James Harper
Filter Stories - Coffee Documentaries
Coffee stories with an extra shot of history and science. Filter Stories is a podcast revealing coffee’s hidden microscopic secrets, its powerful past, and how your choice of beans impacts tens of millions of people. See the behind-the-scenes stories on Instagram @filterstoriespodcast. If you haven’t already, please subscribe to the show and review us on Apple Podcasts and Spotify!
Where to listen?
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Episodes
Guatemala's Inconvenient Truth, Part 2: Who does specialty serve? 20.04.2026 28:44
Specialty coffee changes the story for the indigenous people of Guatemala. Coffee as a tool of oppression finally offers hope....and then something a bit more complicated. This episode explores the tension between the values of the Mayan communities who grow coffee, and the values that drive the specialty coffee movement. Many of the signals we typically look for in our coffees - super-special...
Guatemala's Inconvenient Truth, Part 1: Whose land is it anyway? 20.04.2026 43:50
When you buy a bag of coffee labelled fifth-generation family farm, it feels like a good choice. But in Guatemala, that label might actually be a signal for a more uncomfortable truth. This episode explores how land has been understood, used, and eventually fought over in Guatemala for centuries between indigenous people, Europeans and those in-between. It’s a story of what happened immedia...
Surrogates: Anything but the coffee 02.03.2026 46:25
What happens when coffee disappears? This is not a thought experiment! It’s happened many times in history: War, blockades, tariffs, ideology, health panics, sanctions, supply shocks. When coffee is not around, people still need something warm, comforting, and familiar. And throughout history, people have reached for coffee surrogates: roasted plants and grains engineered to look like coffee…...
Mother Coffee: The history and heritage of Ethiopia's wild coffee forests 09.02.2026 48:40
Most coffee is grown on vast plantations using machines, pesticides and fertilisers. But in Ethiopia, coffee grows wild in humid forests surrounded by birds. And that wild coffee matters more than most of us realise. It is the genetic ‘library’ we can turn to find new varieties to help us keep coffee thriving in the face of climate change. But the communities who live alongside them and h...
We Built This City…On Coffee: Hamburg and the making of Europe's coffee trade 05.01.2026 50:12
On a long walk through Hamburg, somewhere between the fish markets and giant cranes, you might stumble a giant bronze coffee bean looks like its crash landed from space. But this giant coffee bean represents a staggering fact: one in every three cups of coffee drunk in Europe has passed through Hamburg. In the first half of this episode, we explore the many profound ways coffee shaped one of...
Introducing: Series Three of A History of Coffee 29.12.2025 2:59
We’re back with more stories about the tiny psychoactive seed that changed the world and continues to shape our lives today. Is it possible to follow the story not just to Ethiopia, not just to a single town, but all the way back to one tree? We’ll uncover the uncomfortable history of Guatemala — a story about who inherited the rich volcanic soil, and who was forced to work it. We explore what hap...
Coffee Quality, Part 3: When the “quality” myth hits the farm 08.12.2025 30:00
For twenty years, the 2004 cupping form profoundly shaped the specialty coffee world. But on the hillsides of coffee farms, some of the form’s byproducts have been disadvantaging producers. In this episode, we follow two producers whose lives collided with the myth of universal quality. These stories reveal how a single idea of “quality” can close doors for the people with the least power in...
Coffee Quality, Part 2: How “quality” became a myth 08.12.2025 25:33
If you ask two specialty professionals what makes a high-quality coffee, you’ll likely get a surprisingly consistent answer: clean, sweet, juicy, bright. To an outsider, they would be forgiven for thinking coffee quality is universally defined. But the truth is more sober. In this episode, we examine how a simple cupping form helped create a universal idea of quality. We then look at the evide...
Coffee Quality, Part 1: The birth of specialty coffee flavours 08.12.2025 23:30
For the longest time, coffees were dull and bitter. But then a small group of pioneers changed the world. In this episode, we travel back to the 1960s and ’70s to meet the trailblazers who realised coffees could taste distinctive: sweeter, brighter, cleaner. We discover how their personal preferences became a movement, then a form, and eventually a global definition of “quality”. Please su...
How specialty coffee woke up to water’s role in flavour 28.07.2025 25:39
For the longest time, the coffee community only cared about water’s impact ruining espresso machine boilers and kettles. But what about water’s impact on coffee flavour? In this episode, I tell the story of how the specialty coffee community came to understand water chemistry: the pioneering work of the computational chemist Christopher Hendon and British roaster Maxwell Colonna-Dashwood, the ge...
The two ingredients in water that ruin your coffee, and the ancient story behind them 28.07.2025 38:40
550 million years ago, earth was perfect. We had perfect water for coffee AND we were living in a vegetarian paradise! But then Earth changed—violently. The planet shifted from a peaceful, plant-eating paradise to a darker, more brutal world. And in this new world, the chemistry of water was forever altered. This is the wild story of how earth-shaking forces and the spirits of long-dead critte...
Getting great water for coffee, step-by-step. Part 2: How to measure and treat your water 14.07.2025 43:17
Water massively impacts your coffee’s flavours. But most of us struggle to fix our water because water science is confusing… …until now! In this special collaboration with Lucia Solis ( Making Coffee podcast), I guide her through the two most important concepts you need to understand to get great-tasting water for coffee: hardness and alkalinity. We go step-by-step through: • Why these concept...
Getting great water for coffee, step-by-step. Part 1: Alkalinity, hardness and why it matters 14.07.2025 26:20
Water massively impacts your coffee’s flavours. But most of us struggle to fix our water because water science is confusing… …until now! In this special collaboration with Lucia Solis ( Making Coffee podcast), I guide her through the two most important concepts you need to understand to get great-tasting water for coffee: hardness and alkalinity. We go step-by-step through: • Why these concept...
Farm to port: why specialty costs more 23.06.2025 54:19
Every time we open a bag of beautiful specialty coffee — like Erick Bravo’s from Finca El Chaferote in Huila, Colombia — we’re drinking something that’s been on a long journey. And I mean long! Over 1500 kilometers north up and down the Andes mountain range, a distance more than twice the height of France. Along the way, it passes through dozens of hands, machines, and decisions. We follow it...
Why one Colombian farmer chose specialty, and the other walked away 09.06.2025 46:45
I travel to Colombia’s Huila region to answer a question that’s puzzled me for years: if specialty coffee pays more, is better for the environment, and brews tastier cups—why don’t more farmers grow it? I speak with two producers in the same region whose choices couldn’t be more different. One stakes his future on specialty. The other opts out. Their decisions come down to more than passion or...
The hard business of selling beautiful coffee, part 2 19.05.2025 39:02
Volume. Cheap. Lame flavours. This is the traditional way of growing coffee in Brazil, and almost every farm does it this way. But what if you wanted to produce beautiful, distinctive flavours instead—and make a living from it? In this episode, we travel to Fazenda Paraíso in Minas Gerais, Brazil, where farmer Vicente Pereira and his daughter are on a steep learning curve finding buyers for t...
The hard business of selling beautiful coffee, part 1 19.05.2025 29:08
Volume. Cheap. Lame flavours. This is the traditional way of growing coffee in Brazil, and almost every farm does it this way. But what if you wanted to produce beautiful, distinctive flavours instead—and make a living from it? In this episode, we travel to Fazenda Paraíso in Minas Gerais, Brazil, where farmer Vicente Pereira and his daughter are on a steep learning curve finding buyers for t...
The Speed of Heat: How to roast more coffee, faster! 24.03.2025 52:24
To roast coffee faster, you need to turn up the heat….right? No! In this episode, we explore the three powerful methods of heat transfer that revolutionised roasting. We’ll journey from humble beginnings—when roasting three kilos took half an hour—to machines that now roast hundreds of kilos of coffee in the time it takes you to boil a kettle. But beans roasted at lightning speed look stra...
Coffee Roasting: How baby plant food transforms into delicious coffee flavours 10.03.2025 47:43
A mother coffee plant gifts its baby everything it needs to grow—a green seed packed with food. But when we roast coffee, we hijack that gift and turn it into something else: flavor. But what is flavor, at a microscopic level? What actually happens inside the bean when heat meets those nutrients? In this episode, we shrink down to witness the Maillard reaction up close—a wild chain of molecula...
Fruit juice or creamy almonds? Your guide to controlling cold brew flavors 16.02.2025 46:39
When I started making cold brew this last year, I treated it like hot brew filter coffee. But no matter how I adjusted the grind or tweaked the brew time, I hardly got any differences in flavor… Then it hit me: cold brew isn’t just a slower hot brew—it’s a completely different game with its own rules! In this episode, I speak with leading coffee researchers who break down the microscopic dance...
Hot vs Cold: The science behind temperature and taste 03.02.2025 45:15
For years, I used cold brew as a last resort—the only brew method to tame dark, oily beans that were too bitter for hot water. Then one day, I took a chance on a Guatemalan Gesha and brewed it cold. The result? A massive explosion of florals I’d never tasted before. That single cup sent opened my eyes into how extraordinary cold brew can be. In this episode, I speak with world-leading coffee...
Introducing: Season 3 of The Science of Coffee 27.01.2025 2:03
We’re back with another series of The Science of Coffee—and this time we’re diving even deeper into coffee’s hidden microscopic secrets! Over the past year, narrative audio producer and coffee professional James Harper has scoured academic journals, ventured deep into coffee farms, and conducted bold tasting experiments. Now, he’s weaving those discoveries into captivating audio stories that r...
Freshness and Grinding, Part 2: How grinders work deep inside 06.05.2024 47:23
Deep inside your coffee grinder, tiny changes can have massive consequences. This episode takes you deep inside Mahlkönig’s grinders to show you how coffee is ground and the importance of particle sizes on flavour. If you’re a home coffee lover, you could easily spend thousands of dollars on your coffee grinder. But after diving deep into the R&D of grinder manufacturing, I learned that afte...
Freshness and Grinding, Part 1: Protecting your coffee’s flavours 22.04.2024 49:41
For your coffee to taste its best, it’s crucial you buy fresh roasts and grind fresh.… .….Or maybe not. When I began creating this episode, I was convinced that ‘fresh is best’. But, after delving into the science of coffee freshness, I don’t believe that anymore. This episode goes deep into how diffusion and oxidation changes a coffee’s flavours. You’ll learn what it takes to store your coffee...
What Is Good Science? Part 2: How to think like a scientist 08.04.2024 55:14
In the last episode, I discovered that rinsing my Chemex filter papers was a waste of time! As a result I’ve managed to claw back over seven days of my life left on earth. But why stop there? The coffee industry is full of elaborate ways of brewing and savouring coffee: fancy drippers, cold metal balls, “slurp-able” cupping spoons. These are very fun, but how many of them actually affect the fla...
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