Definition
Extraction is the process by which water dissolves and carries away soluble compounds from ground coffee. In pour-over brewing, this occurs as water passes through a bed of coffee grounds, dissolving material along the way.
Extraction is typically expressed as a percentage: the ratio of dissolved coffee solids to the dry mass of the coffee grounds used. An extraction of 20% means that 20% of the coffee's mass has been dissolved into the water.
Key Insight
Extraction percentage is independent of strength. A light-bodied cup can have high extraction, and a strong cup can have low extraction. These are separate dimensions.
Mechanism
Extraction occurs in stages. Different compounds dissolve at different rates:
- •Early extraction (0-10%): Acids and light aromatics dissolve quickly. These compounds contribute brightness and fruity notes.
- •Mid extraction (10-20%): Sugars and balanced aromatics. This range typically produces sweetness and complexity.
- •Late extraction (20%+): Bitter compounds and heavier phenols. These add body but can overwhelm at high concentrations.
The goal in pour-over is typically to extract primarily from the first two stages while minimizing contribution from the third.
Measurement
Extraction percentage is calculated using total dissolved solids (TDS) and brew ratio:
Extraction % = (Brewed Coffee Mass × TDS) ÷ Dry Coffee Mass
Example: 300g brewed coffee at 1.35% TDS from 20g dry coffee = 20.25% extraction
TDS is measured using a refractometer, which provides a precise quantification of dissolved solids.
Practical Note: Most home brewers do not have access to measurement tools like a refractometer. Extraction can instead be evaluated by taste, which is ultimately the most important measure of success. Key sensory indicators include:
- •Underextracted coffee: sour, thin, or hollow flavors
- •Well-extracted coffee: balanced sweetness, clarity, and complexity
- •Overextracted coffee: bitterness, dryness, or heavy astringency
By adjusting grind size, pour technique, brew ratio, or temperature and tasting the result, brewers can iteratively reach a preferred extraction without technical instruments. Taste is the reference point that ties all brewing variables together.
Optimal Range
The Specialty Coffee Association suggests an optimal extraction range of 18-22% for filter coffee. This is a guideline, not a rule.
In practice:
- •Light roasts may taste best at 20-22%
- •Medium roasts often prefer 19-21%
- •Darker roasts can be optimal at 18-20%
These ranges overlap significantly. Roast level, processing method, and personal preference all affect the ideal extraction point.