Evolution of the Malthouse

Written by Mark on 01/24/17

Brewery tours are great. Not only do I get to enjoy beer at the end, I also get to see all the shiny stainless steel contraptions that churned out that beer. As a home brewer, I at least have some understanding of how the equipment works, but my mind is still boggled by its scale or ingenuity of design. As one person, it feels beyond me.

I did a malthouse tour at Rahr Malting Co. and had a similar feeling: I’m a tiny human. I’m surrounded by massive complex structures that are way beyond me. How did someone figure all of this out?

Like brewing, it didn’t happen overnight. Malting has been around for many thousands of years, so the craft has experienced a long progression of tinkerers and innovators changing its course. Generally speaking, they have sought improvements in three major areas: climate control, labor reduction, and malting speed.

Over the millennia, the maltster has gained greater and greater efficiencies in all of these things. They keep chipping away at that end goal: to make malt faster, cheaper, and more consistently.

And when you look at the behemoth of a modern malthouse, you can’t help but believe that they’ve done it.

Germinating beds at Rahr

Just a small fraction of the germinating beds at Rahr Malting Co.

Early Malting Technology

Technology hardly seems like a fitting word for the first forays into malting, but hey, the wheel was revolutionary once. For early maltsters, their primary challenge was climate control (labor reduction may not have been a concept back then).

Malting consists of three basic steps: soak the grain, let it sprout, and dry it down. Each step requires its own unique climate: cool water for steeping, cool, moist air for germination, and hot, dry air for kilning.

The first maltsters did not control the climate so much as they found the proper environments to malt in, such as a well. They would submerge a basket of grain in the well for a few days, then raise the basket to a cool damp part of the well to allow their grains to slowly germinate over a few weeks. And finally dry out their malt in thin layers in the sun.

This was a slow process, potentially taking up to a month. And it was limited by the access to wells and the like. The demand for beer must have increased (surprise, surprise) to the point where these multi-purpose malthouses were inadequate.

The craft progressed and maltsters started building primitive structures intended primarily for malting. They hollowed out cisterns and caves to fit their needs. Under the city of Nottingham, an extensive cave network was carved out of the soft sandstone, with nearly 30 caves devoted to malting.

Cave map of Nottingham

One of Nottingham’s manmade malting caves that includes a kiln room to roast grains underground. Image by Tony Waltham.

The Reign of Floor Malting

Well into the 19th century, malting was carried out in much the same way as it had always been done, though it moved indoors. The malthouse tended to indeed be a house, often an outbuilding on a farm, which could accommodate all of the steps of malting in one space. These operations were generally floor-maltings, as the grains were spread out and germinated on a large floor.

While labor reduction started to get a head nod, the primary challenge was still climate control. Without artificial refrigeration, this confined malthouse operations to the cooler half of the year.

As the temperature outside fluctuated widely, the maltster could maintain a relatively constant temperature within the grain bed by moving it, piling it up, or spreading it thin. At the beginning of malting, the grain took up moisture in a vat or cistern filled with well water, then was shovelled into a pile on the germination floor. In this initial “couching” phase, the grain would start to germinate and release heat and CO2. Left alone, this heat/CO2 production could lead to uneven growth and lack of oxygen, which can kill the grain.

The maltster dealt with this problem by raking out the pile into a thin layer on the floor several inches deep. They would turn the grain every few hours to dissipate heat and keep the grain’s rootlets from matting together. The grain had to be tended day and night, though the night shift was known to be much less attentive, understandably. Germination time certainly varied, but at one point, it was British law to keep the grain on the floor for 21 days. Modern malthouses germinate in 3 to 4 days.

Once germination finally completed, the grain was shovelled into a direct-fired kiln. Temperature control was especially tricky here, as the fire had to be constantly stoked to the right level and they relied on natural ventilation through a chimney, which changed with the winds outside. Not surprisingly, malthouses burnt down regularly, as there was a perpetual fire raging in a building built with a lot of wood. This problem continued well into the 20th century, with the Mittagong Maltings in Australia devastated by fires in 1942, 1969, and 1980.

Available materials often were not ideal for malthouse construction. The germination floor ranged from beaten earth to wood to tile, all of which were hard to clean. Floor-maltings became a lot more sanitary with the introduction of cement. The kiln floors started out as horsehair cloth, but saw a progression toward perforated clay tiles and finally perforated metal by the late 1800s.

Floor malting went heavy on the manual labor. Just think of every time the grain was moved about the malthouse: first, the maltster would load grain into the cistern, then unload it; couch grain into piles, then break down piles and spread them out; thicken, thin, and turn grain on the germ floor; load grain into the kiln, level, turn, and unload it. Geez.

Historic malting tools

A maltster’s tools: forks, rakes, shovels, etc. Image from Dennis Briggs' Malts and Malting.

It could be an unpleasant job for many reasons. My favorite task of the maltster of yesteryear is turning grain in the kiln, which involved stripping down naked and tying canvas ‘bag-boots’ onto their feet to keep them from burning. Malting expert Dennis Briggs says it well: “turning malts by fork or shovel as often as every 2 hours in temperatures up to 221F in a smoky, fume-filled and dusty atmosphere was not a popular job, even when linked with free beer.”1

Malting Meets the Industrial Revolution

After many centuries of relative stasis in the malting world, the malthouse changed very quickly in the late 19th century. There is a whole host of reasons for the dramatic transition from agrarian floor malting to industrial pneumatic malting.

Firstly, mechanization. With the advent of steam and electrical power and the spread of technologies like the motorized fan and pump, human muscle became an inefficient way to get work done. All the loading and unloading of grain could be done much faster with augers and conveyors.

Secondly, the shift from rural to urban. While for many centuries, a home-based malthouse might only serve the population of a town or village, now there were large enough urban centers to create demand for malting on the industrial scale. Breweries initiated this growth, then demanded a cheap consistent supply of malt to match their operations.

Finally, some events changed malting at a regional level. In the U.S., tastes were changing from hard cider to beer, as German immigrants poured into Midwest cities in the mid-19th century. In Britain, the restrictive malt tax was repealed in 1880, removing many of the regulations posed on maltsters and removing competitive advantage for small malthouses.

The times were a-changing, and the malthouse was caught up in the sweeping tide of industrialization. As John Mallett says, “Iron replaced wood, and malting evolved from a trade where a single person had deep understanding and ownership over every aspect of the process to an industry that was commercialized, profit-oriented, and able to be performed on a larger scale by many unskilled laborers.”2

The Rise of Pneumatic Malting

The limitations that kept manual floor-maltings small no longer existed in the mechanized world. The late 1800s saw a flurry of malthouse patents all claiming they had the equipment that would redefine the malthouse as a modern factory. These inventors focused both on dialing in climate control and reducing labor.

I usually think of the UK and Germany driving the world of beer throughout history, but it was three Frenchmen – R. d’Heureuse, Nicholas Galland, and Jules Saladin – who developed the seminal pneumatic malting technologies.

As the word pneumatic suggests, the ability to control airflow was fundamental to this new type of malthouse. While not working in collaboration, the three inventors built on each other’s pneumatic improvements: d’Heureuse decided to circulate air through the grain bed, Galland cooled and moistened the air with water sprays and ice, and Saladin added a track of helical screws to travel along the grain bed and turn the grain.

Incredibly, “Saladin boxes” are still used as germination beds in malthouses today. They are long, rectangular compartments that can hold a grain bed depth of 3-4 feet. The grain rests on a perforated metal sheet above an empty air space through which humidified, cold air is blown to remove heat and CO2. And those motorized helical screws mix the grain up and break up matted rootlets.

Saladin Box

Diagram of a model Saladin Box. Image from Dennis Briggs' 'Malts and Malting.

The leap from floor malting to Saladin boxes is vast. The grain bed could be 10x as deep in pneumatic malting, so the space requirements of the malthouse were one-tenth what they had been. Then there were those nifty screws that replaced the person who turned the grain every few hours. And the machines could operate year-round in climate-controlled paradise while putting out a more consistent product.

Unsurprisingly, malt producers saw all this progress as a great improvement over the old ways, so they set off at full force to continue the trend of bigger, better, faster.

How Patents Tell the Story

As creators of malting equipment ourselves, my partner Christopher and I spent a lot of time reading through old patents while we applied for our own patent. The proposed designs of the last 150 years range from the elegant to the absurd, and they showcase the trends in factory design.

At first, engineers were figuring out the best ways to harness their newfound mechanical powers. Do we blow air up or down through the grain bed? How can we reduce the amount of time moving the grain between vessels in the malthouse?

They were very concerned with how the layout of the factory could reduce malting time and labor. The larger and larger batch sizes complicated the transport of the grain. By the 1960s, tower malthouses had become popular. They used their vertical energy to drop grain from steep tanks at the top into germination boxes, which fed into kilns below.

Malting tour cross section

Malting tower built in 1983. Image from UK Malt.

Around the same time, continuous malting was catching on to challenge the practice of batch malting. In a continuous malthouse, super slow conveyors moved a never-ending parade of grain through water, cool air, and high heat.

Domalt continuous malting plant

Domalt continuous malting plant in Haddington, Scotland. Image from Dennis Briggs' Malts and Malting.

By the end of the 20th century, malthouses were patenting their CIP (clean-in-place) technologies. With much of the rest of the process mechanized, workers had still been responsible for sanitizing equipment. But no longer. Well-placed nozzles could spray out harsh chemical solutions and further remove the need for manual labor.

In recent years, patents have mostly shifted focus away from mechanical improvements to chemical ones. Scientists have been working on chemical additives to speed up the malting process. The most well-known additive is a hormone called gibberellic acid, which stimulates the grains to germinate. The malting industry is divided over the use of these additives. Recently, the Craft Malting Guild defined craft malt as being made without the use of any chemical additives.

Engineers have thrown all sorts of things at the wall to see what would stick, and plenty of them didn’t. According to Briggs, many designs were tabled because they were excessively complex, too expensive to maintain and clean, or just didn’t do what they were supposed to: climate control.

The Modern Malthouse

The local malthouse for a Minneapolis resident like myself is Rahr Malting Co. in Shakopee, MN. Local does not mean small-scale in this case. With the recent construction of their sixth malthouse, it has become the largest single-site malting facility in the world.

The campus of Rahr Malting Co.

The campus of Rahr Malting Co.

The sprawling campus has huge silos to store the incoming barley and outgoing malt. Its six malthouses were built at different times and represent the different eras of pneumatic malting technology, from Saladin boxes to tower malting. They update their controls and equipment from time to time, but rely on an infrastructure that is tried and true.

Like many other modern malthouses, they aren’t doing things that differently than Galland and Saladin 150 years before them, but what’s changed significantly is the automation they’ve achieved. For example, when temperature sensors in the grain bed read high, automatic controls turn on an additional massive centrifugal blower to push more air through the system. No human needed.

Fewer people are needed to output more and more grain. According to Briggs, in 1983, one person could produce 3800 tons of malt a year with modern pneumatic technology.1 Compare that to 608 tons of malt per person per year from a 1983 floor-malting (yes, some have survived the industry’s shift and mechanized their operations) and you understand why pneumatic malthouses produce the cheapest malt.

The scale of operations at malthouses like Rahr is unprecedented, a seemingly endless ladder of growth. As of 2017, Rahr now produces 460,000 metric tons of malt each year. That’s enough to make 6 billion bottles of craft beer or 12 billion cans of Bud. Most of it will become Bud.

Scale to Explore

The malthouse has come a long ways since the days when it was just a sack in a stream (though that still exists too – thanks for this treasure brought to my attention by Lars Garshol). There’s a lot of cheap consistent malt pouring out of the major malthouses in the world, and that production will only increase as demand for malt grows.

But as you can imagine, there’s not much experimentation going on at this massive scale. The equipment does not allow for it. The stakes are too high when a 250 ton batch could be thrown out. That’s like pouring 2.75 million bottles of home brew down the sink.

There is a growing number of small-scale craft malthouses working with batch sizes of 1-10 tons that are redefining the modern malthouse. Their equipment is a modification of current pneumatic designs, or a revival of the floor malting tradition.

Craft maltsters are producing malts that cannot be attempted at Rahr’s scale. Valley Malt recently shared experimental  Kimchi Malt, Kvaas, Chocolate Maize, and Bourbon Barrel Smoked Malt. But the demands and scales of running a business limit experimentation even at this small scale.

There is another scale that’s possible: the individual scale. That’s what we’re building. A setup that is compact that goes beyond the features of a modern pneumatic malthouse: precise climate control, automated operation, and the flexibility to give one person the creative control of an entire malthouse without any of its pressures.

With our equipment, you can explore the possibilities of malting at a scale that the individual can manage. At the end of the day, if your experiment goes awry, you’ve gained 25 lbs of compost. If it goes well, you may have created a new type of malt.


  1. Malts and Malting by Dennis Briggs. 

  2. Malt: A Practical Guide from Field to Brewhouse by John Mallett.