Introduction:Grind size is one of the key factors that determine the flavor direction in pour over coffee. Different levels of grind coarseness directly affect water flow rate, extraction efficiency, and the final mouthfeel of the coffee. This article will explore, from a practical brewing perspective, how grind size alters extraction parameters and coffee flavors, and provide a standard grind reference suitable for pour over, helping you dial in your ideal cup.
In the process of making pour over coffee, water temperature, grind coarseness, and brew ratio are the three core elements that influence extraction results. Among them, the degree of coffee grinding directly affects particle size and distribution uniformity, thereby altering the speed at which water penetrates the coffee bed and the efficiency of flavor extraction. Simply put, the finer the grind, the more tightly packed the coffee particles become, increasing resistance to water flow, lengthening extraction time, and often extracting more substances—resulting in a richer coffee flavor but also potentially more bitterness and astringency. Conversely, a coarser grind allows water to pass through more smoothly, shortens extraction time, and leads to a lighter, thinner flavor profile.
To better understand the actual impact of grind size on extraction, you can adjust grind coarseness as the sole variable and compare using the same coffee beans. For example, using Honduran Lishan beans, perform pour overs at fine, medium, and coarse grind sizes, then analyze the differences in performance under each grind setting based on measured coffee concentration and extraction yield.
When using a finer grind, the coffee particles are smaller, packed more densely, with less space between them, making it harder for water to penetrate and thus extending drip time. At this point, the coffee bed often becomes sludgy and it’s hard to distinguish individual particles. Fine grinding increases the total surface area of the coffee, allowing water to contact more soluble material, which raises both concentration and extraction yield. The coffee tends to taste intense, with bitterness and astringency more likely to be amplified, while subtle flavors may be masked.
On the other hand, using a coarser grind results in larger coffee particles, with more space between them, allowing water to pass through more quickly, thus significantly shortening extraction time. With a coarse grind, the coffee bed is more loosely packed and may even fail to form a fully even coffee bed, sometimes resulting in channeling. Due to the reduced surface area in contact with water, fewer soluble substances are extracted, leading to lower coffee concentration, an overall lighter flavor, less distinct layers, a light body, but potentially lacking depth.
Comprehensive test data shows that when using a finer grind, concentration is about 1.32%, with an extraction yield of 19.53%; medium grind yields a concentration of 1.17% and an extraction yield of 17.28%; while coarse grind coffee has a concentration of only 0.84%, with the extraction yield dropping to 12.37%. It is clear that slight adjustments in grind size have a significant impact on both extraction yield and the final flavor expression of the coffee.
For pour over coffee, the recommended grind size is approximately 80% passing through an 0.85mm sieve, which usually achieves a more balanced extraction result. Of course, adjustments can be made according to bean roast level, origin characteristics, and personal preference during actual brewing.
Choosing the right grinder and burr type is equally important. Grinders on the market can generally be divided into three main types: conical burr, flat burr, and flat steel (ghost teeth), each differing significantly in grinding principles and the shape of the resulting coffee particles.
Conical burr grinders crush coffee beans into blocky particles through a pressing mechanism, and this type of burr is commonly found in hand grinders. Because of the “pressing” principle, although the particles are relatively uniform, fine particles are more likely to be produced during the grinding process. However, the coffee grounds produced by conical burrs are more three-dimensional, absorb water more slowly, release fewer substances in the early stages of brewing, so the rise in concentration is limited—but over longer extraction times, they are also less likely to release excessive off-flavors or astringency. They are a common choice for pour over coffee. It should be noted that there is a significant difference in grinding fineness and stability between high-end and low-end conical burr grinders.
Flat burr grinders cut coffee beans by rotating upper and lower parallel burrs, producing particles that are mostly flaky or strip-shaped. Because coffee beans are more prone to being compressed as they enter the grinding zone, more fine particles are generated. However, the flaky particles can release aroma and soluble substances more quickly, helping improve extraction efficiency and initial flavor expression. Although more fine particles are produced, with proper control, excessive off-flavors can still be avoided, making them suitable for both pour over and espresso grinding needs.
Ghost teeth (flat steel) grinders can grind coffee beans into particles close to spherical in shape, with relatively small differences in particle size. Although they produce slightly more fine particles, the overall distribution is more consistent. This grinding method is better suited for achieving a balanced flavor and delicate mouthfeel in pour over coffee, especially enhancing the expression of subtle fruit acidity and sweetness.
Practical pour over recommendations are as follows: 15 grams of coffee, a brew ratio of 1:16, with water temperature controlled at 90°C. The first step is to pour 30 grams of water for a 30-second bloom, followed by the second pour of 210 grams of water. The total brew time is recommended to be between 1 minute 50 seconds and 2 minutes, which helps achieve a balanced extraction.
The above content is compiled by CoffeeHunters, a coffee news website.
