Friday 30 December 2016

alcohol production

There is a debate in the academic literature of archaeology and anthropology about alcohol production, the archaeology of alcohol and the consumption of alcoholic beverages in the past. It seems to be an increasingly popular area of study. Search the internet using these phrases and you will find plenty of books, papers and articles. Unless you have access to a University library, however, many of them are not easily accessible. They are behind pay walls.

The phrase 'alcohol production' neatly avoids the science, biochemistry and technology behind a number of varied and differing processes for making alcoholic drinks.

This generalised idea of 'alcohol production' is about as sensible and informative to understanding the processes as talking about 'metal production'. Different kinds of metal obviously require specific methods of production. Copper, bronze and iron are produced in very different ways. It's the same with making different kinds of alcohol from different sources of sugars.

No-one would ever believe that a primitive kind of weak metal could be produced by accidentally leaving some coloured rocks in a fire overnight. However, the story goes that a primitive sort of beer was discovered when a container of grain was left outside, it rained, the grain got wet, it germinated then it fermented and made some sort of weak beer. Or, maybe, a loaf of bread fell into a bucket of water, then it fermented. This simply cannot happen, it would defy all the laws of biochemistry.

One aspect of this 'alcohol production' debate is that grain can somehow naturally ferment into a weak beer when immersed in water. We have been told by a number of archaeologists that to make a primitive beer you don't even need malt and that barley can naturally ferment. This is scientifically and technically impossible. The idea of natural fermentation was first presented in this paper dating from 1991 and many subsequent academic papers cite this as evidence.

It is one of the myriad of anecdotal myths about alcohol, for example that animals can get drunk by eating rotten fruit. We shall write more about this sort of thing in future posts.

Grain is a living thing. When left in a bucket of water the grain drowns, it goes bad. Grain requires both water and oxygen to begin germination. For details of steeping the grain in a bubbling stream see an earlier post about how to make a base malt.

The idea that early beers or ales were somehow weak and inferior is also fallacious. If it were weak it would then be useless for that 'altered state of consciousness' that was, according to the academic literature, necessary for social feasting or ceremonial occasions. In Britain any alcoholic drink of less that 1.2% is not considered to be intoxicating, and is not subject to any Excise tax laws or regulations. Beer of less that 2.8% alcohol is classed as 'small beer", and is subjected to a low tax, whilst beers above 7.5% have a higher tax. Beer can be made to any strength the brewer wants.

Alcohol is produced by yeast when it digests sugars in the absence of oxygen. In the presence of oxygen, however, the yeast will produce water and carbon dioxide but no alcohol. You need anaerobic conditions for alcoholic fermentation. Yeast cannot ferment starches, only sugars. Sugar ferments into alcohol. Cereals do not contain any sugars. Therefore, it is absolutely impossible to make alcohol from grain by natural fermentation.

The concept of 'alcohol production' should be replaced by 'sugars production'. This would be a revolutionary paradigm shift in archaeological theory. Cereals can be easily converted into sugars when you have the right knowledge and skills.

Cereals are not just a staple crop, they can also be considered a status crop.

Grain can be converted into sugars by first malting it. Malt is partially germinated grain, it has the necessary enzymes, alpha and beta amylase, to convert starches into sugars in the presence of water. This occurs most rapidly when hot, at around 65 degrees Centigrade. The water is not only a suitable medium but it's also a necessary part of the biochemical reaction, hydrolysis. This is the mashing or saccharification process.

What, exactly, is malt? There is very little discussion of malt and malting technologies in the archaeological and anthropological literature. What is written appears to derive entirely from scholarly works written by archaeologists and anthropologists. There is no input from maltsters or brewers who actually work with malt. The archaeological and anthropological literature is self referential and frequently wrong. For example, malt is sometimes described as 'toasted, roasted, sprouted grain' which is not an accurate description of a base malt that provides the fermentable sugars in the mash tun.

When you roast the malt at hight temperatures then you destroy the enzymes and there will be no sugars to ferment into beer. Roasted malts are a modern phenomenon, dating from the around the 16th and 17th Centuries AD. There is an incorrect description of making malt for brewing by roasting it in a kiln in this paper.

Malting and the production of of liquid malt sugars is probably one of the first, if not the first, cereal processing technology. It's far easier to wet process the primitive grains that have more husk than starchy endosperm into desirable malt sugars than it is to grind them into good flour to make bread. To make porridge or gruel, the grains must be boiled for hours.

Malting and the production of liquid malt sugars from the grain was widespread throughout the Fertile Crescent, the cradle of agriculture, long before the rise of Islam. There is good evidence for deliberately made malting floors of stamped earth, clay and even of lime plaster at some of the first agricultural settlements of the Ancient Near East, for example at Beidha. Today the production and consumption of alcohol is forbidden by Islamic law. The civilisations of Ancient Egypt and Mesopotamia are well known for their beer manufacture. Now people no longer make malt in these countries.

There is a Biblical expression that describes "... a land flowing with milk and honey". Nobody thinks that this phrase refers to milk actually flowing through the fields. It is more likely to be a reference to rich grazing land that feeds the cattle, goats and sheep. The reference to honey seems to confuse the scholars. The Hebrew word debash or d'vash that is used in the Bible does not mean 'bee's honey' but, rather, it refers to an artificial sweetness of a vegetable nature, which scholars interpret as being made from dates, figs or possibly even grapes. To a brewer this is obviously wort, the liquid malt sugars. So the phrase 'land flowing with milk and honey' is a metaphor for rich pasture and arable land.

It's obvious that none of these scholars or archaeological experts have ever tasted sweet wort, straight from the mash tun. When we do mashing demonstrations we have invited people to taste the wort. Archaeologists have been known to refuse, sometimes backing away from us as if wort is somehow poisonous or horrid. No thanks, it's ok, they say. Those who do taste it usually say that it is sweet and delicious, commenting that it tastes like that stuff you get in jars for the vitamins. What they mean is, it tastes like malt extract, which is just concentrated wort.

Archaeologists Declan Moore and Billy Quinn came to Orkney ten years ago to have a look at our mash tun and brewing facilities. They both tasted the wort and were surprised, declaring it to be sweet and tasty. They were inspired enough to go and make some beer for themselves, in a spectacular way. They used a wooden trough and some hot rocks to re create a Bronze Age beer.

When brewers looks at a field of barley they see the potential for making malt for barrels of ale, beer or whiskey. Other people might see a field of grain to be used for making flour, loaves of bread, porridge or gruel. 

There are many malts and they can be rather confusing. There's brown malt, pale malt, barley malt, wheat malt, oat malt, millet malt, crystal malt, roasted malt, chocolate malt, amber malt, single malt, three year old malt and thirty year old malt. It's a huge list.

The last three are whiskeys made from barley that has been malted then mashed, with the wash from the mash tun (brewers call it wort) fermented and distilled. They have nothing to do with the case other than malt being the source of the sugars for fermentation. The first six are diastatic base malts, with enzymes, and with the power to convert starch into sugars. The four middle ones are modern specialty malts with no active enzymes. They have been roasted at high temperatures and this destroys the enzymes. These malts are decorative, used strictly for the colouring and flavouring of ale and beer.

The enzymatic power of malt is measured by obscure units, the Diastatic Conversion Coefficient. Modern barley malts can have a DCC of about 200 degrees, some might even have as much as 230 degrees. Around 37-40 degrees of DCC is considered sufficient for self conversion. That's to say, a grain only needs this amount of enzymes to convert all of its' starches into sugars. Early malts need not have had all their grains successfully or completely malted to effect a good conversion into sugars.

In the 1970s some archaeologists at the Butser Farm made some malt using their recreated 'heated malting floor'. They achieved only two degrees of DCC. Although they were pleased with their amber malt, what they had made was a specialty malt, not a base malt. It was not useful for providing the sugars to ferment into alcohol.

This excess DCC power of modern malts can be used in the production of sugars. One traditional recipe for potato vodka or potcheen is one part crushed pale malt, by weight, to five parts boiled potatoes. The excess enzymes convert the potato starch into fermentable sugars. 

It seems clear to us that, given the confusion and misunderstanding in the archaeological and anthropological literature about malt, what it is and how it is made and used, it's time that archaeologists and anthropologists started talking to the practitioners of the crafts of making malt and brewing beer.

The photograph below shows one of our demonstrations of the mashing or saccharification process. It was taken at the Eindhoven Open Air Museum a few years ago. We took some crushed malted barley, heated it in with water over the warm ashes of a fire made from wood and charcoal. Within one hour, the enzymes in the malt had converted all the starch into sugars.

This saccharification process works in a bowl and it also works on a hot flat stone beside the fire, provided that you keep the malted barley biscuit/cake wet all the time. You don't even need a container to mash.

The sweet bappir or 'cakes' on the stone were eaten very quickly, taken by visitors. In prehistoric times, the manufacture of malt sugars from the grain, by malting and mashing, would have been equally as desirable.

a demonstration of the mashing or saccharification process, using basic equipment 

We welcome comments and discussion, in fact, we look forward to them.

Wednesday 12 October 2016

a morning with maltsters, part four

Making Malt: in the final presentation we were taken from ancient times and traditional floor malting into the present day, where modern germinating kilning vessels can make up to 500 tons of malt at a time, in a continuous batching process.

Most of the malt made in Britain is used in the brewing and distilling industries, with roughly 500,000 tons of malt each year being used by commercial brewers and 800,000 tons going to the distilleries. There are around twenty million casks of whisky maturing in the 115 distilleries around the UK. Our third speaker, Eric Walker, was a man with lots of experience in every aspect of the malting, brewing and distilling industries. He began with a quick look at making malt in the distant past, pointing out that malt has been important for a very long time.

Its' origins are lost in the mists of time.

There's a story that ancient Egyptians, around 3000 years ago, may have made their malt by putting grain into baskets, then lowering the basket into a deep well. The basket could be raised and lowered, effectively steeping the grain. It would germinate in the basket and was shaken at regular intervals to prevent the rootlets from matting. Green malt was dried in the sun. The method is described in detail here on the Briess Malt web page. I'm not so sure this was an efficient way to make large amounts of malt for brewing. Perhaps enough could be made for small scale brewing.

It would be interesting to do some experimental and practical work, to assess the validity of the idea that malt can be made in a well, using a basket. I wondered how much malt could have been made in this way. There would not be enough to supply large vats like those at Hierakonopolis, a predynastic site in Egypt, which were probably used as mash tuns.

Beer was being made here in industrial quantities.

The vats, probably mash tuns, at Hierakonopolis, Egypt. Source here
The Egyptians must have used floors for germinating the barley. A malting floor is not an obvious thing to identify in the archaeological record. All that's required is a smooth level floor surface within a building. It's something that has been overlooked in the interpretation of archaeological sites. Archaeologists don't often interpret the remains of a building as having possibly been a grain barn or a floor surface as having been being suitable for making malt.

Eric talked about malting floors and the potential evidence for the manufacture of ale in prehistory. I was rather pleased that, on his next slide, he showed some of the evidence for the making of malt and ale in Neolithic Britain. That's my research.

There is good evidence for the manufacture of malt and ale at some of the Orcadian neolithic sites, such as Skara Brae and Barnhouse, six thousand years ago. At Skara Brae there were sherds from a large 30 gallon pot found beside the central hearth. Excavated by Vere Gordon Childe in the 1930s, no residue analysis was done on these pot sherds. Its' location would be an ideal spot for a fermenting barley wort. At the site of Barnhouse, another neolithic village, there was a possible malting floor as well as many drains which are essential for a brewer. Analysis of pot sherds using the technique of Gas Chromatography/Mass Spectrometry revealed "unidentified sugars and barley lipids" in the fabric of the pottery. It's a possible indication of sparging. If they were sparging to obtain a wort then they must have been making malt and ale. 

If you want to read more about neolithic and bronze age evidence, I suggest you have a look here at an article we wrote for Orkneyjar a few years ago. It's about the prehistoric transformation of grain into ale. You'll also find links to my published academic papers and to my thesis. I know of no other archaeologists who are working on the archaeological evidence for the manufacture of barley malt and ale in the neolithic. It seems to be considered a controversial topic by some academics, or so I am told. That's why I was pleased to see my work referred to at this malting seminar. Clearly the professional maltsters, brewers and distillers have no problem with the idea.

Eric described how floor malting is labour intensive, requiring skilled and dedicated people. It was the only way of making malt until the mid 19th century. The malt must be turned and raked on the floor, as well as being moved around the maltings from steep tank to germination floor, and from there to the kiln floor. It takes many workers to make the malt.

Modern pneumatic maltings changed all of this.

Two Belgian malting engineers, Galland and Saladin, are considered to be the fathers of modern pneumatic malting. In 1873 Galland designed a system of aerated rectangular boxes. A few years later, in 1880, Saladin introduced a mechanised turning system. The new integrated system of aeration and mechanical turning of the malt by Archimedes screws was called
a saladin box.

A few Saladin boxes are in use today, this one is at Tamdu Distillery
, source here

The workers who turned the malt cannot have been happy about this. For many, it meant the loss of their job. It was, in so many ways, a revolution in the malting industry, although it took several decades, until the 1960s, before Saladin boxes became commonplace in a maltings.

The technology of making malt developed rapidly. By the early 1970s, Saladin drums were being made and used. These are far larger and capable of producing thirty to fifty tonnes of malt at a time, in a continuous batching process. They can be operated all year round, in contrast to a traditional floor maltings that were subject to weather and temperature (see previous post). Much less manpower is needed, there is a lower cost of production. They consistently produce good quality malt in the quantity that is required today in the modern brewing and distilling business.

Germinating Kilning Vessel at Crisp's Maltings, source here

Germinating Kilning Vessels, can make up to 500 tons of malt at a time. I've not yet seen a large industrial maltings and have never looked inside one of these Germinating Kilning Vessels, but here's a man who has. Jeff Evans, on his blog inside beer, describes the experience:

"I climbed the stairs of one of these enormous, modern cylindrical towers to discover vast stainless-steel steeping tanks, malting floors and kilns. Having seen the simple, homely methods of the floor maltings, the scale and functionality came as a shock. Each of the tanks handles more than ten times the amount the entire floor malting facility can process in one go. 

At the push of a few buttons, the process gets underway – steeping, germination, kilning. Such are the efficiencies that germination is a day shorter here, and kilning only takes two days. The equipment is also much easier to clean, so you can see why new technology has its supporters in the industry. 

Once malted, the grains are quickly shipped out to breweries or malt merchants. Crisp’s job is done. The brewer will ultimately claim the credit for his wonderful beer, but, as the old saying puts it, you can’t make a silk purse out of a sow’s ear. There’s a lot of skill and care that goes into that drink even before the brewer starts his work. 

The next time you are entranced by a hoppy aroma as you raise a pint to your lips, stop, wait and think. Look beyond the green, tangy, zesty glory boys that steal the limelight and remember the malt and the maltster, the forgotten heroes of brewing."

In his final remarks about malt and malting techniques, Eric Walker reminded us of some of the fundamental principles.

Malt is a living thing. If it is not correctly steeped it can either drown or asphyxiate. It needs careful handling. The maltsters who make malt in these large vessels take as much care of it as the traditional floor maltster, there's a whole new set of skills and knowledge involved in the craft of making huge batches of good quality malt. The maltster's rub, whereby the maltster judges when it is ready for kilning, still applies. Ancient skills and knowledge are combined with modern technology.

Malting, he said

"is a process utilised by the ancients to produce palatable alcoholic beverages: ale and beer."

I couldn't agree more.

PS In one of my earlier blogs I've asked:  where have all the malting floors gone?

Saturday 24 September 2016

a morning with maltsters, part three: on the tour, some archaeological thoughts

We left the meeting room of the Highland Park Distillery and started our tour of the maltings. I'd forgotten my camera, however it gave me the opportunity to make notes and think a bit about the archaeological evidence for making malt.

This was not my first tour of a malting facility. Years ago, when I started my post graduate research into the archaeology of malt, ale and beer I contacted Thomas Fawcett and Sons, Maltsters, in Castleford, West Yorkshire and asked if they could show us round. They were very helpful and friendly. Soon we had been given a personally guided tour of the maltings by James Fawcett himself. Fawcett's make malt for the brewing industry using traditional floor malting techniques as well as having modern Germinating Kilning Vessels. There's a short film on their website where the ancient craft of floor malting can be seen. We'd wanted to see how an industrial maltings worked, having already visited an 18th Century grain barn at the Corrigall Farm Museum, Orkney, with a threshing floor, malting floor and grain drying kiln. Making malt is the same process, whether you are in a grain barn on a farm or at an industrial floor malting. The only difference is the scale of the task.

The tour of the Highland Park Maltings began with the steep tanks. Barley is steeped in water with regular air rests. Air is bubbled through. Steep tanks vary in size, obviously, but the basic principle is to get the barley wet enough and aerated sufficiently to trigger the germination process.
the steep tank, barley in bubbling water, with regular air rests
source MAGB

Steep tanks emulate a traditional and probably ancient technique. Maltsters in history and prehistory would have put their harvested grain into a porous bag and then left it in a shallow bubbling stream for a few days. This practice would, of course, leave absolutely no archaeological evidence. I was first told about it by an Orcadian farmer, maltster, brewer and crofter, Harry Flett, who was the custodian of the Corrigall Farm Museum.

a babbling brook, plenty of water and oxygen here
source wikipedia images
In Britain, people began to grow barley and wheat around six thousand years ago. This was the neolithic era, when hunter gatherers settled down and grew crops. What were they doing with the grain? How were they processing it? The consensus of opinion in academic archaeological literature and belief is that, since the earliest neolithic, they were grinding it into flour to make bread. Perhaps they were boiling it up to make porridge or gruel. The possibility of making malt has not been taken seriously. Many archaeologists, including professors, have shouted at me when I've made this suggestion at conferences. They don't like the idea of making malt in the neolithic.

I've written about some aspects of my research into neolithic grain processing, grain barns and the "first farmers" in an earlier blog. Many of the neolithic rectangular timber buildings in Britain and Ireland were situated beside or close to streams and rivers. Carbonised barley grains with missing embryos have been discovered at a number of these ancient sites. I think that they are good candidates for grain barns and malt houses five thousand years ago.

The steeped grain is transferred to the malting, or germination, floor. This is where it begins to grow visibly. Conditions have to be right. It's too hot in the summer months for floor malting, however, with the modern GKV systems it's now possible to make malt every day of the year. At an industrial floor maltings there are large amounts of grain to be carefully transferred from one place to another. We were introduced to the malt chariot.

steeped grain goes into the chariot
source here
from steep tank to malting floor
source here

According to Distillery Manager Marie Stanton, a malt chariot is a tricky thing to learn how to drive. The maltsters are experts at it, of course. An industrial floor maltings has to deal with large amounts of malt which is couched, then spread out on the floor. The chariot at Highland Park was in use regularly for this purpose. Ambient temperature and weather conditions dictate the depth of the grain bed.

There were several wooden malt shovels, or shiels, leaning up against the wall. They are used to turn the malt. It's a long job and in an industrial maltings like this, team work is crucial. It takes hard work and skill to turn tons of malt on the floor using one of these. On the tour we were told that some maltsters at the Highland Park were ambidextrous, able to turn malt to the right and to the left with ease. Others preferred to just work one way, which seems to be how the owner of this well worn malt shovel worked.

A 19th Century malt shovel, well worn from use
source here

As well as wooden malt shovels, fish tail rakes are used. These make the job so much easier, follow the link below the photo to find out why. Raking the malt is not just a skill, it's an art.

A medieval style custom made malt rake, with fish tails, used by Riverbend Malt House
How did neolithic and bronze age maltsters turn their malt? What did they use? They had no metal rakes. Wooden tools rarely survive in the archaeological record. I've sometimes thought that an animal's shoulder blade might have been a suitable tool. A scapula is a sturdy thing, it has the shape of a shovel and could be used for many tasks that the "first farmers" needed to do. It would do the job of turning the malt nicely. Has anything been found that might support this idea? There's only one discovery that I know of. During road works in 1987 at Achavanich in Scotland, a female cist burial dated to the Bronze Age was discovered. It had contained the crouched burial of a young woman, however only the skull and a few bones remained.

The grave goods that accompanied this young woman were these: a beaker or food vessel, a thumb nail scraper, two flint flakes and, unusually, the shoulder blade of an ox. The beaker or food vessel had organic residues within it. This is another rare find. According to the official site records (HER)

"The contents of the beaker were analysed by Dr Brian Moffat of SHARP who, from a preliminary examination, suggested that it contained: prepared cereal grain, honey, added flowers and fruit (including meadowsweet, bramble & wood sage), and the sap of birch and alder trees."
Similar residues have been found in other bronze age pots and have been identified as the remains of ale. These two things combined, the pot with cereal based residues and an ox shoulder blade, suggest to me that the woman may have been a maker of malt and ale. She had been buried with the necessary equipment. I mentioned this to a couple of people on the tour and they agreed it could be a possibility. The young woman who was buried 3700 years ago is now the subject of a new investigation by archaeologist Dr Maya Hoole. The details are here if you are interested.

ox shoulder blade from the Achavanich burial, was it used to turn the malt?
source here (this is a screen grab from the Facebook page)
The next part of the tour took us to a small room, the laboratory, where the viability of grain for germination was assessed. Why does it need to be tested before it is steeped and turned out on the malting floor? Because barley has a latent dormancy after harvest. It must be stored, in a dry place, for a few weeks or months before it will germinate. The reasons for this and the biochemistry behind it are not yet fully understood. The length of dormancy can vary between crops and barley variety. Traditionally, grain has always been left for a while after harvest. People have known about latent dormancy for a long time.

Grain that will not germinate is useless to a maltster. Upon delivery, samples are taken from every batch of grain. Individual grains are selected at random and tested for viability. This can be done by steeping them in a solution of hydrogen peroxide at 0.75% at 18-21 degrees Centigrade. Germinated corns (seeds) are counted after three days. For a working maltings, this takes too long.

A quicker method of checking viability is to cut a grain longitudinally and use tetrazolium chloride which stains the embryo pink. The maltster can get a result in half an hour. There was a very nice little grain cutting machine in the laboratory at Highland Park, used to cut grains in half for testing from every batch of barley. Shame I forgot my camera, but here's a picture of a stained living barley grain from the MAGB website. Pink toed barley, that's what the maltsters call it, if the barley has a pink toe then it's good for making malt.
white endosperm, pink embryo, it's alive!
source here

The final part of the tour was to climb the old narrow wooden staircase, it was more like a boxed in ladder, to look at the kilning floors in the loft. We were treading in the footsteps of maltsters past, it was a strange feeling. The steps were worn, malt has been dried here, in the same way, for two hundred years. We looked through the window to see the green malt, steaming as it began to dry. It looked very much like the photo below. Drying malt on this scale takes three or four days. The maltsters turn it at regular intervals so that it dries evenly. Hot air and peat smoke from the fire downstairs passes along the flue and through the bed of wet malt, imparting flavour, drying it gently so that the malt is not killed.

green malt at Highland Park, steaming on the kiln floor as it slowly dries
source: a blog by the whiskyspeller's here
We left the kilning floors by a small door which led us onto a metal walkway on the roof, right beside the distinctive pagodas. Whenever the malt is being dried there is steam coming from the pagodas. We had great view over Kirkwall and a new perspective of the Distillery, a place that we often drive past. 

the twin pagodas of the Highland Park Distillery
source here
Finally, we went down the metal staircase on the outside of the building to see the kiln fire downstairs. The maltsters start the fire with coke to warm the kiln, after this, peat from Hobbister is used. The peaty smoke flavours the wet malt. Coke is used at the end to thoroughly dry the malt. Each fire needs to be run slightly differently, depending upon the batch of malt. It's just another of those maltster's skills that can only be learned by experience and practice.

the kiln fire, it's a long way from the malt and there's a metal flue
This kiln has a fierce fire but is situated a long way from the malt. In a pot kiln, you need great heat to fire the pots. The principle with a grain or malt drying kiln is completely different. Hot air and smoke pass along the flue and through the bed of green malt. There are sturdy metal linings to contain the sparks and make it safe. I don't want to go into any more whisky making details. My interest is in making malt for brewing ale and beer. 

Today there are many different kinds of malt being made by maltsters for brewers. It can be confusing for a non brewer. The most crucial is the base malt, the one that is made and dried like this, carefully and slowly to keep the starch converting enzymes alive. These enzymes are needed in the mash tun. Base malt provides all the necessary sugars for fermentation. Other malts, such as crystal malt or chocolate malt have only been made since the mid 18th Century. Just to confuse the issue even further, there is also roasted barley, which is not malted at all and which gives dark beers like Guinness and porter their distinctive black colour and flavour. Hops add bitterness and other flavours, they are also antimicrobial. Unroasted barley alone cannot be used to make beer, it is added to the base malt. Unroasted barley has no enzymes.

Specialist malts provide colour and flavour to the finished ale or beer. They are a modern thing; making roasted malt is not a prehistoric technology. Specialist malts are roasted at high temperatures that kill all the enzymes, therefore it is not possible to make beer using only this kind of malt. I shall have to write something later about this, it's a huge subject. 

Malt is a mysterious thing to most people. In the world of archaeological and anthropological literature I find few references to malt. There is very little meaningful discussion of it.  Assumptions have been made that malt is "toasted roasted barley sprouts". Another belief is that the archaeologist has to actually find "sprouted barley" with roots and shoot still intact for there to have been malting and brewing at their site. I have been told this many times by archaeobotanists. The reality is that the malt loses its' roots and shoots in the kiln. An archaeologist will not find them. There are many other indications that grain has been malted.

When you read the academic archaeological and anthropological literature about "alcohol production in prehistory", there is a belief, an assumption, that all you have to do is mush up a few sweet things, like berries, honey, some sort of sweet plant, maybe a bit of barley and some birch sap. Leave it in a bucket or a pot and, magically, you will have "some sort of alcohol". Making ale and beer is not like that at all. Malt is the essential ingredient. It provides both flavour and, more importantly, the necessary fermentable sugars without which there will be no ale. No beer. 

That's more than enough for now. I shall continue working on my post about alcohol production and some of the myths that surround it in the archaeological and anthropological literature. I look forward to comments and discussion with about malt in the future. Malt matters.


Here's a bit more that I've written about malt, malting, the history and the archaeology. I shall get around to tagging the blogs soon so they are easier to navigate.

Brewer & Distiller International February 2016
The craft of the maltster  
Food & Drink in Archaeology 4 eds Howard, Bedigan, Jervis & Sykes
grain dryers, malt kilns and malting ovens

Friday 16 September 2016

a morning with maltsters, part two

Making malt involves a huge amount of knowledge, skill and experience. This is the second part of my write up of an Orkney Science Festival event that I was fortunate to attend. Making Malt took place on the morning of 7th September at the Highland Park Distillery, Kirkwall. If you haven't read part one, see here.

There were twelve tickets available. Malt, malting and the history of the craft is something that I'm particularly interested in, so I bought two tickets on the first day that they were available. Well worth it. The second presentation of the morning, by Distillery Manager Marie Stanton, was about the practice and techniques of floor malting. She gave us a fascinating insight into the craft.

To make good malt, she said, you need good quality barley as well as common sense, experience, commitment and an unnatural obsession with the weather. The first four things seem obvious but, the weather? What's that got to do with making malt? Malt is a living thing, it requires careful handling and processing. The maltster needs to be very much aware of the weather, looking after the barley on the floor as it begins to germinate and adjusting things accordingly. In cold weather, the barley is couched, or heaped up deeper on the floor. In warm weather, such as the day the seminar was held, they had been raking it out thinner, to cool it. The grain generates heat as it germinates on the floor.

This is the ancient craft of floor malting, a craft that has been around for thousands of years. Decisions about length of steep, depth of bed and readiness for the kiln are based upon years of experience, knowledge and skill.

The steep is about more than just getting the barley wet before it goes onto the germination floor. Water temperature is important, as well as several air rests. Grain left in water will drown and be no good for germination. The idea is to rehydrate the harvested and stored grain up to about 45% moisture.

When sufficiently steeped, the grain is couched, spread, turned and raked regularly according to temperature and conditions. It begins to germinate. This might sound straightforward, but there's more to it than you might think. I'll write about this in the next blog, the tour of the Maltings. When we were visiting, malt was drying in the kiln but there was none on the floors.

steeped grain on the malting floors at the Highland Park Distillery, Kirkwall, Orkney
source: undiscovered Scotland where there is more about floor maltings

The presentation on Making Malt continued. Bowls of barley were passed round.

One contained freshly steeped barley. It had the aroma of wet grain, as you might expect. Another contained barley that had been on the floor and had begun to germinate. This had a pleasant, fresh, almost floral aroma which is hard to describe. The two bowls had very different aromas, although they were just a couple of days' processing apart. This was something I did not expect, these aromas of germinating barley.

There is some complex chemistry going on inside the grain as it begins to germinate. If you want to know more about the biochemistry and physiology of grain germination, there's a reading list at the end of the blog.

The purpose of germination is to allow the embryo to grow, just a little. Enzymes develop and begin to degrade the beta glutens, proteins and cell walls. This is known as modification. When the grain (green malt) is sufficiently modified, it's ready for the kiln.

The malt is dried slowly and gently, to preserve the enzymes. They will be needed in the mash tun. Although there is a fierce fire, the malt is not put directly above it. Hot air and smoke from the fire needs to pass along the flue and through the bed of malted grain, drying it gently over several days. The malt steams as it dries. Both peat and coke are used as fuel. The wet malt takes on flavour from the peat smoke. It's turned regularly in the kiln, to ensure an even drying process. The maltster does not want the malt to be too dry, does not want roots, but they do want plenty of enzymes. It's important to know your kiln, we were told. Each one is different and the drying of the green malt from the floor is a matter of great skill, experience and knowledge.

After kilning, the malt needs to rest for a few weeks before it is used. There was some discussion in the room about why this should be and why it affects the flavour. It seems that the complex chemical processes of this resting period are still not understood. There was general agreement that rested and unrested malt should not be mixed together. 

At the end of the presentation, a bowl of the finished malt was passed round. We were told that we could have a taste.

It was delicious, each malted grain imbued with a peaty, smoky aroma, very good indeed.

Next, the tour of the maltings. We saw bubbling steep tanks, malt chariots and shiels. We saw the malt, steaming in the kilns. As we went in I realised I'd forgotten my camera. I made notes, not just about what we saw on the tour, but also some thoughts on origins of this ancient craft and the potential archaeological evidence for it.


After completing my Master's in 1999, I tried to get funding for a PhD looking into the history and prehistory of malting and the archaeological evidence for malt. I didn't get any funding, but I did get to spend several years preparing funding applications. I worked with brewing scientists and therefore I had access to their library at UMIST, Manchester, where I read up on malting and brewing science, grain germination physiology. I can't say that I understand it all but I learned a lot. 

Here are a few books that cover the subject in detail:

Bewley and Black 1994 Seeds: Physiology and Development
This is about all seeds, see the chapters on barley, barley germination, malting

Dennis Briggs 1998 Malts and Malting
This is what maltsters call “the bible”.

D E Briggs, R S Stevens, Tom Young, J S Hough 1981 Malting and Brewing Science: Malt and Sweet Wort, Vol 1, Springer US
There is a second volume on hopped wort and beer.

Saturday 10 September 2016

a morning with maltsters, part one

The Orkney Science Festival is held annually. It's always a great week of varied and interesting events, talks, demonstrations and fun. This year there was a Malt and Malting seminar with a special tour of the Maltings at the Highland Park Distillery, Kirkwall. There were only a dozen places available and we were lucky to get tickets. We spent a fascinating morning with malting, brewing and distilling experts. It was all about the malt.

Making the malt for brewing and distilling is exactly the same process. The difference in processing techniques happens after the mash tun. A brewer takes the sweet liquid from the mash tun, calls it "wort" and adds hops or herbs, then ferments it into beer or ale. The distiller takes the sweet liquid, calls it "the wash" ferments it into alcohol and then distils it. The wort and the wash are two names for the same thing, the sweet liquid that is obtained from the mash tun. Every brewer who makes ale or beer from the grain knows what wort is because they work with it. People who have never made an ale or beer from the grain are perhaps a bit confused about what it is.
wort or wash?
Depends if you are a brewer or distiller.
source here
Dr Tim Dolan gave the first talk of the morning, explaining the fundamental aspects of what malt is, the biochemistry of malt, how it is made and a little of the history and development of the industry. His career in the malting and distilling industry goes back 40 years and he now teaches the subject. The other speakers were Marie Stanton, Distillery Manager of the Highland Park. She shared her knowledge of floor malting, then led us on a wonderful tour around the Maltings. The third speaker was Eric Walker, recently retired, a man with a distinguished background in all aspects of the malting, brewing and distilling industries. He talked to us about the prehistory and history of making malt and explained some technical details. They were quite a team and between them they had a huge amount of knowledge and experience of making malt.

"Malting is a process utilised by the Ancients to produce palatable alcoholic beverages: ale and beer"  (Eric Walker)

In previous years there have been talks about brewing and distillation, usually organised by the Institute of Brewing and Distilling. Tim told us that he thought it was about time there was a Science Festival event about malt, the Cinderella subject, because malt is the crucial ingredient for ale, beer and whisky. What is malt? It is grain that has been germinated under controlled conditions, then dried carefully in a kiln. Making malt has been a skill, an art and a craft for a very long time. Over the years I have given a few talks at the Science Festival. I was pleased that Tim remembered me and had been to my presentations on malting in prehistory, neolithic ale, grain barns and my most recent "Where were the Viking Brew Houses?" a couple of years ago.

The advent of the combine harvester in the 1940s transformed the grain harvest. The ancient and traditional way of harvesting grain by hand was extremely hard work, it was a time when the whole community worked together to bring the harvest home. On Orkney, where I live, grain was harvested by hand and stacked in stooks in the field until as recently as the 1950s. In case you don't know what a stook is, I looked online and found this painting by British artist Heywood Hardy (1843-1933). Painted in 1872, it depicts a typical scene of the time. I like the detail of the stook and you can see how they were made. The effort and hard work involved in making them can only be imagined.

 Corn Stooks by Bray Church by Heywood Hardy (1872) see here

This oil painting was done just a few years before Henry Stopes published his book about Malt and Malting, an Historical Scientific and Practical Treatise in 1885. It is now available to read online. Oxford University took the trouble to scan it in, many thanks to them for that. I first read it when I borrowed a copy from a brewing scientist when I began my research. It's such an important book and it is an excellent snapshot of the malting industry in the late 19th Century. Henry Stopes mentions the work of Louis Pasteur, who had recently published his work on Germ Theory which was to make such a huge impact on the brewing industry.

But I digress. Let's get back to the talk about malting.

Tim explained the biochemical processes of germination, with the embryo being the living part of the grain and the endosperm being the starchy food store. Malt, he said, is a living thing. It must be handled and processed carefully and correctly by the maltster. This was a point that was made several times throughout the morning. First, the harvested grain is steeped in water. It's crucial to allow air rests. The steep tank is drained of water at regular intervals. If the grain is left in water without air rests it will drown and this means that it will not begin to germinate.

Thanks to scientific research into grain germination physiology and biochemistry which began in the 1960s, we now know that when grain is  sufficiently wet and aerated, gibberellic acid is released from the embryo and the aleurone cells. This stimulates enzymes which convert the grain starch into sugars, the food source for the plant.

All grains can be malted. Barley is considered to be the best grain for malting but wheat, rye and oats can also be malted. Here's a useful diagram of the internal structure of a barley grain in the early stages of germination.

ancient malt and ale : malting and mashing

The craft and skill of the maltster lies in getting the grain to start growing, but not too much. This is known as modification and there is some excellent and detailed information about what malt is and how malt is made on the Maltster's Association of Great Britain web site.

The Highland Park has three traditional malting floors where the grain is spread out after steeping. Raking and turning the malt is a crucial part of the process. We were told that this helps to maintain an even temperature and it also prevents rootlets from tangling. On the malting floor the barleya malted barley grain more details here begins to germinate. When the maltster sees the root and shoot being about four fifths the length of the grain, it is sufficiently modified and ready to be carefully and gently dried in the kiln.  a malted barley grain more details here

Modern techniques of making malt involve the use of Saladin boxes and drums. There are also huge germinating kilning vessels which can make three to five hundred tons of malt at a time. All year round. The quality of the malt can be controlled because it is easy to maintain precise temperatures and levels of moisture. The third speaker of the day, Eric Walker, gave an interesting talk about the industrialisation of malting and I'll write that up later. In the meantime, here's something I wrote about where the malting floors have gone.

Barley is self pollinating. Dr Tim Dolan emphasised this several times, but I wondered why was he making this point so many times? It was because it's so significant in understanding barley breeding. There were not so many varieties of barley in the past as there are today. The science and practice of cross breeding barley began at Warminster Maltings in 1904. This was news to me. Rather than tell you the story myself, here is the account from the Wiltshire Community History web page:

"The most famous name in local malting was that of Dr. Ernest Sloper Beaven, and his reputation is international. He was born in 1857 to a Heytesbury farming family, who moved to Boreham Farm at Warminster in 1868. Beaven said that he began to observe barley closely from 1878 and he became associated with Frank Morgan, Warminster’s leading Maltster. Beaven’s first experiments had been with onions and potatoes but from 1900 he was growing, selecting and crossing barley from seven initial different ‘races’. In 1904 he acquired fields on the Boreham Road for a nursery and in 1914 he launched ‘Beaven’s Plumage Archer’ strain of barley and continued with seed trials for the next 27 years. Beaven could claim that 85% of the total U.K. acreage of barley was grown from the progeny of just four plants, three of which had been selected in the nursery at Warminster between 1900 and 1904."

In the last one hundred years or so, much has been learned about barley and the biochemistry of germination, however, there is still much to be learned. Although some of the mystery and magic of malting has been studied and explained by scientists, some things about barley are little understood.

One of these is latent dormancy. Someone in the group asked about this and the answer was that it is still a bit of a mystery. There is a practical tradition of leaving the grain for a while between harvest and steep, because it will not germinate. This could be about variety, or it could be seasonal. The best thing I can suggest, if you are interested in finding out more about latent dormancy, is to search for the academic and scholarly papers on it. There are quite a few of them out there.

The next talk was about the skills, techniques and practicalities of floor malting and the turn of Marie Stanton, Distillery Manager, an experienced maltster at a number of distilleries. And then there was the tour of the Maltings.

There is only so much detail that one blog post can take, so I shall leave you with a picture of the malting floor at the Highland Park Distillery, Kirkwall, Orkney. It is taken from Wikimedia Commons. I forgot to take my camera to the seminar, but I did take plenty of notes, so I hope this will suffice while I get down to writing part two, while it is fresh in my memory.

File:Highland park malting floor.jpg

Sunday 17 July 2016

big pots: fermentation and storage

Brewing ale in Neolithic Britain - it seems to be a controversial topic among some academic archaeologists. I'm not sure what the problem is with malting and brewing ale in the neolithic era. It could be that few people understand the processes involved in the transformation of grain into malt, wort and ale.

If you have come to this page via the BBC Earth website, or from the Stone Pages, please be aware that the comments attributed to me there are wrong. I have no idea where they came from, other than as a misunderstanding. I hope for a correction in the near future but so far I am not having much success.

Roasted malts, also known as specialty malts, are a feature of modern industrial malting. I'm working on a blog about that at the moment and will post a link to it when I have completed it, hopefully before the Yule celebrations of 2016!

The last few posts have been about explaining the saccharification in the mash tun, where the crushed malt, when mixed with water and gently heated, is converted by enzymes into malt sugars. I've also written a little about lautering, sparging and how to collect the wort.

We've been asked 'why not ferment in the trough. Why go to all the trouble of trying to collect a wort without bits in it?'

Firstly, alcoholic fermentation requires anaerobic conditions. A large vat (1000s of litres) within a building has a blanket of carbon dioxide over the fermenting beer, as in lambic brewing. A small trough (100s of litres) situated outside would have this blanket blown away. Secondly, during fermentation, the little bubbles of carbon dioxide produced by the yeast, stick to the smaller particles and lift them into the froth of the barm. You can see the towering barm in the picture below. It can turn into a really messy monster when it has a lot of little bits in it. After fermentation you would still have the problem of straining or filtering what brew has not been lost to the froth-over. That is a lot harder with little bubbles in it. A bed of husks will not form properly and filtering just doesn't work. 

Inoculating the wort: starting a fermentation
Once the brewer has obtained a quantity of wort by mashing, lautering and sparging, the next stage of the brewing process is the fermentation. Whether you mash in a large pot, a wooden tub with a spigot hole, in a trough in the ground or in a modern mash tun, the wort that you make must be dealt with promptly to prevent infection setting in. Wort does not keep well. Either you boil it, as is necessary with hops, and then cool and inoculate with yeast at the right temperature. Or you can inoculate a fresh wort when it has cooled, and then add the herbs. We found that meadowsweet flowers inhibited the yeast and are better added after the fermentation. To find out more about raw ale which, basically, is beer made from an unboiled wort, I suggest a look at this blog. Raw ale is a huge topic in itself.

fermentation in close up, this is the barm (foam) on a fermenting beer

There are a number of ways of adding the yeast to the wort to start the fermentation. Today, the brewer can add yeast directly, in dried form or as a yeast starter, when the wort temperature is just right. Many modern breweries keep their yeast starter in a fridge. They scoop some of the barm (foam) from the top of the fermenting beer and then store it in a cool place until required. The yeast culture can be kept and used for several months. 

Brewers in history and prehistory could also have used this simple and basic technique, keeping their barm/yeast culture in a cool place. In the 1980s, archaeologists found a medium sized grooved ware pot which had been sunk into the ground in the remains of one of the buildings at Barnhouse, Orkney. The pot, about a litre in volume, had been buried up to its' rim. Analysis revealed that it had contained some kind of 'cereal based mixture', but they were unsure about the pot's function. I think it may have been a barm pot. It was located in a large building, numbered eight by the excavation team and interpreted as a 'temple' or some other kind of ritual building. There were drains as well as many sherds of broken or smashed Grooved Ware pottery, representing pots of about one litre in volume. There was also evidence of feasting and what archaeologists refer to as 'ritual activity', although what that was is not made clear in the excavation report.

I would say that if an archaeologist is looking for a prehistoric ritual activity then the mysterious and magical transformation of grain into malt, wort and ale is well worth considering.

In Norway, Lithuania, Latvia and other places, the tradition of making farmhouse ale survives, with brewers passing on their skills, techniques and knowledge to their descendants. Old traditions of inoculating the wort are still practised in several areas of northern Europe. The picture below shows a wooden yeast ring or kveikering being used to inoculate a yeast starter.

wooden yeast ring or kveikering (photo from the beer blog of Lars Garshol)

Some sources say that the tradition of the kveikering dates back to the 18th century, although I wonder whether the concept might date even further back. It's difficult to be sure because, of course, a wooden object used to gather yeast and start a fermentation would not survive in the archaeological record. In the Viking era, apparently, a stick was used to stir the fermenting wort. This would put yeast onto the stick. Then, if it was kept dry, it could be used to start the next fermentation by stirring a fresh wort. In the Western Isles of Scotland there is a tradition of stirring the fermenting beer with a hazel stick (or wand) which is then hung up to dry and used to stir the next batch of wort, to begin the fermentation.

We did some experiments using a wooden spoon and found that this technique works perfectly.

harvesting barm from the fermentation vessel
barm/yeast drying on the wooden spoon (more photos here)

Big pots as fermentation and storage vessels.
The neolithic era was the time of the 'first farmers'. The earliest grain agriculturalists of the British Isles (c4000BC onwards) were also the megalith builders. They created magnificent stone circles and henges as gathering places for the community. They built stone tombs for their dead and they began to settle down. Associated with the 'first farmers' is the integrated 'cultural package' of grain cultivation, the management of domesticated animals (cows, sheep, goats and pigs) and the manufacture of ceramics. This was the 'neolithic revolution', a different lifestyle to the mesolithic hunter gatherers who had roamed the land for thousands of years previously. At this time in prehistory, the technology for making large stave built wooden vessels (vats, tubs, barrels) did not exist.

How did these neolithic 'first farmers' process their grain? Were they grinding it into flour, to make bread? Were they boiling it, making some kind of gruel or porridge? Or were they making ale from it, by malting, mashing, sparging and fermentation? For some reason, the possibility that such a thing as ale in the neolithic is considered to be a controversial idea by many archaeologists. I'm not sure why. 

Some of the large neolithic Grooved Ware pots might have been used as fermentation vessels. They are perfect in both shape and size. One particularly large Grooved Ware pot found at the neolithic village of Skara Brae, Orkney, was around 30 gallons in volume. Most of the large Grooved Ware pots were around eight to ten gallons. They are found at many ritual and feasting sites of the neolithic, in domestic contexts, for example at Skara Brae, Orkney, and at stone circles and henge monuments throughout the British Isles.

What is Grooved Ware? It is neolithic pottery that archaeologists have defined by its' decorative pattern of grooves and shapes on the exterior. Not all grooved ware has grooves; some of it has fancy applied decoration, with blobs of clay and raised patterns. Most Grooved Ware pots are bucket shaped, with a flat bottom. They are found throughout the British Isles, from Clacton to Orkney and Shetland and also in Ireland. Indeed, this style of pottery was first called 'Rinyo-Clacton Ware'. Rinyo being the name of a site on one of the Orkney islands, Rousay. It was a neolithic village larger than Skara Brae. Grooved Ware was also found on the south coast, at Lion Point near Clacton.

Here's one of Stuart Piggott's beautiful and classic drawings of British Neolithic pottery, showing what some of the Grooved Ware pots from the south coast probably looked like, based upon sherds found during excavations on the Essex coast, at Lion Point.


Pottery is frequently found during archaeological excavations. Archaeologists regard it as diagnostic. The discovery and identification of a sherd of pottery gives them a good clue about the date of the site. Neolithic and Bronze Age pottery was not glazed. It could have been waterproofed in several ways, by burnishing or by being sealed with fats, beeswax or milk.

a sherd of grooved ware
Pottery typologies are complex. It's an enormous area of archaeological study and I could not possibly go into every style and type of British Neolithic pottery in this blog. We would be here forever. There's Windmill Hill, Grimston-Lyles Hill Ware, Ronaldsway, Grooved Ware, Unstan Ware, Peterborough Ware, Ebbsfleet and so the list goes on. Most are round bottomed pots, with the exception of Grooved Ware. It took me many months to get to grips with these stylistic categorisations that have been imposed upon pottery of 5000 years ago.

Many bowl shaped pots are interpreted as 'cooking pots'. That seems fairly reasonable. What puzzles me is that whenever archaeologists find a very large pot, or the sherds of a large flat bottomed bucket shaped pot, it is almost always interpreted as a 'storage pot'. I have not yet come across a large pot from the British Neolithic that has been interpreted as a potential fermentation vessel, although some of them have a volume of several gallons and such large pots are often found at feasting sites, for example, at Durrington Walls, near Stonehenge.

If an earthenware pot is to be used to contain any liquid it must be waterproofed. We discovered, in our mashing and fermenting experiments, that beeswax worked very well as a sealant, as did butter and lard.

As a control experiment we tried fermenting mead in an untreated earthenware pot. The fermentation worked well, the room filled with the smell of mead, and the outside surface of the pot was covered in little beads of sticky sweetness. But the final product was disappointingly low in alcohol. It turns out that the alcohol diffuses through the porous pot much faster than the honey solution. This makes an untreated pot pretty useless for creating an alcoholic drink.

Here is a sample of some of the British Neolithic pottery types, as recorded by Stuart Piggott. You can see that there is a wide range of styles. Some have holes in the rim, to secure a covering or lid of, perhaps, leather. Some are deep, others are wide and shallow. I prefer to look at these pots with function in mind, rather than consider only their decoration and style.

Is there any archaeological evidence for the use of large pots for the fermentation or storage of barley wort? 
One of the very best indicators that a pot was used to ferment wort into ale, or for storing the ale, is the identification of beerstone on the internal surface. Beerstone precipitates out of a fermenting barley wort, it looks rather like eggshell. We have a lot of it accumulating on our plastic fermentation buckets and storage vessels.

It takes many hundreds of uses to accumulate a visible deposit of beerstone, but it is a certain proof of fermented wort. Brewers using plastic pipes in breweries often have to clean them of an accumulation of beerstone. It clogs the pipes.

Here is some beerstone from one of our fermentation vessels:

Beerstone has been identified on pots from a Bronze Age site in the Zagros mountains of modern day Iran. At excavations at Godin Tepe a great many pots and jars were discovered, they were stored in the University of Pennsylvania Museum. Subsequent analysis of a yellowish deposit on the internal surface of jars identified beerstone and it is generally accepted as unequivocal evidence for beer brewing. This pioneering paper by Badler, Michel and McGovern, published in 1993, tells the whole story and contains sufficient detail to be able to repeat the tests for beerstone on prehistoric pottery.

I wonder whether any archaeologists in the UK or Europe would consider looking for beerstone on big prehistoric pots? Maybe it is already being investigated. It would be great if this could happen, since this might end the apparent controversy about whether or not a big old pot was used for the fermentation of beer made from a barley wort.


If you would like to make your own kveikering, here is some more information  and details of how to make one. Brewer Martin Warren of the Poppyland Brewery was so impressed by the idea that he made his own.

My conference paper from 1996 "Neolithic Ale: Barley as a source of sugars for fermentation" can be downloaded from my Academia page, here. 

Thursday 7 July 2016

trough, mash and wort

How do you collect the wort when you have mashed in a trough in the ground?

The main problem, obviously, is that you can't lauter and sparge in the same way that you would if you had used a wooden tub as a mash tun with a spigot, or if you had a bespoke lautering and sparging vessel. When the trough is in the ground, it's a different story.

There are thousands of sites throughout the British Isles that archaeologists know as Burnt Mounds. All that remains is a large pile of fire cracked stones and the remains of a trough lined with either stone or wood. If you have never heard of burnt mounds before, I suggest you have a look at an earlier blog which explains what they are and some of the interpretations. Archaeologists agree that they were used to make water hot. This was achieved by heating rocks in a fire then putting them into the trough of water. What you do with that hot water is up to you. There are many possibilities. Some interpretations include bathing, others suggest cooking meat and some archaeologists think that they were used as a sauna. Another function is as a mash tun. With the discovery of chaff and grain in an oak trough excavated in Wales in 2008, a mash tun is a strong possibility.

Trough mashing at Bressay, Shetland

Replica trough at Bressay, Shetland, surrounded by fire cracked stones.





A few years ago, we mashed in a full sized replica stone trough, based on the one from the Bronze Age burnt mound site on the island of Bressay, Shetland.

The original trough and buildings were moved stone by stone, since it was in danger from coastal erosion.

A replica trough and hearth was built beside the Bressay Heritage Centre, for experimental archaeological work. It's been used to dye wool, it has been used as a bath and also as a mash tun by archaeologist Dr Lauren Doughton in her experimental work.

We were there in the summer of 2011 to mash some malt with her when she was working on her PhD about burnt mounds and troughs. 

The weather was rough, even though it was mid July. Buffeted by the wind and rain, we managed to run a mash and collect some of the wort. Our time was strictly limited because we had to catch the last ferry off the island and get back to our tent. A full set of pictures of the day's mashing, collection of wort and the final brew can be seen here on my Facebook page.

Brewers usually want to obtain as much wort as they can from the mash. There is potential for lots of waste from a trough mash unless you can find a way of maximising the wort extraction. The most obvious technique might be to let the grain settle to the bottom of the trough, then scoop the wort out using a jug or a bucket or something like that. It's tricky, as we discovered. Nevertheless, it works. Inevitably there will be bits of husk in the wort. This is not a problem. They will sink to the bottom again and it is easily possible to obtain a clear wort for fermentation from a trough mash.

Locally sourced clay was used to seal the corners of the replica trough before we began the mash.

Water was put into the trough. It became slightly murky, a grey colour from the clay luting that we had used to seal the trough. We were a bit worried, however, we did not need to be concerned because the resulting ale from this experiment was delicious, sparklingly clear and bright, perhaps the result of our accidental addition of clay to the water.

The hot rock rolling team, from the fire into the water.

The technique of rolling hot stones from the fire into the trough of water had been perfected by Lauren and her team in previous runs. Using garden forks and spades, the hot rocks were expertly rolled down the slope and into the water.

When the water reached strike temperature, 50 kilos of crushed pale malt was added to the 200 litres of water and stirred with a garden fork. You know when the water is the correct temperature for the strike, around 74 degrees Centigrade or thereabouts, because this is when you can clearly see your reflection in the water, no ripples, no steam. We double checked with a thermometer.

The strike:adding the crushed malt to hot water.

The saccharification takes about an hour and it's crucial to keep the mash temperature right for that time, adding hot rocks and stirring as necessary. We put a wooden board over the trough, to help keep the steam and the heat in. It was a good conversion of starches into sugars, a successful mash. The finished mash, when settled, was a deep dark brown and it tasted very sweet.

The finished and settled mash - the next job is to collect the wort and ferment it.
For non brewers, I should emphasise that wort is not alcoholic. Sugar ferments into alcohol, starch does not. The saccharification that happens during the mash is a crucial part of the beer brewing process. Fresh wort is very sweet and prone to all kinds of bacterial and fungal infections. On the three occasions when we have been too tired to process the mash after a demonstration, the next morning the mash was fizzy and sour. Wild yeasts and lactic bacteria infections had ruined it. It was useless. Wort must be collected as soon as it is cool enough to take the yeast. The yeast ferments sugars into alcohol. Herbs or hops preserve and flavour the ale or beer.

We were short of time and collected as much wort as was possible. The brewer used jugs, buckets and plastic containers to scoop from the trough. We had, of course, taken the stones out first, when they were cool enough to handle. The process of collecting the wort was hard work and we only managed to get about 6 gallons out of the trough before we had to pack up, load the van and catch the last ferry back to the Shetland mainland.

The brewer collects wort from the trough. The stones have been removed and are on the heap.

The wort was put into a fermentation vessel, yeast was added and the fermentation vessel was kept warm using sleeping bags as insulation. After about four or five days it had fermented into a fine, clear and strong ale. We used a handful of dried meadowsweet flowers as a preservative.

This is how we should have collected the wort
On the ferry back to mainland Shetland we realised that we had made a mistake. We should have piled the stones up in the trough to make a sort of dam, then we could have put the mash to one side and the wort would have been so much easier to collect. This is how the Moore Group archaeologists collected the wort at their trough mash demonstration at the Sixth World Archaeology Conference in Dublin, 2008.

They made a wooden trough and painted the bottom part with bitumen to ensure that it did not leak. They correctly assumed that the University authorities would not allow them to dig a big hole and set their trough in the ground.

Moore Group archaeologists filling the trough with water at WAC 6, Dublin
They heated the stones on a fire, dropped them into the water and added the crushed malt when the strike temperature was right. It was this hot rock mashing demonstration that inspired us to stop mashing in pottery vessels and start using troughs, wooden tubs and hot stones.

Here are some of my photos of the Moore Group's event:

1 heating the rocks
2 heating the water
3 saccharification: the mash

4 the stone dam, mash and wort separated

5 settled wort and mash

6 collecting the wort, it's cloudy because it has been stirred up.

Hot rock mashing is a spectacular process, the stones sizzle as they hit the water, the mash saccharification happens right before your eyes and the aroma from the mash smells delicious. This is a mysterious, magical transformation from grain starchiness into fermentable sweetness. Surely this would have been an event that would have amazed and impressed people in prehistory, just as much as it does in modern times.

Collecting the wort like this, by creating a dam of stones, is an extremely efficient way of doing it, perhaps even allowing for sparging. Once the first runnings have been collected from the trough, more hot water can be poured gently through the mash, thus releasing more wort for the brewer. There would be very little waste and a good quantity of wort could be collected.

Is there any archaeological evidence for the collection of wort like this?

It is rare that prehistoric troughs are excavated with the stones still within them. If you have excavated one like this, I would love to hear about it. Excavations in 2013 by Wessex Archaeology at Kingsmead Quarry, Horton, in Berkshire, England revealed the remains of four neolithic buildings. They were interpreted as having been 'houses', which is often the case with these discoveries. I do wonder how many of these neolithic 'houses' might have been used as barns or as buildings where the grain was stored and processed. But that's a story for another blog.

One of these four neolithic rectangular timber buildings at Horton caught our attention when we were looking at the pictures online. There appear to be some fire reddened rocks close by one of the buildings, in a heap. The buildings are, as always, interpreted as "houses". But were they dwellings? Or some other kind of building, like a barn or grain processing building? See Wessex Archaeology's page about them here

The red rocks look rather like modern bricks. There seems to be no mention or discussion of them on the web page. Maybe I missed it. However the stratigraphy indicates that they are contemporary with the building. So, are these stones an indication of hot rock water heating technology at neolithic Horton? Were they piled up in a wooden trough that has long rotted away? What were the people doing in and around this rectangular wooden building, over 5000 years ago?

I cannot answer these questions. I am nevertheless intrigued by this discovery. And so I finish this blog with a close up (thanks to Graham) of those mysterious fire reddened stones and welcome interpretations, comments and discussion.

a close up of those mysterious fire reddened stones beside the neolithic building at Horton


If you want to know what our Bronze Age Trough Ale, with meadowsweet, tasted like, we sent some to David Connolly of BAJR (British Archaeological Jobs & Resources). Although he struggled to open the parcel, he gave his opinion on the ale's flavour and strength.

It is sometimes said that prehistoric ale was weak, cloudy and sour and that it tasted disgusting. We disagree.

Here is the link:

Quinn, B., & Moore, D. 2009 ‘Fulacht fiadh’ and the beer experiment’ in Stanley et al (eds) Dining & Dwelling. NRA Monograph Series No. 6, 43-53, NRA, Dublin.