Batch filter

A certified batch brewer holds the bed between 92 and 96 °C for the whole cycle and finishes in six minutes. Most cheap machines fail the first test, which is why their output tastes flat regardless of the coffee.

What a certified brewer actually guarantees

Two things, and they are the two that cheap machines miss: the water reaches the bed between 92 and 96 °C and stays there, and the whole cycle finishes inside six minutes. A machine that dribbles lukewarm water for ten minutes under extracts the first half of the bed and over extracts the last, in the same pot.

The basket shape is not decoration

A flat basket holds a shallow bed and needs a medium grind; a cone holds a deep one and wants it slightly finer. Filling a twelve cup basket with four cups of coffee gives a bed too thin to hold the water back, which is why half batches taste weaker than the ratio says they should.

Ratio, and the scoop problem

Sixty grams of coffee per litre, which is nearly double what the scoop supplied with most machines suggests. Weigh it once and mark the level on the basket if you do not want to weigh it daily. Most disappointing machine coffee is a dosing problem wearing a machine costume.

The hotplate is the enemy

Coffee held on a hotplate cooks. Twenty minutes is enough to turn a decent brew bitter and flat. Brew into an insulated carafe, or brew what you will drink in the next half hour.