A coffee brewing log: recording dose, water, temperature and time

What it is

A brewing log is a per-cup record of the inputs you control and the observations you make, kept in the same fields every time. The inputs commonly logged are coffee mass in grams; water mass in grams (weighed, because a volume mark on a jug is read less repeatably); water temperature at the moment of pouring, as read from a thermometer or as the kettle's setting, stated as which; grind setting as the number on your grinder, together with the grinder model; the brewing method and device; contact or total brew time in seconds; and the beans, with the name on the bag, the roast date as printed and the days since roast. The observations are the yield in grams where it applies, taste notes in your own words, and who tasted.

Why it matters

Discussions about why a cup tasted different usually involve several variables that changed at once. With a log, a difference between two cups can be traced to the one field that differed, and a cup you liked can be reproduced from numbers instead of memory. The log also makes the limits visible: a grinder setting means nothing without the grinder, and "hot water" is not a temperature.

How to apply

• Fix the field list first; a missing field is recorded as a dash, not filled in later from memory.
• Weigh coffee and water on the same scale and note the scale's resolution once in the header.
• Record what happened, not the plan: the second at which you actually stopped the brew, the mass of water that actually went in.
• Between two brews you intend to compare, change one input and hold the others; log the roast date every time, because the beans are ageing between brews.
• Write the taste notes before looking up the previous brew's numbers, and keep opinion and measurement in separate columns.
• Keep the grinder setting and the grinder model together; new burrs or a different grinder start a new series.

Pitfalls

A kettle setting is not the water temperature at the coffee bed; log it as a setting. Ratios computed from volumes ("one cup") do not compare across households. A bag without a roast date leaves the largest variable unknown; write "unknown" rather than a guess. This is a logging convention, not a brewing recommendation, and it gives no target values.