# Brew Log (/en/docs/brew-log)



A log is not useful because it is complete. It is useful because every cup leaves one decision behind: **next cup, change one variable**.
Brew the next cup with that change, come back to “what you changed last time, and what happened”, and cause and effect slowly come into focus.

Not sure what to change? Diagnose it in [Fix My Coffee](/docs/fix) first. To practise one variable systematically, run a [Real Lab](/docs/labs) — lab records appear here too.

<BrewLog />