Stop Following Recipes: Why I Wrote a Book on the Science of Coffee Brewing

The same beans, the same grinder, the same recipe — bright and sweet on Monday, flat and sour on Thursday. If that has ever happened to you, this new book is for you.

Here is a story you have probably lived. You watch a video by a champion barista, or you buy a bag of beans with a recipe printed on the side. You copy it exactly — the same dose, the same water, the same grind number, the same pours, timed to the second. And the cup is… disappointing. Thin, or sour, or bitter, or just flat. So you find another recipe and try again. And again. You build a collection of other people’s numbers, and you still cannot reliably make the cup you want.

The problem is not you, and it is not the recipe. The problem is that a recipe is a set of numbers that only worked for one particular bean, on one particular grinder, with one particular water, in one particular pair of hands. Change any of those, and the numbers no longer point at the same cup. A grind setting of “20” means nothing on a different grinder. “94°C” does different things to a dense light roast than to a porous dark one.

That is why I wrote Stop Following Recipes: The Science of Coffee Brewing. Over the next six weeks I’ll be sharing a post twice a week that walks through the ideas in the book, chapter by chapter. This first post is the map: what the book is, why brewing is simpler than the mysticism makes it sound, and the two ideas that everything else hangs on.

A Curiosity That Refused to Let Go

Why a designer ended up writing about brewing chemistry

I never set out to become a coffee professional. My background is in design — a Master’s from Hong Kong Polytechnic University and years spent building digital products. No family in the industry, no early exposure. Just a curiosity that started, as it does for many people, at the brewer, with that same maddening question: why did the same setup give me two completely different cups on two different days?

Chasing that question pulled me from casual brewing into serious study — pulling apart every variable, tasting obsessively, studying under SCA programmes, and earning a Q Instructor certification from CQI. I founded Tasse Coffee Education in 2019 and opened our Tokyo roastery in 2023. I wrote this book because I got tired of watching curious, capable people give up on great coffee, convinced that brewing was a mysterious art reserved for baristas with magic hands. It isn’t. It’s chemistry and physics you can understand and steer.

The First Big Idea

Extraction is a timeline, not a switch

Strip away the mysticism and what happens in your brewer is simple to state: hot water is dissolving compounds out of a porous solid. Everything you taste — every bright acid, every note of caramel, every harsh edge of bitterness, every ounce of body — is a molecule that either did or did not make it out of the coffee and into your cup.

The key insight is that these compounds do not all leave the bean at once. Small, fast ones come out first (the acids and salts that taste sour and sharp); medium ones next (the sugars and browning products that taste sweet and round); and large, slow ones last (the phenolics that taste bitter and build body). Sour, sweet, and bitter are not three separate flavours you add — they are positions on one timeline.

The Second Big Idea

Every cup sits on two independent axes

The second idea is what turns tasting into troubleshooting. One axis is how far you extracted, which runs from sour to bitter. The other is how strong you made it, which runs from watery to intense. They are independent — you can have a strong-but-sour cup or a weak-but-bitter one — which is why “it tastes bad” is never enough. You have to ask which axis is off.

Once you can place a cup on those two axes, fixing it stops being guesswork and becomes a matter of pulling the right lever in the right direction. Grind and time slide you sideways along extraction; your brew ratio slides you up and down in strength. Everything else in the book — all the chemistry, all twenty-six variables, all the brewing methods — is ultimately about steering those two things.

Who This Book Is For

Anyone tired of collecting other people’s numbers

If you own a grinder, a dripper, and a scale, and you are tired of copying recipes that only sometimes work, this book is written for you. It does not tell you to “trust your palate” and leave you there — your palate is the goal, not the method. It gives you the mechanism behind every taste, so that when your cup is wrong, you know why, and you know exactly what to change. No lab required; just a willingness to understand what your gear is actually doing.

Written by Wing Yuen — SCA Authorised Trainer, CQI Q Instructor, and founder of Tasse Coffee Education & Roastery in Shinjuku, Tokyo. Wing roasts daily, brews daily, and teaches the science of coffee to students across Hong Kong and Japan.