Here’s a problem that’s bothered me long before I owned a roaster. Every time someone talks about fermentation in coffee — washed, natural, wild, inoculated — they’re comparing different coffees. Different farms, different varieties, different altitudes, different years. So when the cups taste different, what actually caused it? You can’t say. Too many variables moving at once.
This kit fixes that. One lot of coffee from a single farm in Antigua, Guatemala, split four ways and processed with four different fermentations. Same genetics, same soil, same harvest, same everything — except the one variable we’re actually interested in. It’s the cleanest experiment in coffee you’ll ever taste, and you get to be the one running it.
What’s in the box
The four coffees
Four 80g bags, each a different process, whole bean. I’ve deliberately left the tasting notes off — and I won’t tell you which bag is which. The entire point is to taste them blind, side by side, and trust your own palate. Brew them the same way, line them up, and pay attention.
No fermentation at all. The mucilage is stripped off by machine, so nothing microbial happens. This is your baseline — the pure expression of the bean’s genetics and the ground it grew in. Everything else gets measured against this cup.
48 hours submerged with a selected Saccharomyces yeast — the wine and bread yeast. Yeast works differently from bacteria: expect it to push the body, the sweetness, and the aromatic complexity in its own direction.
48 hours submerged, this time with a deliberately chosen Lactobacillus culture — the same bacteria family behind yoghurt and sourdough. Watch what a bacterial ferment does to the acidity and brightness against your control.
48 hours submerged, fermented by whatever microbes were already living on the coffee and around the farm. This is the traditional method most of the world’s coffee goes through — nobody’s steering it, the local population just does its thing.
A controlled experiment you can drink
I came to coffee sideways, through physics and then medicine — two fields where the scientific method rules. Change one thing, hold everything else fixed, and watch what happens. That’s the only honest way to know what causes what.
Coffee almost never gives you that. This kit does. It’s the rare chance to taste a variable in isolation, and it’s exactly the kind of thing I started Copperopolis to share. No mysticism, no marketing fog — just one coffee, four honest processes, and your own senses doing the measuring.
The people behind it
Who made this possible
Lucia Solis — Fermentation Consultant
Lucia studied viticulture and enology at UC Davis, specialising in microbiology and fermentation science, then spent nine years making wine in Napa Valley before turning to coffee in 2014. She’s since worked alongside producers in more than fifteen countries.
She designed the four processes in this kit. Her work is about treating processing as a strategic tool — reproducible, stable, and grounded in the real economics of a farm, not spectacle for its own sake.
James Hoffmann — Expert Slurper, Coffee Guru Extraordinaire and Project Lead
An award-winning coffee professional, author and communicator, James won the World Barista Championship in 2007 and has become one of the industry’s most recognised voices through his books and educational YouTube channel.
He leads the project and will host the live global tasting — the moment thousands of us around the world brew these same four coffees together.
Caravela — Origin & Distribution Partner
Caravela has worked in Guatemala since 2016, building long-term relationships with coffee-growing communities through on-the-ground buying stations and a year-round team — direct engagement, quality control, and real traceability.
For this project they handle the green sourcing, processing oversight and global logistics, moving these coffees from the wet mill in Antigua to roasteries like mine around the world.
Copperopolis is one of a small number of roasters worldwide taking part — I’m roasting these in small batches here in Killay, on the edge of the Gower peninsula.
Choose your kit
Three ways in
The Kit
- 4 × 80g, the four ferments
- Whole bean, blind
- Printed tasting & scoring card
- Everything you need for the live cupping
The Kit + Spoon
- Everything in The Kit
- Engraved Copperopolis cupping spoon
- The proper tool for slurping & scoring
- Yours to keep
The Full Experiment
- Everything in Kit + Spoon
- Plus a full 227g bag of Kenya Murue AA (whole bean)
- (It’s a £10 bag for just £5 more)
The global tasting
Saturday 3rd October, 3pm UK
The whole point is to do this together. On 3rd October at 3pm UK time, James Hoffmann hosts a live global cupping on YouTube — thousands of people around the world tasting these exact four coffees at the same moment. Brew your set at home and join in, or run your own comparison any time before or after. I’ll send everything you need to take part.
Whole bean only — you’ll want a grinder
This one’s whole bean across the board, and there’s a reason. To taste four processes fairly you need to grind fresh and grind identically across the four. Pre-ground would lose some of the more volatile aromatics that we’re going to taste.
The coffee
Farm: Finca San Miguel Urias
Producers: Hector & Lilian Leal
Region: Antigua Valley, Guatemala
Altitude: 1460–1540 masl
Varieties: Caturra, H1, a little Bourbon
Processes: Mechanically Demucilaged / Wild / Lactobacillus / Yeast
Format: 4 × 80g, whole bean only
Roast: Light–medium, to keep roast character out of the way of the comparison
Pre-order & dispatch
This is a limited pre-order tied to the tasting date. Orders will be roasted for shipping from 14th September. Anything else you order alongside it will ship at the same time as your kit. Numbers are capped — once they’re gone, they’re gone.
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