Here is a summary of that experiment.

The experiment was carried at Billy’s home in Cordarragh, Headford, Co. Galway. Seeking authenticity in replicating our Bronze Age ale we decided that our equipment should be as basic as possible. The wooden trough, posthumously donated by Billy’s granduncle, was 60 years old, leaky, wedge-shaped and measured 1.7 m in length, 0.7 m in width with a depth of 0.65 m (roughly consistent with the average trough dimensions from excavated examples). When filled with water to a depth of 0.55 m, it held 350 litres. After digging a pit, the trough was lowered into the ground and water added. Despite some initial leakage we eventually reached an equilibrium in the water level by simply flooding the immediate area. For the purposes of our experiment we sourced granite and sandstone from Connemara.

The stones were heated in a fire for roughly two hours. Step one involved transferring the heated stones into the trough using a shovel. After 15 minutes we achieved our optimum temperature of 60-70c. At this point we half submerged a wicker basket in the trough and began to add our barley in small amounts to prevent the mash from congealing. Over a period of 45 minutes, maintaining a fairly constant temperature with the addition of occasional heated stones (some of which were recovered from the trough and reheated) our water transformed into a sweet, syrupy, workable wort.

After converting the starches to sugar, ascertained by tasting the mash, we brought the mixture to a boil to sterilise it and simply baled the final product into fermentation vessels. We used spigoted plastic containers with a total capacity of 75 litres. Including the leftover liquid we could easily have produced up to 300 litres of wort. At this point we added flavourings, the majority of which were growing around us in Billy’s garden. These additives were ground in a mortar, wrapped in muslin and suspended in the top of our wort. We added 150 ml of brewer’s yeast after cooling the vessels in a bath of cold water for 3 hours.

We produced what is more properly termed a gruit ale (gruit is a term used to describe the herbal mix used to flavour ale). Through our experiments, we discovered that the process of brewing ale in a fulacht using hot rock technology is a simple process. To produce the ale took only a few hours, followed by a three-day wait to allow for fermentation. Three hundred litres of water was transformed into a very palatable 110 litres of ale with minimal work.

At the end of the process they were pleased with the results. “It tasted really good,” Quinn said. “We were very surprised. Even a professional brewer we had working with us compared it favorably to his own.” The beer itself is said to be a “cloudy, yellowish brew with no discernible head with a yeasty taste reminiscent of weiss beer.”

Here’s the basic recipe for Bronze Age beer:

1. Hot stones rolled through grain to malt it.
2. Grinding of malted grain.
3. Rocks heated on fire.
4. Heated rocks transferred into water in a fulacht fiadh trough.
5. Malted grain in wicker baskets plunged into water heated to 67° C (153° F).
6. Mixture stirred to break down starch into sugars that will react with yeast to form alcohol.
7. Mixture spiked with local ingredients such as bog myrtle, the hop-like bog plant, heather, elderflower, juniper berries and honey.
8. Mixture baled into fermentation vessels, which are cooled in running water before yeast is added.
9. Leave for three or four days to ferment.
10. Drink.

The Moore Group has an extensive photo gallery of the experiment and has posted a video on YouTube of the experiment:

Fascinating stuff. I’d love to try some of that.