Astringency is the drying, rough, puckering sensation of strong tea or an unripe banana. It is tactile rather than a taste.
What causes it
Over-extraction. The last compounds to leave the grounds include polyphenols that bind to proteins in saliva, which is what produces the dry feeling.
Unripe or under-developed beans. Green, immature coffee is astringent no matter how it is brewed. So is under-developed roasting.
Very fine grind with long contact. The classic combination.
Distinguishing it from bitterness
Bitterness is a taste at the back of the tongue. Astringency is a feeling across the whole mouth, like the tongue has been dried out.
They usually appear together, but astringency alone points at the beans rather than the brew.
The fixes
Grind coarser. First and most effective. Shorten contact time. Lower the temperature by two or three degrees. Widen the ratio slightly — 1:2.2 rather than 1:2 for espresso.
In espresso specifically
Astringency at a normal shot time usually means channelling — some of the bed is being blasted while the rest is barely touched, and the blasted part is severely over-extracted.
Use WDT and check the tamp is level.
If nothing works
Try a different bag. Some coffee is astringent from the farm, and no amount of dialling fixes green fruit.
Last reviewed 8 August 2026