A delicious cup of coffee is hard-won, because from seed to cup is a very long wait. Even at the final step of extraction, you must ensure that the coffee you use meets brewing standards, because extraction is easy, but have you ever thought about it? Coffee grounds are what extract the flavor compounds, so the water, beans, and equipment used can all affect the flavor presentation of a cup of coffee. Today we're talking about coffee grind size—this isn't simple, because even grinders of the same brand are not completely identical, and these subtle grinding differences are enough to affect the coffee grounds. Coffee grounds aren't like soy milk that can be made just by grinding into powder, which is why grinders have so many scale settings and need fine-tuning to find the right grind size; otherwise, even the best coffee beans are wasted.

　　The Importance of Grinding

　　Grinding involves the extraction of coffee. The finer the grind, the higher the extraction rate; the coarser the grind, the lower the extraction rate. This relates to three factors: contact time, extraction rate, and flow rate. The relationship here is mutually reinforcing—one will inevitably affect another.

　　1. The extraction rate of coffee grounds increases with the increase in surface area of the ground powder.

　　2. An increase in surface area means a finer grind; a decrease in surface area means a coarser grind.

　　3. The finer the coffee grind, the higher the extraction rate, so the contact time is shorter.

　　4. The finer the coffee grind, the slower the water flow and the longer the contact time; the coarser the grind, the faster the water flow and the shorter the contact time.

　　This is easy to understand. Espresso machines use an extremely fine grind, so espresso extraction time is only about 30 seconds; drip coffee uses a medium-fine grind, so contact time is around 2 minutes. But when you want to use a particular coffee brewing device, you need to set the grind size accordingly—coarser or finer. If you use extremely fine grounds to make drip coffee, the water flow will inevitably slow down, the contact time will be longer, and the extraction rate will be higher. Conversely, if you use medium-fine grounds to make espresso, the contact area is small, the water flows quickly, the extraction time is short, and the extraction rate is low. Even if you grind to the coarseness for pour-over coffee, how do you verify whether your grind size is correct? Even a slight deviation will produce a different flavor. Therefore, coffee grind size must be verifiable, so that you can achieve the best possible results in coffee preparation.

It is worth noting that many people mistakenly believe that the same grind setting produces grounds of the same size. In reality, different grinders have certain assembly errors, which can be corrected from time to time. Similarly, you can use a standard sieve to measure the fine particle size in order to choose the appropriate grind size.

FrontStreet Coffee grind coarseness standard sieve pass rates are as follows:

Cold drip > Pour-over Siphon (syphon) 80% > Moka American drip 75-80% >  Cup testing 70-75%  > French press 65-70%

　　Grind Size Selection

　　Because different grind sizes correspond to different brewing devices, adjust the coffee grind size according to the device used. Below are the grinds from finest to coarsest and their corresponding devices.

　　1. Turkish coffee: This is an ultra-fine grind, with a texture like flour—basically the smallest setting on an espresso grinder. The smaller the number, the finer the grind.
 

　　2. Espresso (as shown above): Espresso machines use 9 atmospheres of pressure to extract coffee compounds, and this also requires an extremely fine grind. However, a grind as fine as Turkish would clog the portafilter, preventing water from flowing through and causing excessively long extraction time. Therefore, you need to adjust coarser toward a higher number and test. Typically, the dose for a single or double portafilter on an espresso machine is 8-9g for single and 18-20g for double. Extracting 25-30g of coffee liquid for single and 50-60g for double within 25-30 seconds is the standard.

　　3. AeroPress (as shown below): This is a piston-like extraction device that uses manual pressing to extract coffee. Extraction time is about 2 minutes, but it is an immersion-style extraction, so fine grounds can cause over-extraction. Use the pour-over coarseness and adjust 1 or 1.5 notches coarser,介于 medium-fine leaning fine grind.

　　4. Siphon (as shown below): The siphon uses an open flame to heat boiling water, which rises from the lower chamber to the upper chamber for immersion extraction, with stirring during the process. Fine grinding risks over-extraction, so a medium grind adjustment is needed.

　　5. Pour-over coffee (as shown below): This is currently the most popular brewing method, but there are still many grinding deviations. It is commonly said that you should grind to a coarseness similar to fine granulated sugar, but many people don't realize that even when comparing side by side, there will still be deviations. Pour-over coffee uses a medium-fine grind, with a size similar to fine granulated sugar. SCA recommends a sieve pass rate of 75-80%, which is defined as the standard coarseness for pour-over coffee.

　　6. Moka pot (as shown below): The moka pot is an ancient coffee device that extracts coffee from the upper part by heating water in the bottom to boil. It was previously the main method for making espresso-style coffee. The pressure is about 1.5 bar, so a finer grind is needed, close to espresso grind but slightly coarser.

　　7. Cold brew, cold drip: Both belong to long-duration low-temperature immersion extraction, using ice water to slowly extract the flavor compounds from coffee. The extraction rate of ice water is very low, so long soaking requires a medium-coarse grind. Medium-coarse grinding is easier to filter and won't cause the gaps between grounds to be too fine for water droplets to penetrate; cold brew is also easier to filter out coffee grounds.

　　8. French press (as shown above): The French press is also an immersion extraction, but the difference is that the coffee extracted in a French press remains immersed in the pot the entire time, so long soaking will cause over-extraction, making a coarse grind necessary. The grind size is between coarse, similar to the larger particles of brown sugar.

　　The above are my personal suggestions on coffee grind size, for reference only. When you find problems during actual operation, adjust immediately—don't rigidly stick to a certain grind size. People have different tastes; some like it lighter, some like it stronger—this is very normal. The taste you find just right, others might find too strong or too weak. Don't let uncontrollable factors interfere. The most commonly used pour-over coarseness currently has a sieve for calibration, so friends who need calibration can purchase one. Now it's time for the brewing分享. Let's brew Sidamo Flower Kui with the SCA-defined standard pass rate and see what surprises it brings!

        Taking Front Street Ethiopia natural Flower Kui coffee beans as an example
        Region: Guji Hambela
        Variety: Heirloom
        Altitude: 1800-2000 meters
        Processing method: Natural

        Pour-over parameters

        Dripper: V60 Water temperature: 91°C Grind size: Fine granulated sugar (standard No. 20 sieve pass rate 80%) Water-to-coffee ratio: 1:15 Technique: Three-stage extraction

        Brewing: Bloom with 30g of water for 30s, then slowly pour in a circular motion to 120g for the second stage, and after the water level drops halfway, pour again to 225g and stop brewing. Wait for the coffee liquid to finish dripping, then remove the dripper. Total extraction time is 2:00-2:10s.

      Flavor: Tropical fruit, mango, strawberry, passion fruit, full and round acidity, solid mouthfeel

The above content is compiled by CoffeeHunters, a coffee news website.