How to Change One Brewing Variable at a Time
Here's a mistake I made for years: I'd tweak grind, ratio, and temperature all at once, then wonder why the cup changed — with no idea which move did it. Change one thing, hold the rest steady, and compare. That's the whole trick.
The loop
- Record a baseline brew (dose, water, ratio, grind, temperature, time, taste).
- Pick one variable to adjust.
- Brew again with only that change.
- Compare the two brews side by side.
Where to keep the records
Use the Brew Log: duplicate your last brew, change a single field, and use Compare to see exactly what differed.
Where this comes from
I didn't invent single-variable testing — it's just the basic scientific method applied to coffee. I lean on it because it's the only way I've found to actually learn what changed the cup. Editorial habit, not a cited study.