“Isn’t that a coffee machine?” Koen said when he looked at the BrewZilla. A little later he was roasting Szechuan pepper in a small pan, and for a brief moment his hop-forward brewery in Amersfoort smelled like citrus, pepper and a small experiment that felt bigger than nineteen litres.
This is Pro Goes Homebrew. A Kegland story series in which we challenge pro brewers to brew a beer on a small kettle. How do they work? What happens when routine and scale fall away? And what can we, as homebrewers, learn from their craft, curiosity and experience?
The disease
When we arrived in Amersfoort, Rock City was closed to the public, but the brewers were calmly having coffee. Owner Koen Overeem opened the door and welcomed us in. Together with his brother, he runs this hop-forward brewery on an industrial estate in Amersfoort. Known for its hoppy hazy beers and endless collaborations with brewers all over the world.
Koen is creative to the core. He talks with genuine enthusiasm about the successful crowdfunding campaign, the renovation of the warehouse, the start of several spin-off businesses and “the disease”, as he calls it when he talks about coming up with ideas. Not because he enjoys collecting ideas all day, but because he almost automatically sees where something rubs. An unsafe ladder. A clumsy task. A margin that could be better. A collaboration that could be set up more intelligently. Where others think: this is how we do things here, Koen thinks: why, actually? No wonder he became chair of CRAFT, the Dutch trade association for independent breweries. This is someone who connects people and travels the world to learn from other brewers.
“Are we going to brew on that coffee machine?” — Koen
Koen is open to almost anything. If you have a question or a wild idea, Koen switches on. When we asked whether he wanted to brew a batch on a 35-litre kettle, his answer was immediately positive. Or on the coffee machine, as Koen called it. A small stainless steel thing with hoses, pumps, displays and attachments, right in the middle of a brewery between 5,000-litre tanks and an actual Catwalk that lets brewers safely dry-hop into tanks six metres up. Another one of Koen’s ideas..
This brew day became a collision between small and large. Between sticky manual work and professional infrastructure. Between a nineteen-litre Szechuan Saison and a brewery built for scale, safety and speed. And that is exactly where Koen’s way of looking becomes visible. He is not the brewer who starts with the display, the plug or the manual. He starts with the question of what he wants to make, why he wants to make it and what the ingredients need to do to get there.
“I’m not technical support. I mainly want to understand what the ingredients do and why, so I can choose what I want to make and why.” - Koen
The recipe we put in Koen’s hands was relatively simple, but also classically by the book. Saison yeast. Szechuan pepper. One hop variety. A dry beer, while Rock City is best known for hazy, silky, oat-heavy IPAs. Milk, milk and white. That is how Koen described their ideal New England style. Perma-haze. Lots of oats. Sometimes as much as 50% of the grain bill. And now he was standing next to a small kettle that could not hold its temperature tightly, brewing a bone-dry beer he had not chosen himself.
🧾 Recipe: Szechuan Saison
A 5% Saison, brewed on the BrewZilla 35L Gen4 using the no-sparge method.
- Batch size: 19 litres
- SG: 1.048
- FG: 1.010
- Colour: 16 EBC
- IBU: 23
- Carbonation: 3.3 CO2-vol
- Boil time: 60 minutes
- Mash water: 28.32 litres
- Sparge water: 0 litres
- Grain bill: 2.5 kg Pale Ale 2-Row, 1 kg wheat malt and 500 g BEST Melanoidin
- Hops: 25 g Epic as first wort hop and 50 g Epic at 5 minutes
- Water profile: Amersfoort tap water → Saison, sulphate/chloride ratio 3.1
- Brewing salts: Epsom Salt, Gypsum and lactic acid in the mash
- Flavouring: 20 g Szechuan pepper in the final 5 minutes of the boil
- Mash schedule: 63°C for 60 minutes, then 78°C for 10 minutes
- Yeast: 1 packet of Lallemand Farmhouse
- Fermentation profile: rising from 22°C to 25°C and then 28°C, followed by cold crash and kegging
Optimising is not a need for control
After the mash, it was time for the boil. We did not sparge, following the no-sparge recipe Koen neatly stuck to. While the wort was rolling nicely, we stepped into the brewery kitchen. The Szechuan pepper needed to be roasted. Not complicated, but important. Koen turned out not to be a cook, but he did know where the pans were. Short heat, keep it moving, wait for the aroma to come out. And the moment the pepper warmed up, everyone understood why that step was there. The aroma opened up immediately.
We walked back to the kettle and threw the glowing hot peppercorns into the boiling wort. Behind us stood a row of 5,000-litre tanks filled with Koen’s bubbling IPAs. With the Catwalk as the eye-catcher. Another idea that came from Koen’s brain. The first time he had to dry-hop at height, he was standing on a ladder. Pressure came out of the tank, a rubber fitting snapped loose and hit him.
You could think: that was a close call. Koen thinks: this system is unsafe. We need to build something for this.
He had a local welder build a catwalk. Not a full extra floor, but a walkway above the tanks. So brewers can stand safely. Lift sacks of hops up. Work without a ladder.
That is Rock City in one image. Not just brewing, but building the conditions in which brewing can be done better. Koen calls that “his disease”. He cannot switch it off and will always keep coming up with ideas.
A distribution operation of their own. A keg pool. Collective purchasing. A pasteurisation cabinet for alcohol-free beer, built from an old smoker with steam, PLC control and a cold shower once the right level of pasteurisation has been reached. He comes up with all of it and it helps. Because their beers are high quality and the company is profitable.
That might be the biggest lesson from Rock City: good brewers keep looking. At other brewers. At machines. At friction. At safety. At margin. At flavour. At a coffee machine that may not work perfectly, but immediately raises all kinds of questions.
For Koen, optimising is not a need for control. It is a way to free up attention. The less a brewer has to spend on lifting, spilling, balancing or putting out fires, the more space remains for quality.
“Making things lighter through automation means they can focus on quality, not on doing, not on the little tasks.” - Koen
This is actually kind of sexy
Looking at the Catwalk, a small coffee machine suddenly becomes mildly confrontational. Because brewing on a small scale is physical. Everything is in your hands. Everything is sticky. Everything gets dirty quickly. The temperature shoots up and drops back down. The top plate sits crooked. Grain ends up where you do not want it. The pump miraculously keeps running. You lift something and something else falls back in. Koen said that during a normal brew day, they do not even see the wort. Everything runs internally and they do not touch anything.
The recipe was calculated as a no-sparge batch, with a lot of water in the kettle. In theory, it fit. In practice, it was tight. The temperature fluctuated heavily, sometimes from 63 to 68 or 69 degrees. The sensor was at the bottom, the pump was running, but the system did not behave exactly as you would want. And still it was a good brew day. Maybe precisely because of that.
Because brewing small removes the distance. On a large scale, you move the product through pipes, pumps and valves. At this scale, it is back on your hands.
“Here, moving it around is so small-scale that you’re much more involved with the ingredients. Which, now that I say it out loud, is actually pretty sexy. You really have your hands in it, so everything gets dirtier, everything sticks, everything becomes messier.” - Koen
At Rock City, brewing does not feel like flawless execution. It feels like dealing with what happens. Observing. Adjusting. Laughing and, above all, simply continuing. Having fun and continuing to laugh is the most important thing, according to Koen.
And meanwhile, a Szechuan Saison was boiling away. With Epic hops and Szechuan pepper that had first been roasted in a small pan. Not a big beer. Not a complicated joke. Just a dry, spicy experiment on a small system that gave us something to talk about all day.
🎓 Five tips from Koen
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Optimise your own system
Look at the Catwalk and the pasteurisation cabinet. If you keep doing something awkward or unsafe, it is time to optimise your system. Brewing becomes even more fun when you can work safely and calmly.
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Do not stare blindly at the recipe. Play with ingredients
First decide what you want to make and achieve, then work backwards through reverse engineering. Learning only really starts when you understand what an ingredient does, and you do not discover that by looking at it respectfully from a distance, but by playing with it.
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Take water seriously
Water is the biggest ingredient in your beer, but often the least understood. In this Saison, the water profile clearly leaned towards sulphate, fitting a drier, sharper beer. Great malt and hops matter, but water steers more than many brewers think.
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Rules are not the end point, but the starting point
Do not colour outside the lines because rules are uninteresting. Do it because you want to know who drew those lines, why they are there, and what happens when you consciously move beyond them.
“You can only use this much of it in your grain bill, and I always think: who decides that?” - Koen
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Keep learning from other brewers. Dare to ask questions
Remember that brewers always want to help each other. So go to your local brewery and dare to ask questions. Together, you get further than you do on your own.
