Muddy French press coffee comes from the plunge, not the press
Pushing the filter down quickly drives the fine particles straight through the mesh and into the cup, where they keep extracting and turn bitter. The device is not the problem. The last ten seconds are.
The French press has a reputation for producing sediment, and it is a reputation it half deserves. A mesh screen cannot hold back the smallest particles, so a press will always give a heavier, more textured cup than a paper filter does. That is the point of it.
What is not inevitable is the silt at the bottom of the mug and the bitterness that arrives with it. That comes from how the coffee is made, and most of it from a single movement.
What happens when you plunge fast
Pushing the plunger down quickly does not filter the coffee. It pressurizes it. The liquid has to go somewhere, and it goes up around and through the mesh at speed, carrying the finest particles with it — the ones a slow press would have left below the screen.
Those particles do not sit quietly in your cup. They have enormous surface area relative to their size, so they carry on extracting in the mug, all the way through the first several minutes of drinking. That is the bitterness people blame on the beans.
The five steps
- Grind coarse, like coarse sea salt. This matters most of all. Fine grounds in a press are fine grounds in your mouth, and four minutes of immersion will over-extract them besides.
- Four minutes, lid on, no stirring after the first gentle turn. Pour the water, give it one slow stir to wet everything, put the lid on with the plunger up, and leave it alone.
- Skim. At four minutes, a thick raft of foam and floating grounds sits on the surface. Lift it off with a spoon and discard it. Pressing the plunger through that raft pushes the whole of it into the coffee.
- Press slowly. Ten full seconds, top to bottom. If you feel resistance building, stop, lift slightly, and continue. There should be no effort in it.
- Pour all of it out immediately. Every cup, into mugs or into a separate carafe.
That last step is where most households lose it. A press is not a carafe. Coffee left standing on the grounds keeps brewing, and the second cup poured out of a press twenty minutes later is a different and much harsher drink than the first one was.
On the ratio
Immersion brewing is less forgiving of a weak ratio than drip is, because there is no concentration happening as the water passes through. Use more coffee than feels reasonable: one part coffee to sixteen parts water, by weight, is the number worth memorizing. A 34-ounce press takes roughly 60 grams of coffee, which is a good deal more than the four tablespoons most of us were taught.
If that sounds like a lot, weigh it once and taste it before deciding. Thin coffee is the single most common complaint about home brewing, and the most common cause of it is measuring by habit.
Cleaning
A press accumulates oil in the mesh and around the screw threads of the filter assembly, where it goes rancid and taints everything afterwards. Once a week, unscrew the plunger assembly entirely, wash the three or four parts separately with soap, and let them dry before putting them back together.
It takes four minutes and it is the cheapest improvement available to anybody who already owns the equipment.