Fines Migration and Filter Stalling: Why Your Pour-Over Drawdown Chokes
A pour-over can begin normally and then slow to a drip. Coffee brewers often call this “stalling” or “choking.” One major cause is fines migration: tiny particles travel through the slurry and collect against the paper, restricting flow.
Where fines come from
Every grinder produces a distribution of particle sizes. Brittle dark roasts, some dense light roasts, misaligned burrs, and aggressive grinding can increase the fine fraction. The goal is not literally zero fines; it is a distribution that suits the brewer and recipe.
Why agitation matters
Heavy stirring, repeated swirling, and high turbulent pours keep fines moving. They can settle at the filter wall or bottom and form a low-permeability layer. Often described as a “muddy bed.”
How to reduce stalling
- Grind a little coarser.
- Use fewer, gentler pours.
- Keep kettle height controlled to limit turbulence.
- Swirl only enough to level the bed.
- Rinse the paper fully and avoid pressing it into blocked ribs.
Do not chase drawdown alone
A slow brew can still taste good, and a fast brew can be hollow. Use time as a diagnostic alongside taste. If the cup is drying and harsh with an unusually long drawdown, fines migration is a strong suspect.
A grinder known for a consistent flat-burr workflow, such as the Turin DF64 Gen 2, gives you a stable baseline for testing pour structure and agitation.
