Sunday, 28 December 2014

What is Wort - a brewer's perspective

Hope you had a grand Yule and that you enjoyed the midwinter celebrations. We wish you all the best and A Happy New Year for 2015. There has been a bit of a lull on ancient ale blogging in the last couple of months, however we aim to correct this in the New Year and get back to writing again.

This one is about the Wort. Graham wrote it several months ago. It would make a good response to a short article "Beverage with heritage" that we read over the holidays. It was published in the Christmas and New Year Edition of New Scientist magazine, the 'one minute interview' with Patrick McGovern, director of the Biomolecular Archaeology Project for Cuisine, Fermented Beverages and Health at the University of Pennsylvania Museum. The question is asked: how does ancient booze compare with the modern stuff? The answer includes that "they wanted to be sure they had enough sugar to get the fermentation going, so they took whatever they had that contained sugar and mixed them together."
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This idea of 'mushing loads of random sweet stuff together to make alcohol in prehistory' seems to be a commonly held view amongst non brewers. Merryn wrote a blog about desperately seeking sugars a few months ago, which tried to address the issue and dispel this myth.

Here is Graham's perspective, a beer brewer's explanation of what wort is:


Wort (pronounced wirt, not wart ) is the Juice of the Barley, well not quite, but almost very nearly so. It is a thin, runny, very sweet but very sticky liquid, straw coloured through to brown. It is effectively a thin synthetic honey substitute. Ale made from wort without preservatives or flavouring actually tastes a lot like mead made from honey.

Wort is the liquid sugars extracted from malt, that is to say, partially germinated cereal grains - barley, wheat of all varieties, oats and even millet, but not rice or maize. It is the primary source of fermentable sugars in making ale or beer and always has been. It is relatively easy to make a sugar solution of at least 10% from malt, and then to wash further sugars from the grain down to a realistic level of 1-2%,  "small beer" level and, of course, anywhere in-between. This compares very favourably with other natural sources of sugar like birch sap, which is between 0.5 and 2% sugar, which would only make a small beer. So adding birch sap to a brew would only dilute it, not strengthen it as some scholars claim.

Wort is made by "hijacking" some of the natural processes of the grain's life cycle.

As part of the growing process the germinating grain must convert it's energy store, starch, into sugars so that these can then be built into cellulose, the structural skeleton of the roots and shoots. This requires the liberation of the two amylitic enzymes, alpha and beta, which are little like ptyalase, the enzyme in saliva that converts starches into sugars.

If this growing (germination) process is halted when the most enzymes are present and little of the growing structure has started, it will be good malt.

So, to make wort you lightly crush the malt and mix it with hot water at about 65 degrees Centigrade. Keep it at this temperature for anywhere between half hour to about 2 hours, depending on your style. This is called mashing. Then you drain the clear liquid sugars from this mash by lautering, which is yet another story. This gives you a strong wort. Then you can wash further sugars from this mash, sparging, to get a weaker wort.

Brewers measure the potential sugar and therefore alcohol of a wort using "specific gravity". Water is 1000. David Line in his book "The Big Book of Brewing" explains this in great detail in chapter 18.

This was my "Bible" when when I first began brewing beer 32 years ago. David Line was a pioneer in his time, explaining what the processes were, how they were done and why. He also explains different methods of mashing using simple equipment and this has been very valuable to me in re-creating the ancient and traditional crafts of brewing ale.

So to recap: wort is a golden brown, very sweet, very sticky, runny liquid that contains most of the potential sugars from the malt. It can be made to a variety of strengths e.g. Arctic Ale.

To illustrate this I will give you the results of one of my recent brews.

The recipe is loosely based on David Line's "Brewing Beers Like Those You Buy" page 88, Gales HSB. One of my favourite beers, sadly no longer made. I found his book to be an excellent collection of recipes for good Ales and Beers that could be bought in the late 1970s and 80s. Large brewery's methods have changed since then and sadly many of the modern renditions taste nothing like they used to.

15lb 8oz of crushed pale malt, Munton's Perl Blend, were mashed with 5 gallons of water, inside a grain bag, in a Peco Electrim mash-tun. The strike temperature was 70 degrees Centigrade and as the grain was added slowly, the temperature fell to about 60 degrees Centigrade, and was then raised back to 65 degrees Centigrade.

The mash tun was unplugged and covered with a sleeping bag to maintain the mash temperature. It was left like this for 2 hours.

From this I lautered 3.5 gals of wort which was nearly 1080OG.

wort: the first running
measuring the first running
























This was followed by sparging. The first gallon of wort was 1062OG, the second 1048OG, and these, together with the 3.5 gallons, were boiled in an Buffalo 40 litre boiler with 1lb of dark soft brown sugar, and 4oz of molasses (these are the in the recipe and I think the molasses adds a certain something to the flavour) for one and a half hours. This produced 5 gallons of 1084OG. This was fermented in two fermenters.


A further 5 gallons of wort were sparged of 1036OG, 1020OG, 1012OG, 1006OG (this was very pale and weak) and finally 1014OG left to drain overnight. This was again boiled on the old hops, because there is an awful lot of sugars left on the hops. This gave 5 gallons of 1024OG, which was added to the two fermenters. At the end of primary fermentation this gave 10 gallons of 1008 final gravity.

The average of 1084 and 1024 gives an OG of 1054 for the 10 gallons. According to David Line's graph (on page 147 Big Book of Brewing) gives a strength of 7.5-1.1= 6.4% alcohol.

This was quite a surprise to me, for I haven't been measuring the gravities for some time, and I never expected to get this much beer from 15.5lbs of malt.

A recent comparison with a commercial beer, Scapa Special 4.6%, suggests that my beer was no stronger, so maybe there is something wrong with my figures.

But it did make me think that I may be over-sparging my wort and that this could be contributing to the haze, and tannin like bitterness. So I have increased the malt to 17lb 8oz, and now I am getting a much nicer beer.

For those of you who will never meet malt, or a mash tun there is an alternative. Go to a whole food shop and buy one of these.


As best as I can estimate, this jar contains 11 fl oz of malt extract weighing 16oz, so this makes a density, specific gravity, or OG of 1450 or so. Dilute this with 4 imperial pints of water and you will have a re-hydrated wort of about OG1054.

Wort is a brown, runny, very sweet liquid that is extremely sticky when it dries. It could be described as a kind of dilute synthetic honey, that is very ancient in origin and is possibly the first process that was ever made with cereals. It could be that cereals were first cultivated, not for their staple qualities e.g. flour, gruel or bread, but instead for their status potential, sugars.

Many of the early settlements in the Fertile Crescent had special buildings with smooth floors, made of beaten earth, clay or lime plaster which are ideal as malting floors. All that is then required are containers within which to heat the crushed malt and water (the mash) to make a sweet wort. Merryn's M. Phil, entitled Barley Malt & Ale in the Neolithic (1999), looks at this, and the archaeological evidence for it, in some detail. One particular site, Beidha, was excavated in the late 1950s by Diana Kirkbride, a member of Robert Braidwood's team. She describes a smooth plaster floor with 'thousands of grain impressions'. This is probably a malting floor. The site is dated to the 8th millennium BC.

There is a Biblical expression: "The land flowing with milk and honey". Some Biblical scholars have made tortuous explanations to explain this phrase - they write about how wild bees' nests in cracks in the rocks would ooze honey in the hot sun. More informed scholars explain that this phrase refers not to bee honey, but rather to some kind of artificial sweetness, perhaps made from figs or dates, or maybe even made from grapes.

This must be because these scholars do not recognise nor do they understand that cereals can be a source of sweetness, if processed correctly.

I think that this phrase 'land of milk and honey' refers to milk and wort. It is a metaphor, or a description of a land that is good for both cows and for growing grain.

It seems that Biblical scholars have overlooked the fact that wort (liquid sugars made from the grain) was once commonplace in Egypt and Sumeria, otherwise they would not have been able to make beer. This was probably common throughout the whole Fertile Crescent and the Biblical Israel.

With the rise of Islam in this area, alcohol has been proscribed. There is no further use for malt or wort, so the practices and knowledge of malting and mashing have died out completely there. Archaeobotanists and archaeologists who have done field work on cereals in Turkey and the Ancient Near East seem to be unaware of the malting, the mashing and the wort. It is outside their experience and so it is understandable that wort has been overlooked in archaeological interpretation.

Today Bouza is made, it can be described as a type of beer, however it is a wheat based beverage made by lactic fermention. It is no longer alcoholic.

So, why do I bother to go to all the trouble of mashing, lautering, sparging, boiling and all that washing of brewing equipment? After all, it takes a whole day, a huge amount of effort. The answer is that all of the Beer Kits that I have ever used produce a beer with a kind of metallic flavour. The Kit contains a large can of Malt Extract. No amount of boiling with extra hops, or anything else will make it taste any better.

I make my beer with the simple, basic ingredients. I use traditional techniques to make the wort because I think it makes a better tasting beer. At least, when everything goes to plan, it tastes good. Even when it's bad it is often not much worse than some of the bad commercial beer available in supermarkets.

Beer is changing, with the way it is made. Some commercial beers, in cans, bottles and on draught have this unpleasant metallic flavour. They have been made from malt extract.

I was disturbed recently by looking carefully at the contents lists of commercial beers. Some like Scapa Special say that they are made from "maris otter pale ale malt", or others "a blend of pale and roasted malts". I know these are made "from the grain" and not with malt extract.

Some lagers and stouts are labeled as containing barley, wheat and oats, with no mention at all of the malt.  I can't help but wonder if they have been made from syrups, much like the high fructose corn syrup so popular in the processed food industry. This could explain the uniform blandness of some of these cheaper beers.


Saturday, 13 September 2014

grain dryers, malt kilns & "malting ovens"


I'm taking a look at "malting ovens" and malt kilns in this post. What are they, how do they work and do "malting ovens" even exist? There's been some news coverage recently about a rare and unusual archaeological discovery. It's a stone built structure, it's large and very few have been discovered in Britain. The feature that has been interpreted as a "medieval malting oven" in the centre of Northampton, dated to the 13th Century has even made it onto the local TV News. The local brewery is very keen to rescue it, rebuild it and install it at their brewery. So, it is rather important to understand exactly how it worked. 

Here's one of the most frequently used images of it, from the BBC news page report.

 Northampton malting oven

I'm impressed by the quality of the stonework. Whatever the function of this feature, it was very well built. It was heated by a fire on a regular basis, as can be seen from the blackened earth, in the entrance of the kiln.

So what was it? What kind of medieval industry would have used something like this? Was it a part of the malting and beer brewing process? Or was it something else?

For me, it's a frustrating picture. I want to see more of the context and the surrounding archaeology. I have lots of questions. Was any grain found nearby? If so, was it examined to identify partial germination, otherwise known as malting? If this was a malt kiln, which is of course a possibility, then where was the malting floor? And were there any steep tanks? Steeping facilities and malting floors - these are essential installations for the manufacture of malt. Without them, you cannot make malt.

To describe this stone built feature as 'a malting oven' is, however, not the correct technical name.

Within the traditional trade, craft and industry of malting, they are called malt kilns. Another description could be a grain dryer or corn dryer, used to dry the harvested oats and grain as well as to dry the green malt from the floor. It's an important point. If you don't use the correct terminology for a craft, then perhaps you are not familiar with the technical details and everyone gets confused. This applies to any craft, technology or skill based activity - when discussing or interpreting the archaeological discoveries that relate to it, the correct jargon should be used.

The only place I find "malting ovens" referred to is in the scholarly literature of archaeology, anthropology and history. An installation that has been interpreted and described as a 'malting oven' infers that the malt is actually made in the oven, that you can just put a heap of barley into an oven, heat it up and then, hey presto, you have malt. In many of the news reports about this particular medieval discovery in Northampton, there is someone saying that malt is made by 'roasting the barley in an oven.' It's a common misconception.

Here's a photo of an artist's impression of grain drying, from one of the information boards at Jarlshof, Shetland. This an archaeological site with evidence of stone buildings that span over 4000 years, from the Neolithic to the late medieval. The picture is supposed to illustrate 'how grain is dried in a corn drying kiln'. Every detail is wrong.

Not how a malt kiln or grain dryer works.
This is not how a grain dryer/malt kiln is constructed. It would not work. Why not?

- you can't dry damp grain or malt by heating it on a solid floor with a fire beneath. You will end up with hot wet grain.

- there needs to be a permeable floor for the wet grain or malt to lie on, so the warm air passes through the grain bed.

- the fire is not lit directly beneath, but at a distance. A long flue conveys warm air from the fire to the bowl of the kiln. The warm air rises through the bed of grain or malt, drying it gently and slowly.

- the reason for a long flue is to prevent sparks from the fire from setting the almost dry grain or malt alight. Malt kilns do not have a chimney, as this illustration shows. There is a wide opening at the top.

- it is essential to dry the malt slowly and gently over several days. The direct heat of a fire is too hot and would 'kill' the malt. Instead, you need warm air to dry the malt. 

Malt is not the same thing as roasted barley.
In the academic archaeological and anthropological literature, I have come across the idea that ale and beer can be made from roasted barley. Over the years, I have done lots of demonstrations about how the malt and ale are made and it seems that lots of people think this. Sorry to disillusion you, but it is not possible to make ale or beer from roasted barley. It can only be used as an adjunct, for flavour and colour. It is not a base malt and cannot provide any sugars in the mash tun because it has been roasted, thereby destroying the enzymes that convert starch into sugars.

In medieval terms, the germ of the grain has been killed by roasting.

Specialist malts, also known as coloured malts such as crystal, amber, roasted or chocolate malt, are a feature of modern, not medieval brewing. They have only been around since the early 19th Century. Specialist malts are dried or roasted at a much higher temperature than base malt and are used for the colour and flavour of the beer or ale. They do not provide any of the necessary fermentable sugars. That comes from the base malt.

Grain drying and malt kilns
There is another popular misconception. Because they are called kilns, it is often assumed that they have to be run at a high temperature, like a pottery kiln or a kiln for making bricks or roof tiles. This is not so. High temperatures kill the malt.

A typical grain barn is a long, rectangular stone building with a circular kiln at one end. The fire is lit in the fire hole and the warm air, and the smoke, travel through the flue and pass through the bed of grain which has been spread on a lattice of sticks in the bowl of the kiln. You would certainly not want to light any fire directly beneath that.
http://www.archhighland.org.uk/userfiles/image/sites/big/highland%20folk%20museum%20corn%20kiln%20grain%20platform.jpg
wet grain is spread out on a lattice of sticks, woven together.
see here for more details
It takes several days for the grain or malt to become completely dry. Here is a short video that explains how a grain drying kiln works, with "grain" including harvested grain or oats being dried for storage, and also malt, which is used for brewing. There is only one comment on the video, and that is by Martyn Cornell, the award winning beer writer, who makes the point that it is a maltings, not a corn dryer.

In an earlier post, I wrote about traditional grain barns and grain dryers and on how they worked, focusing mainly on the Corrigall Farm Museum, in Harray, Orkney. I'm really lucky where I live, because on Orkney there are quite a few surviving grain barns and grain dryers, some of which date might back to medieval times. Most are fairly ruined and none of them are used any more.

Graham took some photos of an old grain drying kiln at Houton, Orphir, Orkney a few years ago. We are not sure of its' precise age, but it is typical of many such buildings on Orkney and Shetland. We think they should be preserved and treasured as part of agricultural history.

the ruins of a grain barn, with kiln, at Houton, Orphir, Orkney. Photo by Graham Dineley

the barn is fairly ruined but the kiln is mostly intact - it's very well built

looking down into the bowl of the kiln, with the flue just visible on the left
looking up 

this is the stone 'shelf' upon which the lattice sits, the hole is where the dried malt is raked out
So, the more I think about that medieval "malting oven" recently discovered in Northampton, the more I wonder whether or not it was one. I leave it to the archaeologists who excavated it and to the brewers who aim to rebuild it in their brewery. Whatever they decide to do, some explanation of how it worked is needed.

I'll end this post with a ground plan, because all archaeologists like ground plans, of a traditional Orcadian farm house, byre, stable, grain barn and kiln, from John Firth's book "Reminiscences of an Orkney Parish". I hope it shows what I mean - that the kiln fire is not directly beneath the grain.


Monday, 18 August 2014

what's the archaeological evidence for malt?

This is something that I became more and more interested in, once I had completed and submitted my thesis. How does an archaeologist or an archaeobotanist recognise whether or not a grain is malted? What happens inside the grain on the malting floor? I had access to the University Library for a few years after my degree - by teaching archaeology classes in the Continuing Education Department. I explored sections of the Library that, perhaps, no archaeologist had visited before. I studied grain germination physiology, biochemistry and discovered that Bewley and Black's classic study of seed germination was the best.

Malting is an important craft and technology. The main reason for making malt is to brew with it, or more specifically, to make an ale or beer from the wort. Malt is also the main ingredient for whiskey, of course, but I am most interested in malt and ale in prehistory and its' role in the origin of grain agriculture. Apart from grain barns and malting floors, it seems that the best archaeological evidence for malt lies within the grain itself. There are clear physiological indications, depending upon whether the grain is desiccated (dried) or carbonised (charred).

Carbonised or charred grains are frequently found in archaeological excavations from the neolithic, when people first began to cultivate and process grain, right through to the medieval era and beyond. Carbonised grains are found all over northern Europe.

What do they signify?

Is it evidence of a grain store or granary that has been destroyed by fire? This was suggested in interpretations of excavations of an huge rectangular timber building at Balbridie, Fife, Scotland where thousands of carbonised grains were found?

Perhaps the grain dryer in a barn caught fire, while they were drying the harvested grain or oats. Or was it a kilning of the malt, which has gone disastrously wrong?

Lots of grain barns have burned down over the years, as well as traditional malthouses - it is not an unusual event. Even in recent times, as late as the 1960s, malthouses have been known to catch fire.

 http://digitalmedievalist.com/wordpress/wp-content/uploads//2014/05/barley-grains-ancient-celtic-beer-h-p-stika-300x188.jpg


These carbonised grains are from Eberdingen-Hochdorf, where there were the remains of Iron Age malting and brewing.


The Iron Age site was excavated by Professor Hans Peter Stika between 1989 and 1993. According to the excavation report, it was a high status site, probably the rural residence of a prince. The carbonised grains, a huge number of them, were found in a sort of U shaped ditch, together with bits of charred wood. The interpretation was that as the malt was being dried, the fire had got out of control and set fire to both the wooden platform upon which the malt had been laid, as well as carbonising all the malt. The charred grains were mostly barley. Many of them had missing embryos and the grain was in poor condition.

They were identified as having been deliberately malted using these criteria:
... groove like channels on the dorsal sides
... the dorsal side becomes concave
... the coleoptile and coleorhizae become more prominent
... germination roots develop
... separated or fragmented embryos
... germination was even, meaning that it was deliberate and intentional

A recent excavation at another Iron Age site has also identified the activities of making malt and brewing by examining the charred grain. Another accidental fire had preserved the malt as it was being dried in the 5th Century BC at Roquepertuse in south eastern France. The sample of grain was taken from the floor of a building, close to a hearth and an oven. The excavators describe it like this:

"In spite of favourable conditions for the preservation of seeds in the sediment, which was rich in ash, charcoal and generally carbonised plant material, the grains are corroded and highly fragmented. This fairly poor preservation seems rather specific to the barley grains from this sample. Conditions are therefore not suitable for a satisfactory observation of all the morphological features of most of the grains. However, the best preserved specimens allow the assessment that slightly more than 90% of the grains were sprouted when carbonised. This is easily visible from the groove like channel on the dorsal side of the grains. As far as we can see, the sprout length is not perfectly uniform, but it generally reaches about two thirds the length of the grain. 

The poor preservation of barley grains is probably caused by germination, which tended to render them brittle. Fragmentation occurred mostly after carbonisation and is therefore not due to Iron Age human practices." Bouby et al, 2011, Never mind the bottle. Archaeobotanical evidence for beer brewing in Mediterranean France and the consumption of alcoholic beverages during the 5th Century BC

It's beginning to get a little bit technical here and, perhaps, a good time to explain some of the grain germination jargon. There is a lot of it, so I shall stick to the basics. The fundamental biochemical processes and the physiological changes of grain germination occurred in ancient grains just as they do today, in modern grains. It doesn't matter whether you make malt 10,000 years ago or 5000 years ago or 10 minutes ago, the biochemistry of grain germination remains the same.

Grains are a lot plumper than they used to be, because of selection and development by farmers over the millennia. The aleurone layer, a special layer of cells just beneath the husk, is three or four cells in depth in modern grains, rather than the one or two cells in ancient grains. The structure of ancient cereal grains was studied by Professor Geoffrey Palmer, who looked at 3000 year old grain from Amarna, Egypt. Using a scanning electron microscope to investigate ancient desiccated grains, he found that the internal structure remained intact. Individual starch granules within the endosperm could be seen with little holes or pits, where the enzymes had begun to convert grain starch into sugars. There are lots of wonderful scanning electron microscope images in his paper.

Carbonised, or charred grain is found on many archaeological sites in Northern Europe and the British Isles. The matrix of charred or carbonised grain has been destroyed by heat of the fire, so it is not possible to look at individual starch granules. Although carbonised grain is often used just to provide a radiocarbon date for the site, there might be other clues for the archaeologist and archaeobotanist that reveal what kind of grain processing techniques were taking place. Such as separated embryos, fragmentation and friability.

what happens on the malting floor?
Barley, wheat, oats, sorghum and rye can all be malted. I hope these diagrams of grain and malt will help to explain how the grain germinates. This is how it works at a basic level.

slide10.gif (48960 bytes)
section through a barley grain, showing the component parts. source Danish Malting Grou
When the grain has been sufficiently steeped and aerated in water, growth hormones (gibberellin) are activated in the scutellum and embryo. These growth hormones stimulate the production of enzymes in the aleurone layer, which is a thin layer of special cells, just beneath the husk.

The maltster knows, through skill and experience, when the grain is sufficiently steeped. The wet grain is transferred to the malting floor, where it is piled up, then gradually raked out into a bed, a few inches deep. Here it begins to germinate. When rootlet and shoot are about one third the length of the grain, it is called green malt, and the next stage is to carefully dry it. 

slide11.gif (26941 bytes)
section through a malted grain, showing the chemical pathways. source Danish Malting Grou
Biochemical changes occur within the grain as it germinates on the floor. The enzymes that were activated within the aleurone layer begin to convert grain starch into sugars, the initial food source for the growing grain. These are the same enzymes that re activate in the mash tun and make a sweet mash. Other enzymes break down the husk, making the grain friable and, therefore, easier to crush than unmalted grain.

Malt, therefore, is made up of mostly starch, with a few sugars and, most importantly, those dormant starch converting enzymes that re activate in the mash tun at the right temperature.

Grain germination has a complex biochemistry. Scientists still don't fully understand how the aleurone layer works. If you want to know more detail, have a look here. If you want to read even more detail, have a look here, at chapter 14 of 'Barley: production, improvement and uses' by Steven Ullrich. Or get hold of a copy of Bewley and Black.

The products of brewing are ephemeral. Malt goes into the mash tun, wort is fermented into ale which people drink, spent grain is fed to animals and waste liquid is washed down the drains. For the maltster and the brewer, it is a tragedy if the grain barn is destroyed by fire while the malt is being dried. For the archaeologist and archaeobotanist, it is a wonderful thing because the grain is carbonised and it is therefore preserved for analysis.

drying the green malt
Straight off the malting floor, it is called green malt. The maltster stops the growing process by gently drying the malt in a kiln. Gentle heat does not destroy the enzymes. Warm air passes through the malt, usually over several days. Traditional grain drying kilns do not have a solid floor. The malt is put upon a permeable floor to dry, so that warm air passes through the grain bed. Making good malt is a skilful task.

Today, maltsters produce a variety of types of malt by kilning at different temperatures. Base malts are kilned at lower temperatures. The enzymes are not destroyed and will remain active in the mash tun. Specialty malts are kilned at higher temperatures, destroying the enzymes. These provide only colour and flavour to the beer, making up no more than 10% of the grain bill in the mash tun. Specialty malts have been developed over the last two hundred years, making a wide range of beers possible from pale ale to dark stout.

SEMs of carbonised grain from Balbridie 'timber hall', Fife, Scotland
I spent a few years making funding applications, hoping to continue my research into the archaeological evidence for malt and get a PhD for it. That never happened but, working with the Satake Centre for Grain Process Engineering at UMIST, Manchester, I was able to get some scanning electron images of ancient carbonised grain from a neolithic site in Scotland. These SEM images were taken to accompany our funding applications and they were not originally intended for publication, but I think enough time has passed for me to now put them up on my blog and share them.

I was given six tiny carbonised grains from the thousands that had littered the floor of a 6000 year old, early neolithic rectangular timber building in Scotland. The building was destroyed by fire. Professor Ian Ralston, one of the original excavators, was kind enough to send me them. Three of the grains had missing embryos, visible with the naked aye and very clear under a normal microscope. One of the grains was examined using a scanning electron microscope and it shows the missing embryo, on the right, indicating that it has begun to germinate.

More of the grains from the site would need to be examined, to identify how many had begun to germinate. If it turns out to be a high percentage, and if the grains are friable and poorly preserved, then this is a deliberate malting for the production of ale in neolithic Scotland. Several SEM images of the same grain were made. The image below shows that the endosperm of the grain has been badly damaged by the fire. But it is possible to just about see the aleurone layer, beneath the husk. 


Moving in closer to see the detail of the husk, we were very surprised indeed to see that the aleurone layer, that special layer of cells that kick starts the germination process, is visible, intact and well preserved. The husk has begun to be broken down by other enzymes, as can be seen in the bottom left of the image, and the grain was friable and fragile. All these are good indications of being malted.


This final image of that little carbonised grain show how well the individual cells of the aleurone layer have been preserved. They look rather like sponges, and some appear to have been activated. The more you look at this image, the more detail you can see. It is possible to make out erosion pits, beneath the individual aleurone layer cells, that indicate that the enzymes have begun to hydrolyse starch into sugars.

This is my favourite SEM image of an ancient grain. I think it would be a very good research project for someone to look at ancient carbonised grain from as many sites as possible. Changes in the aleurone layer cells and degradation of the husk might prove to be important criteria for the identification of malt. 

I would love to do this, if anyone wants to help out with funding and with samples of carbonised grain from archaeological excavations from any era. 

I would, of course, like to look at carbonised grain from neolithic sites in particular. 

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supplementary notes: 3rd March 2015 see here for the full details and the academic reference.

Some carbonised grains were found at Nevali Cori, a site not far from the Euphrates river. Here are some extracts from the botanical report, which describes a 'roasting pit area' and carbonised grain that appears to have missing embryos. Could this grain be malted? In an Iron Age context, it would probably be described as malt by archaeobotanists. 

When grain like this, damaged and with missing embryos, is found in a pre pottery neolithic or Bronze age context, an interpretation of "malt" is considered 'controversial and speculative. I wonder why. 

The drawings of grain and extracts below can be found towards the end of the document. I welcome comments and discussion about this, and the idea that missing embryos in carbonised grain indicates that it has been malted. 


Investigations of Botanical Remains from Nevali Çori PPNB, Turkey: A Short Interim Report 
R. Pasternak

The site:
Nevali Çori (NÇ) is located near the Turkish town of Urfa (37°60'N, 38°70'E, 490 m above sea level) on the slope of a Euphrates side valley. The 14C analyses, only available from the early levels, provided dates of ca. 8400 BC (calibrated). The settlement was occupied from the Early PPNB to the early Bronze Age (Hauptmann 1984, 1987, 1988, 1997). The PPNB layers included stone houses and a temple building of around 200 m2. On the slope in front of the houses a 'roasting-pit area' was found with a number of hearths in close proximity to each other. Most of these hearths were in use during the earliest phases.








Damaged grains from Nevali Cori

Sunday, 13 July 2014

where have all the malting floors gone?

There are only a handful of malting companies in the British Isles who still use the ancient and traditional technique of floor malting. One of these is Tucker's Maltings, in Newton Abbott, near Exeter, Devon. They are the only Maltings in the UK who offer regular guided tours. Another is the Warminster Malt Company, established in 1855. Guinness owned and operated this Maltings between 1950 and 1994. It provided the malt for the famous brew. When they moved out, the new company provided quality floor malt for several small independent craft breweries.

The Crisp Malting Group is a large company, with malting plants operating in Scotland and England. They own Maltings in Alloa and Portgordon, Scotland, and also in Ditchingham, Great Ryburgh and Mistley in Suffolk, Norfolk and Essex, respectively. The site at Great Ryburgh is the largest and, as they say on their web page, it provides an insight into the technical developments and innovations that have taken place in the malting industry over the last 150 years. The Ryburgh Maltings was set up in the 1850s. It eventually became the largest floor malting plant in Europe. They still have and use some of the traditional floor malting facilities. Today, however, because of demand, most of the malt is produced using modern equipment. These are the Saladin Maltings, installed in the early 1960s. Circular germinating vats, also known as drum maltings, were added in 1973. In the early 1990s, modern computerised systems were introduced.

These modern systems can deal with large amounts of grain but the fundamental processes of steeping, malting and kilning remain unchanged. If you want to see just how huge the modern computerised GKV systems can be, here is a time lapse video of one being built between August 2011 and February 2012 for the Great Western Malting Company. It will replace the drum maltings. In the 21st century, making the equipment for malting has become a big industry in itself. 

A working floor at Fawcetts Maltings
malt being turned by hand on the malting floor at Fawcett's, Castleford, Yorkshire
There is also Thomas Fawcett & Sons Ltd, based in Castleford, West Yorkshire, where the original malting floors are still in use, alongside the Saladin Maltings and a state of the art germinating kilning vessel. The family has been making malt since the 1760s. Established in 1809, the family business and company has seven generations of experience of making malt.

We contacted them not long after visiting the Corrigall Farm Museum on Orkney where we had seen the traditional 18th century grain barn, complete with threshing and malting floor. Fawcett's were kind enough to take us on a guided tour round the Maltings and explain what they did. That was in 1997, just before I completed my thesis. It gave us an insight into the complexities of malting on an industrial scale. A more recent description of a tour around Fawcett's is here. It seems that not a lot has changed there over the last 17 years.

So, where have all the malting floors gone?
Replaced by modern technology, almost every one ...

It's crucial to turn the malt regularly. This aerates it and prevents the rootlets from becoming entangled and matted on the malting floor. This important job has traditionally been done by people, who pulled a specially designed malt rake through the germinating grain. It is a time consuming process. As the malting floors became larger and larger to cope with the demand for beer and whiskey in the Victorian era, so the task of turning the malt became increasingly labour intensive and expensive.

In the 1890s, a new mechanised system was invented by Charles Saladin, a French engineer (1878-1942). Named after him, the Saladin box was a large concrete or metal box in which revolving metal forks moved slowly from end to end, turning and aerating the grain as it germinated. The picture below is from a Belgian malting company's web pages, Dingemans, who began to use the new mechanical system in the early 20th century. The malt needs to be aerated and, as time went by, the basic design has been improved with perforated floors, and air being blown through the germinating grain to maintain an even temperature. Drum maltings are essentially the same system, but with circular grain beds, not rectangular boxes.

a classic Saladin box malting (image from Dingemans Mouterij, Belgium)

In the British Isles, the malting floors began to be replaced by Saladin box maltings slightly later than in Europe, with the first being installed in Edinburgh's North British Grain Distillery in 1948. They became increasingly popular during the 1950s and 1960s. Saladin boxes and pneumatic maltings, where the germinating grain is aerated, have been improved upon by larger capacity drum maltings and more recently by enormous computer controlled state of the art Germinating Kilning Vessels.

Malting equipment in the modern food processing industry has become huge and complex, yet it is still based upon the fundamental processes of steeping, germination and kilning. There is a very good analysis of modern malting techniques and equipment here, Chapter 3 of ' Engineering Aspects of Cereal and Cereal Based Products' edited by Raquel de Pinho Ferreira Guine, Paula Maria dos Reis Correia.

malthouses
Apart from the Nottingham cave maltings, dated to the 13th and 14th centuries, there are very few recorded malthouses or facilities for making the malt in the medieval era. Mostly, malt was made in the grain barn. The cave maltings are unique. Because of the ambient temperature being the same all year round, they could make malt all the time. In a traditional grain barn or malthouse, it was only made in the cooler months of the year, those months with an 'r' in, that is, any month except May, June, July and August when it was too hot to make malt. Over the centuries, as the breweries gradually became larger and more centralised in towns, so the malthouses and malting floors had to become much larger to supply them.

Great Dunmow Maltings
Great Dunmow Maltings, now a museum
The details of the commercialisation, industrialisation and mechanisation of the malting process in England is very well told by Amber Patrick in her report for English Heritage. She explains that the basic 16th century malthouse had two floors, the top being for grain storage and the ground floor was the growing floor. The kiln for drying the malt would be at one end. A good example is the Boyes Croft, Great Dunmow, Essex, a Grade II listed building.

By the end of the 17th century, commercial malting was on such a scale that it warranted taxation. The Malt Tax was introduced in 1697 and was not repealed until 1880. The malting industry became highly regulated and the buildings became larger, sometimes with two malting floors, one above the other. Amber Patrick explains that the trend for the last three or four hundred years has been for the malthouses to become bigger and bigger.

The Industrial Revolution and the construction of the canals, then the railways, greatly accelerated this trend. It became easier to transport large quantities of malt to the breweries quickly and efficiently. More multi storey Maltings were constructed in the 18th and 19th centuries, usually right by the canal or the railway.

Bass Maltings, Sleaford, with its' own railway line. Currently up for development for housing

an aerial view of the Bass Maltings - the largest floor maltings in Britain.

The Bass Maltings were built between 1903 and 1906. There was an engine house, to provide the power for shifting around the huge amounts of malt that was made there. It was originally planned to build eight more malting buildings, mirroring the eight that did get constructed. It was a state of the art, hugely mechanised turn of the century floor Maltings, one of the last to be built in Britain. It closed down in the 1960s, with the introduction of box and pneumatic maltings, which could produce more malt at a cheaper cost.

While browsing about on the internet, I found some fascinating images of the inside of the Maltings, on a blog about decaying industrial buildings, www.adarkertrantor.co.uk. They were taken in 2012 and they show how this important industrial site was abandoned with much of the equipment still there.


Malthouses were huge, multi storeyed and functional, yet they could still be attractive buildings. As I was writing this blog, I looked on the internet for a suitable image of a disused Maltings that I could use. The difficulty in finding an image online of an industrial malthouse is that most of them have been closed down or demolished in the last few decades. Many have been converted into flats and housing developments. Some have become offices and others are Listed Buildings. I came across this recent story from the Newark Advertiser, about a Grecian style Maltings that is up for sale and future development. It is a good story, well worth reading, since it tells you who owned it and how it came to be built. The Maltings was built in 1864 and it was last used to make malt in 1966. It could be the story of any industrial maltings.

the Maltings at Newark is up for sale as I write this, details here

Making malt in the the ancient and traditional way is being revived in the USA. That's great news - I know about a few people who are doing this. If you are making malt on a small scale, using traditional techniques and I have missed you out, please let me know.

 Valley Malt, Hadley, Massachusetts

 Riverbend Malthouse, North Carolina

Rebel Malting Company - they use a Saladin system

Colorado Malting Company

further reading

Amber Patrick Maltings in England a report for English Heritage, 2004

Christine Clarke, The British Malting Industry since 1830 published in 1998
Summary: "Malt is the main ingredient in the national beverage, beer. For centuries the malting industry has provided a principal bridge between agriculture and the brewing industry, yet its history has been little studied. The British Malting Industry since 1830 is the first overall account of malting, dealing with the processes, products and sales, owners and employees, and with the evolution of what in 1830 were almost all small, local businesses. Christine Clark traces the influence of the growing demand for beer in Victorian England, and of the increasing power of the large breweries, on the malt industry ..."

Roger PutmanBeers and Breweries of Britain (pages 9-12),published 2004




Thursday, 26 June 2014

traditional floor malting & neolithic grain barns


The first malting floor that I saw was about 200 years old and made of local clay. It was at the Corrigal Farm Museum on Orkney, a late 19th Century farm with stables, two fine stone built barns, one for the animals and the other for processing and storing the grain. It has a threshing and malting floor, good dry storage and a grain dryer. We had visited Orkney in the summer of 1996 to see Skara Brae, the stone circles and other neolithic sites. The visit to the farm museum was a significant day in our understanding of traditional grain processing techniques - threshing, winnowing and making the malt. The curator at the time was Harry Flett, a man with plenty of experience of farming, malting and brewing. He talked to us about the traditional way that grain, usually bere barley, was turned into malt and how the grain barn worked. It gave us an insight into how the "first farmers" of the Neolithic would have processed the grain they grew - it is not just about grinding the grain into flour for bread or making some kind of gruel or porridge. Grain can also be malted.
Product Image
Corrigall Farm, Orkney - the grain barn, with drying kiln
Malt is the main ingredient for ale and beer. It is the source of sugars for fermentation. The brewer takes the malt, crushes it lightly, mixes it with hot water in the mash tun to make a sweet liquid, the wort. After the wort is boiled with herbs or hops, it can be fermented by the addition of some barm, the yeasty froth from the previous brew.

Harry Flett said he would make some bere malt in the barn for us, so that we could brew a traditional Orkney beer. He was as good as his word. Some time later, back in Manchester, we received an 18 kg sack of malt from him, in the post. This was the last batch of malt to be made in the Corrigall barn.

Graham used it to make an ale, adding a few ounces of dried meadowsweet flowers instead of hops. There was three times more draff or spent grain than you get from modern barley, but only half the potential sugars. This is because bere is an older strain of barley, much skinnier than the barley that is grown today.

threshing & winnowing
The earth and clay floor of the grain barn is ideal for threshing. A stone floor would break the flail and damage the grain. Working the flails requires skill, team work and care. The barn has two opposing doorways, so that you can winnow indoors in bad weather. Winnowing separates the grain from the chaff. The principle is simple. You throw the grain up into the air on a windy day. The grain falls to the ground. The fine chaff blows away.

Today, the whole job of threshing and winnowing is done by combine harvester, so a grain barn is not needed any more.

All a grain barn needs: opposite doorways for winnowing, a clay floor for threshing and malting, a malt shovel and a grain drying kiln. It is not possible to dry grain or malt on the floor of the barn.
The grain and malt bruiser is on the right of the kiln entrance.

making the malt
Harry told us that, traditionally, a sack of bere barley was left in a shallow stream for a few days. There is a convenient stream just behind the Corrigall Farm. Steeping is a specific process, as the grain awakens from dormancy it needs oxygen as well as fresh water. A shallow, fast flowing, tumbling brook is perfect.

The clay floor is used for malting. When the grain has been steeped for 3 or 4 days, it is then heaped onto the floor, where it can drain a little. It is then gradually spread out, as it warms up, into a layer a few inches deep as germination progresses. Making the malt requires skill, knowledge, time and patience. There are a few historical accounts of how the malt was traditionally made. John Firth, in his book Reminiscences of an Orkney Parish (1920), writes that every farmer was his own maltster. The bere would lay on the floor for several days, by which time it had begun to germinate, or "show twa taes". This refers to the rootlet and shoot. Next the grain was rubbed or trampled to remove them and to prevent further growth. It was then piled into a 'sweet heap', covered with sacks and straw insulation and left for a few days. This seems to be a particularly Orcadian tradition of making the malt, and the effect is that the heap heats up and the enzymes in the green malt begin to digest the starches. This makes a very characteristic aroma, and a sweet liquor begins to ooze from the heap. What green malt is not used immediately is dried gently in the kiln so that it can be stored for future use.

Traditional malting, then, involves mimicking the natural conditions in which grains grow. This is done by laying the steeped grain on a smooth, well maintained floor surface in a dark, well ventilated building, such as a barn, until the process of germination is visible. Then it is called 'malt' and it is dried, slowly and gently, in a grain drying kiln.

The kiln fire is not situated directly beneath the malt, rather it is set to one side. There is a flue which takes the warm air to the bowl shaped base of the kiln, and which will hopefully lose any sparks on the way. The bowl has a ledge, and a lattice of sticks is spread over this ledge and a central shaft, called a kiln lace. Straw is spread over this, and the damp green malt spread over that. It takes a long time for the malt to dry, and the fire must be tended with care. Towards the end, when the malt is dry the underlying wood and straw is very dry, and prone to ignition. If this occurs the kiln lace is withdrawn and the assembly falls to the bottom of the bowl, and hopefully extinguishes.

Many malt barns have been known to burn down.

left to right: the fire hole, the drying kiln, a mash paddle and malt shovel and the malt, grain or oats mill, used to bruise or lightly crush the malt.
The grain drying kiln at Corrigall is the best preserved on Orkney, but there are lots of other traditional grain barns that are still standing. The Scapa Flow Landscape Project has recorded some of them, and you can read more details of how to dry the malt, the oats and the grain here. 


Scientists have only recently begun to understand the biochemistry of malting. Maltsters have known the techniques for thousands of years. Once known as the 'ubiquitous craft', there were maltsters in every town and village, large households and farms. Most farmers knew how to make their own malt. With the advent of the Industrial Revolution and the improved transport and communications, malting became more centralised and larger. For example, Thomas Fawcett & Sons Ltd of Chesterfield is built on the banks of the canal, and the later railway passes close by. Eventually small scale malting ceased except in the more remote rural communities like Orkney.

Below, a photo of the Kirbuster Farm Museum, with buildings ranging from early Medieval to Victorian. The grain barn has lost its' roof, but the grain drying kiln is mostly intact. The nearby clear, bubbling stream is not seen on this photograph.
Kirbuster Farm grain drying kiln see here

We can summarise the necessary features that a Grain Barn requires:-

... it must be close to a reliable source of fresh, running water
... a dark, well ventilated building
... a smooth, regularly repaired, well maintained floor made of beaten earth or clay 
... a way of drying the malt by gentle heating
... dry storage facilities
... people who have necessary skill and knowledge - a maltster

neolithic grain barns, malting floors and kiln fires
The "first farmers" of the British Isles began to grow and process grain about 6000 years ago. They lived in circular houses, such as the ones that have just been built at the new Stonehenge Visitor Centre. They also built structures that archaeologists call 'rectangular timber buildings'. These vary in size, from the huge hall at Balbridie, Fife, Scotland, to much smaller structures, such as the one dated to the early neolithic which was recently discovered at the Braes of Ha'Breck, on the island of Wyre, Orkney.

These two buildings were clearly involved in grain processing and storage. Thousands of carbonised grains of wheat and barley were found at both sites. Balbridie was completely destroyed by fire and Wyre was partly damaged. The timber building at Wyre appears to have been re floored, re built and used again after the fire. Current archaeological theory suggests that these buildings were deliberately burned down, perhaps as a kind of special memorial event for the community. It has even been interpreted as a 'ritual event', one that would have been spectacular and visible for miles around.

Most of the early neolithic rectangular timber buildings in Ireland were destroyed by fire. Between fifty and sixty rectangular timber structures have been identified so far in Ireland. Carbonised grain, spikelets, glumes and other indications of grain processing activity have been found in many of these excavations.

I suggest that it is far more likely that these buildings were destroyed or damaged by an accidental kiln fire, caused by the drying of the grain or the malt when it went very badly wrong. Fires at Maltings have been a common event throughout the years, even in the 20th century. The photo below was taken in the 1990s and shows the kiln fire at the Maltings in Newark.

kiln fire, Newark Maltings, 1990s, photograph thanks to Ivor Murrell, retired maltster.
There are so many rectangular timber buildings of Neolithic date that have burned down that it is not practical to name them all. In future posts, I shall be looking in more detail at the excavations of some of the more interesting ones. Sadly, as a rule, floor surfaces rarely remain in good condition in the archaeological record.

Lough Gur, Building A
There is one notable exception. At Lough Gur, a neolithic and bronze age site in Ireland, a timber building, rectangular in shape with a well preserved beaten earth floor was excavated in the late 1940s. The Lough Gur excavations were published in the Proceedings of the Royal Irish Academy, Volume LIV, Section C, Number 2, 1951. I had to get special permission to access this volume from the stacks at John Rylands University Library, in the final months before the submission date for my Master's Thesis. It was well worth it. This building is a very good candidate for a grain barn, with facilities for winnowing, a threshing area, a malting floor and evidence of a hearth, or grain drying area. The image below is from one of my, as yet, unpublished papers.


Horton
Recent excavations at Kingsmead Quarry, Horton, Berkshire, England, have revealed the archaeological evidence of four Neolithic buildings as well as a rich female beaker burial, dated to the Bronze Age, which I discussed in an earlier post. Two of the buildings were rectangular and carbonised grain was found at one of them. This shows that grain was either being stored or processed there in the early neolithic, around 6000 years ago. There is an unusual feature that seems to be associated with this particular "neolithic house".

a neolithic building was excavated at Horton - what is that pile of fire reddened stones on the left?
We were curious about this pile of reddened stones in the corner, behind the house. We could find no mention of them in the online reports. They look rather like bricks, but appear to be a part of the neolithic feature, contemporary with the "house". We find this feature very puzzling. Graham managed to make a larger image of these stones.

is this the remains of a trough, with fire cracked stones?
Given the early neolithic date of some recently discovered burnt mound troughs, with fire cracked stones, in Northumberland, England, at a site called Bradford Kaims, it must be considered a possibility that this little rectangular timber building had a trough at the back of it. Not every neolithic building was a house. Some of them were used as barns - something that would have been very useful for those 'first farmers' of Neolithic Britain.

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further reading
The Craft of the Maltster
a paper that should be published very soon, the result of my presentation at the Food in Archaeology Conference, Exeter University, April 2010.

John Firth, Reminiscences of an Orkney Parish
originally published in the 1920s, re published in 1974

and finally,


here is a page from Firth, with a ground plan of traditional Orkney farm buildings, showing the grain drying kiln, flue and more.

... breaking news!
6000 year old "house" discovered in Yorkshire, England
http://www.cravenherald.co.uk/news/localnews/11301773.Archaeology_students_find_6_000_year_old_house_remains_at_Yarnbury_Henge__Grassington/












Wednesday, 18 June 2014

The origins of the Viking bathhouse myth

We have spent some 10 years arguing that that the "first farmers", the Neolithic culture that brought cows, crops and ceramics to Britain 6000 years ago, possessed the material culture necessary for turning cereals into ale, and that there is sufficient archaeological evidence to merit investigation. Nobody in the archaeological community could be convinced. It is still considered to be a controversial theory. We have no idea why. Maybe it is a paradigm shift too far for some archaeologists to bridge, that cereals were initially cultivated for their potential sugars, a status crop, and not for their starches, a staple crop. So we considered investigating an era in which there should be no controversy.

We visited the island of Wyre in Orkney, and inspected "Cubbie Roo's" castle. This was built by Kolbein Hrugr, hrugr means "heap", he was a big man. It is mid 13th Century and one of the older mortar and stone built castles extant in Scotland. It is a fascinating site on one of the now remoter islands of Orkney. We were surprised, amazed and overwhelmed to find a stone built "mash oven" in an outbuilding round the back. Our excitement was because this could be the oldest mash oven in Europe. This building has a stone bench, perfect as an ale store, and drains. It would be very suitable for making ale, but so far archaeologists have interpreted this as just an ordinary oven.

Cubbie Roo's mash oven, Wyre, Orkney.


the medieval brewer, stirring the mash

We are lucky on Orkney to have well preserved Viking sites. A friend and neighbour suggested that we might like to look at the drains at the site on the Brough of Birsay.

Birsay is the late 10th Century base of Sigurd the Stout and his son Thorfinn.  In the Orkneyinga Saga they are renowned for their hospitality. We can imagine the great feasts they had there. This might even be the site of Sigurd's Yule Feast, where Kari slew Gunnar Lambi's son in front of King Sigtrygg of Dublin ( pp xxvii-xxviii, Orkneyinga Saga, edited by Joseph Anderson.)

Drains are significant for brewing installations. The mashing process makes sugars from the malt and these are very sticky and messy. Any spillage or accidents have to be washed away, and the brewing equipment has to be kept clean. A brewery cannot function without effective drains.

one of the massive stone lined drains at Birsay

There is a massive drain running down the middle of what I think is the head of the Viking causeway, most of which has been eroded by the sea. To the right of this causeway, looking back to the mainland, is the so called "Viking Sauna" (see photo below) with stone slabs on edge, supposedly to support wooden benching. I heard an expert on TV saying that "they poured hot water down the drain under these benches, to keep their bums warm". I think it's far more likely to be the brew house and ale store.

not the sauna - this is the brew house and ale store
On the left of the causeway, looking towards the mainland, is a building interpreted as a "Bathhouse or Sauna", in the photo below. It looks more to me like a mash house. It has a bench and a large hearth and drains along the wall. One end has been lost to the sea, and it is thought that there was a large hall or langskaill further out to sea.

the mash house, with large stone shelf & several drains

I was puzzled. These installations are little different to the Orkney Brewery, which is just down the road at Quoyloo. Rob Hill's Swannay Brewery, also on Orkney, uses the same installations - a mash tun and fermenting vessels. How on earth could anyone think that these buildings were a Bathhouse and a Sauna? Maybe they knew absolutely nothing about how beer is made.

When I get puzzled by archaeology, I like to read the original excavation reports. This tells me what came out of the ground and there are usually nuggets of really useful information that are lost or not mentioned in summaries.

The earliest reference to 'Viking Bathhouses or Saunas' that I could find came from Dr Alexander Curle's excavations at Jarlshoff, Shetland, published in 1935, in the Proceedings of the Society of Antiquaries of Scotland (PSAS 69). He wrote that "...the presence of such a drain, and the condition of the ash deposited within it, suggest the possibility of the remains of a bath-house existing nearby." (page 284).

Curle explains that this is the first Viking settlement excavation in Britain, and that his interpretations are based upon the work of Thorsteinn Erlingsson, who wrote about Icelandic settlements. In his book  Ruins of the Saga Time, published in 1895. Erlingsson describes the components of the traditional farmstead house, including the bath-stofa or bathroom. He describes it as being part of the main structure and it is not a separate building.

Jarlshof, Shetland - is this the bath house, hof, a religious building or a brewhouse?

The structure in question at Jarlshof (see photo above) was beneath a mausoleum and it was not excavated until the 1950s by JRC Hamilton. Alexander Curle did not actually excavate it. In the foreground is a large longhearth and a substantial drain. To the rear of the building there is what looks to me like the bowl or footings of a grain drier.

So how on earth could Dr. Curle know that it was a bath-house, other than making the assumption that it was, because of the drains and and a means of heating water?

This remained a mystery to me until I stumbled across Dr. Alexander Curle's excavation report for another Viking age site, at Freswick, Caithness, Scotland, published in the Proceedings of the Society of Antiquaries in 1939, see PSAS 73 . In this, he describes a feature that, at first sight looks very much like a small Roman style bath-tub, with a large hearth and drains.

I was devastated, despite the complete absence of any mention of bath-houses in the Sagas, here was an archetypal bath-house. The Sagas describe the practice of bathing in streams, lakes and rivers. There were even open-air hot baths in Iceland, thanks to the natural hot springs there. Otherwise the Vikings habitually bathed in tubs of hot water in the andyri or porch. Even the King of Norway took his bath in a tub. 

reconstruction of Snorri Sturlussun's 'bath house' makes use of a hot spring, 
it is in the open air and is nothing like the buildings at the Brough of
Birsay & Jarlshof.

Then one day I re-read "The Vikings in Scotland" by James Graham-Campbell and Colleen E Batey. On page 198, the Viking settlement at Freswick is discussed:

"... as part of the re-examination of this building through  the surviving records, several problems became clear, the most significant being the complete stratigraphical separation between the secondary structure and the underlying drain. These could never have been associated and thus the secondary building is unlikely to have been a bath-house."

It was now obvious to me. Dr Alexander Curle was already aware of Freswick when he excavated Jarlshof, and this had influenced his interpretation. It has also influenced the interpretations of Viking sites for many other excavators and archaeologists since then. Whenever they find drains and a means of heating water, they interpret it as a "bath-house", even though the original archetype has been found to be wrong.

Interestingly the Brough of Birsay was excavated under the direction of Dr Curle's daughter-in-law, Cecile Curle, so she would have followed the family tradition and their interpretations. 

In short, most archaeologists do not know how to make beer from the grain. They certainly drink it, and they may even have made beer from kits, but they do not understand the processes, and so they do not recognise the installations in any era up until the late Mediaeval when monasteries brewed.

What a sad loss.
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further reading
We presented a poster at the 7th Experimental Archaeology Conference, Cardiff University. It can be downloaded here:

Where were the Viking Brew Houses? 


more reading (added June 25th 2014) 
We wrote a paper for the EXARC Journal, it has been peer reviewed and it is currently on the member's only section of the Journal. It will be released for everyone to access, download and read in the near future, probably later this year.

In the meantime, here is a shorter version of that paper, published in the Orkney Archaeological Society Newsletter. We called it 'Where did the Vikings make their ale?'.

Update

Lars Marius Garshol has been studying Norwegian Farmhouse brewing for a long time and is an expert in this field. The methods and equipment that he describes seem to us to have changed very little, if at all, from those of the 10C.
For anyone who wishes to understand or recreate Viking style brewing his work is an invaluable resource. Here is his Blog.

Lars' Blog