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 genesis of the SCA’s Water Quality Handbook, and where we are today understanding the impact of minerals on our water.

I strongly recommend listening to the two episodes before this one first: Getting great water for coffee, step-by-step & The two ingredients in water that ruin your coffee, and the ancient story behind them

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Want to go deeper into water chemistry?

Read the SCA’s Water Quality Handbook BWT White Paper on the effects of magnesium (German) Christopher Hendon’s Instagram where he’ll announce his new version of his book, Water for Coffee Do an online Certificate of Advanced Studies at the Coffee Excellence Centre

Season 3 of The Science of Coffee is made possible by these leading coffee organisations:

The Coffee Quest | BWT | TODDY | Algrano | Probat

Note: this is a reworked version of my 2022 episode Water for Brewing Coffee, including portions of my 2024 episode How to think like a scientist, part 2.

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 critters ruin your coffees today.

This story will help you remember the two invisible ingredients in your water that have a huge impact on coffee flavour and your brewing equipment: calcium and hydrogen carbonate.

Read Marcia Bjonerud’s amazing book, Reading the Rocks

Please spread the word about The Science of Coffee! Leave a 5 star rating on Spotify Follow me on Instagram and tag me in an Instagram story Write a review on Apple Podcasts

Discover how I make these Filter Stories episodes by subscribing to my Substack newsletter

Season 3 of The Science of Coffee is made possible by these leading coffee organisations:

The Coffee Quest | BWT | TODDY | Algrano | Probat

Note: this is a reworked version of my 2022 episode Water for Brewing Coffee.

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 concepts matter for coffee flavour and equipment

• How to test your water at home

• How to fix it, depending on what you’re working with

These aren’t one of my usual narrative episodes—they’re a straightforward, practical guide to help you take control of your water.

By the end of these episodes, you’ll be able to say: “I know what good water for coffee is and how to get it”.

I hope it helps you as much as it helped Lucia.

Check my website for all the visuals mentioned in this episode, including:

SCA graph for excellent water (the “map”)

Map of different water hardness across Paris

My Berlin water report

The nightmarish table of conversions…

Results from my water tests in my Berlin studio

Bottled water brands rated for their hardness and alkalinity

Please spread the word about The Science of Coffee! Leave a 5 star rating on Spotify Follow me on Instagram and tag me in an Instagram story Write a review on Apple Podcasts

Discover how I make these Filter Stories episodes by subscribing to my Substack newsletter

Resources mentioned in the episode:

SCA’s Water Quality Handbook

Hardness and alkalinity dripper testing kit (also good for keeping your fishies happy)

BWT Penguin Filter Jug (what I used to use with the magnesium cartridges)

BWT BestAqua ROC (what now I use)

BWT BestBarista (for cafes)

Create your own water by adding minerals to very soft or distilled water: JoJo Hersh’s simple calculator using epsom salts and bicarbonate of soda, and Barista Hustle’s more elaborate one.

Want to go deeper into water chemistry?

BWT White Paper on the effects of magnesium (German) Christopher Hendon’s book Water for Coffee Do an online Certificate of Advanced Studies at the Coffee Excellence Centre

Read The Craft and Science of Coffee Barista Hustle's Water course Some water content on YouTube by James Hoffman and Lance Hedrick

Season 3 of The Science of Coffee is made possible by these leading coffee organisations:

The Coffee Quest | BWT | TODDY | Algrano | Probat