How to Choose and Adjust Coffee Grind Size 1 to 10? Understanding Grind Coarseness for Light and Dark Roast Coffee Beans

Introduction

Anyone who has used a manual grinder to grind coffee beans can deeply relate to the experience - some coffee beans grind effortlessly, while others require tremendous effort to grind. Similar phenomena occur with electric grinders, where some beans finish grinding with a quick "whir~" sound, while others take much longer.

What Causes This Phenomenon?

Many people's first reaction is that it's related to the density of coffee beans. Higher density beans are harder and thus more difficult to grind, while lower density beans are softer and relatively easier to grind.

The density of coffee beans is determined during their growth. Coffee grown at higher altitudes experiences lower temperatures, which slows down the coffee's growth rate, allowing more substances to accumulate in the seeds (coffee beans). This means the mass density of the coffee beans is higher. This is also why some coffee-producing countries in Central America use altitude hardness to classify coffee grades (for example, in Costa Rica, coffee grown above 1400 meters is classified as SHB - Strictly Hard Bean).

In other words, grinding Ethiopian coffee beans from 2000 meters above sea level would be more difficult than grinding Brazilian coffee beans from an average of 1000 meters. However, while density does affect the ease of coffee grinding, it's not the primary factor. There's another factor called "brittleness."

Brittleness

Brittleness is the opposite of toughness, referring to the tendency to fracture under external forces such as tension and compression. For example, if you place a raw coffee bean, a lightly roasted coffee bean, and a dark roasted coffee bean on a table and press them with your fingers, you'll find that the raw bean and lightly roasted bean are very difficult to break, while the dark roasted bean crushes easily. This is brittleness.

This is related to the degree of roasting. The entire coffee roasting process is a dehydration process. The longer the roasting time, the more moisture evaporates from the coffee, making its internal structure more porous. Of course, the roasting level will be deeper, making it easier to grind and break apart.

How Does Brittleness Affect Grinding?

We know that dark roasted coffee beans are easier to grind, while light roasted coffee beans are more challenging. Let's observe the microscopic world of coffee grinding. When coffee is ground, it experiences compression force between the two burrs and cutting force as the burrs rotate. When using the same grinder setting, dark roasted beans are more easily crushed. The median particle size of dark roast coffee will be smaller than that of light roast coffee, meaning at the same grinder setting, the overall particle size of dark roast will be finer than that of light roast.

How Does This Knowledge Help With Brewing?

1. Grinder Settings Are Not Absolute

Due to differences in bean brittleness, even when using the same grinder setting, the resulting particle size may not be the same. Therefore, we need to check the grind size for each coffee bean. FrontStreet Coffee uses a calibration method with a #20 standard sieve, with an 80% pass rate for hand-pour grinding of light roast coffee beans. However, because substances in dark roast coffee are more easily extracted, dark roast coffee needs to be ground coarser, approximately with a 70% pass rate through a #20 sieve.

Most importantly, it's essential to understand the relationship between your grinder's settings and particle size.

2. Clean Your Grinder More Diligently

Dark roasted coffee beans produce more fine particles, which can easily remain in the burrs. These residual dark roast coffee particles can easily affect the flavor of the next cup of coffee. Therefore, after grinding one type of coffee bean, be sure to clean the fine particles remaining in the burrs. FrontStreet Coffee uses a small amount of the same coffee beans to grind before grinding to "clean the burrs."

Important Notice :

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FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473