Introduction to Starbucks Coffee Bean Grinding Degree, Grind Coarseness Values, and Grinding Scale

Many coffee enthusiasts have purchased Starbucks coffee beans, only to find themselves unsure about the appropriate grind size when they return home. They stare at the settings on their grinder, worried that grinding too coarsely or too finely might result in an unpleasant cup of coffee, so they come to ask FrontStreet Coffee how to determine the right grind.

When FrontStreet Coffee explains pour-over coffee, they always mention several important factors that affect coffee extraction or flavor, including water temperature, grind size, and coffee-to-water ratio. Among these, the grind size determines the size and uniformity of coffee particles, which directly affects the efficiency of water extraction of flavor compounds from the coffee grounds. So in daily brewing, how should we determine the appropriate grind size for different coffee beans? In this article, FrontStreet Coffee will explain how to adjust the grind size for pour-over coffee.

The Impact of Grind Size on Coffee Extraction

FrontStreet Coffee has demonstrated through different brewing experiments that the finer the grind, the more easily coffee particles accumulate on the filter paper, creating greater extraction resistance. This results in slower flow rate and longer extraction time. The extraction rate of coffee substances is higher, producing a more intense brew; similarly, the coarser the grind, the larger the gaps between particles, with fewer coffee particles in contact with hot water. Extraction resistance is weaker, coffee drips faster, and the extraction rate is lower, resulting in a milder flavor. So what are the characteristics of grinding coffee beans too finely versus too coarsely during the brewing process?

What Happens When Pour-Over Coffee is Ground Too Finely?

From the appearance of the coffee particles, when ground too finely, the particles are smaller, and because of their reduced size, the spacing between particles is shorter, making it more difficult for water to pass through. This results in a longer drip time during the brewing process. The finer grind leads to smaller particles that create a paste-like consistency when moistened and filtered. After brewing, the coffee bed makes it difficult to see individual particles, with predominantly paste-like characteristics.

What Happens When Pour-Over Coffee is Ground Too Coarsely?

From the appearance of the coffee particles, when ground too coarsely, the particles are larger, and because of their increased size, the spacing between particles is greater, making it easier for water to pass through the coffee grounds. This results in a shorter filtration time during the brewing process. The coarser grind leads to larger particles, and after brewing, the individual coffee particles in the coffee bed are clearly visible. The bed struggles to form a complete, uniform structure and may have gaps or fractures.

The Impact of Grind Size on Coffee Extraction

The grind size not only determines the size and shape of coffee particles after grinding but also affects the surface area. The finer the coffee is ground, the larger the surface area, increasing the contact area between water and coffee, which allows for extraction of more substances. The increased surface area also provides more outlets for carbon dioxide to escape from within the coffee beans.

How to Adjust the Grind Size for Pour-Over Coffee

When grinding coffee daily, even seemingly uniform coffee grounds have maximum and minimum particle sizes that differ by at least 0.6mm. Generally, we refer to coffee particles larger than 0.85mm as coarse particles, while those smaller than 0.25mm are called very fine particles. If these two types of particles account for more than 40% of your total coffee grounds, they are not suitable for pour-over coffee. Confused? Don't worry! FrontStreet Coffee recommends purchasing a 0.85mm aperture test sieve.

How to Use a Sieve to Determine Coffee Grind Size?

Weigh 10g of coffee beans, grind them with an approximate grind setting, then pour the grounds into the sieve for screening. Weigh the sieved coffee grounds (make sure to sieve until no more coffee grounds can pass through). A pass-through rate of 75%-80% (7.5-8g from 10g of grounds) is the most suitable grind size for light to medium roast coffee beans, while a pass-through rate of 65%-70% (6.5-7.0g from 10g of grounds) is most suitable for medium to dark roast. If the pass-through rate exceeds the appropriate range, adjust to a coarser grind; if it doesn't reach the appropriate range, adjust to a finer grind.

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