Pour-Over Coffee Grind Size Standard Units and Scale Settings Single-Serve Coffee Ground Dosage

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Brew beginners often come to FrontStreet Coffee to ask how to determine the grind size for each coffee bean, how grind size affects coffee extraction, and how to distinguish the fineness of coffee grounds at home. In this article, FrontStreet Coffee will discuss grind size for pour-over coffee.

The Impact of Grind Size on Coffee

Grinding is crucial for coffee. The size of coffee particles directly affects the efficiency of hot water wetting and extracting the coffee. Theoretically, the more uniform the coffee particles, the more consistent the overall extraction efficiency, resulting in better coffee flavor. Concentration and extraction rate decrease as the grind becomes coarser and increase as the grind becomes finer. The degree of grinding refers to the size and shape of the coffee after grinding, as well as the surface area. The finer the coffee grounds, the larger the surface area, and the increased contact area between water flow and coffee allows for more extraction. Increased surface area (coarser grind) also provides more places for carbon dioxide inside the coffee beans to escape.

Roasting's Effect on Coffee Bean Aroma and Carbon Dioxide Production

Roasting brings out the full aroma of coffee. The Maillard reaction refers to a series of degradation and polymerization reactions between monosaccharide carbohydrates and amino acids, which occurs throughout the entire roasting process. Monosaccharides and amino acids react at different temperatures to produce many complex aromas - nut, almond, cream, and chocolate aromas come from the Maillard reaction. Caramelization is the oxidation and browning reaction of sugars during heating, producing honey, maple, and caramel aromas. Simply put, the longer the roasting time, the more acidic substances are released from the coffee beans. For medium roasts, lighter roasted coffee has more pronounced acidity like citrus and berry flavors. Darker roasted coffee has more prominent caramelized flavors like cocoa, caramel, and nuts.

In addition to creating aroma, roasting also produces carbon dioxide inside the coffee beans. The darker the roast, the more carbon dioxide is produced. To ensure better carbon dioxide release during brewing, FrontStreet Coffee recommends resting coffee beans when purchasing freshly roasted ones. Resting allows coffee beans to release carbon dioxide through the one-way valve on the packaging without opening it, helping aromatic substances and oils merge and bringing all aromatic substances inside the beans to an easily extractable state. FrontStreet Coffee recommends resting medium-light roasted coffee beans for 3-4 days from the roast date, and medium-dark roasted coffee beans for 5-6 days from the roast date.

How to Determine Coffee Bean Grind Size?

Using FrontStreet Coffee's freshly roasted coffee beans as an example, pour-over single-origin coffee beans are divided into medium-light and medium-dark roasts.

FrontStreet Coffee's medium-light roasted coffee beans: Medium-light roasted coffee beans will exhibit acidity, while caramelized substances are not easily extracted. Frontsteet recommends using medium-fine grind size (80% pass rate through a #20 sieve with 0.85mm mesh, i.e., fine sugar size). Medium-fine grind can slow down water flow through the coffee bed, better extracting acidic substances, sweet substances, and caramelized substances to balance coffee flavor expression. Medium-fine ground coffee is recommended to be brewed at 90-91°C water temperature. Too high water temperature will over-extract caramelized substances, producing bitterness; too low water temperature will under-extract, only extracting some acidic and sweet substances, making the coffee taste bland and boring.

FrontStreet Coffee's medium-dark roasted coffee beans: Medium-dark roasted coffee beans generally have low acidity with prominent body, meaning caramelized substances will be more abundant. Frontsteet recommends using medium-coarse grind size (70% pass rate through a #20 sieve with 0.85mm mesh, i.e., coarse sugar size). Medium-coarse grind can speed up water flow through the coffee bed, preventing caramelized substances from being over-extracted, allowing coffee flavor and mouthfeel to be sweet and rich without producing unpleasant bitterness. Medium-coarse ground coffee is recommended to be brewed at 88-89°C water temperature. Too high water temperature will make coffee bitter and hard to swallow; too low water temperature will make coffee taste bland and boring.

How to Use a 0.85mm #20 Sieve?

Regarding grind size, Frontsteet determines it through the sieving method, following SCA (Specialty Coffee Association) recommendations for pour-over coffee grind size, combined with practical operational verification. If you don't have a sieve at home, FrontStreet Coffee suggests observing water flow speed to judge - too fast flow means grounds are too coarse, too slow flow means grounds are too fine.

First, prepare 10g of coffee beans for grinding. Initially determine a grind size based on fine sugar and coarse sugar sizes, then pour into the sieve, cover it, and shake left and right to let coffee grounds pass through the sieve into the collection tray below. Continue until no more coffee grounds pass through the sieve. Then prepare an electronic scale and container, zero them, pour the sieved coffee grounds into the container and weigh. If 8g±0.1g passes through, it's medium-fine grind; if 7g±0.1g passes through, it's medium-coarse grind. If the pass rate is too high, adjust the grind coarser; if the pass rate is too low, adjust the grind finer.

The Importance of Grind Uniformity

Ground particles should be uniform. After coffee beans are ground, they become powder, and the distribution of particle sizes has a great relationship with the quality of the coffee beverage. The more concentrated the particle size within the target range, the more uniform the grind, and the better the flavor. If there are too many coarse particles, the deep flavors hidden inside the coffee won't be extracted; if there are too many fine particles, the coffee will taste too complex and bitter. If serious uneven grinding occurs, Frontsteet recommends changing the grinding equipment.

Several important factors that affect coffee extraction or flavor are water temperature, grinding, and coffee-to-water ratio. Among these, the degree of grinding determines the particle size and uniformity of coffee grounds, directly affecting the efficiency of water flow extracting flavor substances from the coffee grounds. In this article, Frontsteet explores how much impact coffee grind size has on a cup of coffee and shares internal calibration data for grind size!

The finer the coffee is ground, the more easily the coffee grounds accumulate on the filter paper, creating greater extraction resistance, resulting in slower flow rate and longer extraction time. The extraction rate of substances in coffee is higher, and the brewed coffee is more intense.

Similarly, the coarser the coffee is ground, the larger the gaps in the coffee bed, with less coffee grounds in contact with hot water, weaker extraction resistance, faster coffee dripping speed, lower extraction rate, so the coffee flavor is also lighter.

Therefore, simply changing the grind degree can create huge differences in coffee taste, which is why coffee grinding is so important.

Let's use grind size as a variable to brew coffee, brewing three groups of coffee with fine, medium, and coarse grinds respectively, using Honduras Lychee Orchid coffee beans. After brewing, we measured coffee concentration and calculated extraction rates respectively to verify the above points.

Brewing Protocol

Coffee amount: 15 grams

Brewing ratio: 1:16

Water temperature: 90 degrees Celsius

Brewing Process

Frontsteet uses segmented extraction. The bloom water amount is twice the coffee grounds, i.e., 30g of water for 30 seconds bloom. Small flow circular pouring to 150g, then when the water level drops and is about to expose the coffee bed, continue pouring to 240g and stop. Total extraction time is 2 minutes.

Results Comparison:

Fine Grind

Concentration: 1.32%

Extraction rate: 19.53%

Medium Grind

Concentration: 1.17%

Extraction rate: 17.28%

Coarse Grind

Concentration: 0.84%

Extraction rate: 12.37%

What Happens When Coffee Is Ground Too Fine?

From the appearance of particles, the size is smaller, and because the particles are smaller, the spacing between particles is shorter, making it more difficult for water to pass through, so the dripping time during brewing is longer.

Fine grinding results in smaller particles. After coffee grounds get wet and filtered, they present a paste-like state. The brewed coffee bed makes it difficult to see all coffee particles, with mostly muddy conditions.

Fine grinding results in smaller coffee ground particles, increasing the surface area of coffee particles, providing more places where water flow can extract coffee substances, so concentration and extraction rate increase. The coffee tastes intense, with obvious bitterness and astringency, while other flavors are masked.

What Happens When Coffee Is Ground Too Coarse?

From the appearance of particles, the size is larger, and because the particles are larger, the spacing between particles is greater, making it easier for water to pass through the coffee grounds, so the filtering time during brewing is shorter.

Coarse grinding results in obvious coffee particles in the brewed coffee bed, with difficulty forming a complete coffee bed and gaps.

Coarse grinding results in larger coffee ground particles, reducing the surface area of coffee particles, providing fewer places where water flow can extract coffee substances, so concentration and extraction rate also decrease. The coffee tastes bland and flavorless, with light mouthfeel and almost no flavor.

How to Determine the Correct Pour-Over Grind Size?

Therefore, grinding is one of the crucial steps in coffee extraction. An appropriate grind coarseness is very key to brewing a delicious cup of coffee. But what exactly is the appropriate degree of coarseness? FrontStreet Coffee recommends using a 0.85mm sieve (i.e., national standard #20) as a benchmark, with a grind degree where about 80% of coffee grounds pass through the sieve being recommended as the pour-over coffee grind degree.

Of course, for coffee beans with different roasting degrees, the corresponding grind sizes used are also different. For example, Frontsteet uses a grind with 85% pass rate through a 0.85mm mesh sieve for light roast coffee. Medium roast coffee uses a grind with 75% pass rate through a 0.85mm mesh sieve. Dark roast coffee uses a grind with 67% pass rate through a 0.85mm mesh sieve. These data are for reference only.

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