Causes of Fast Pour-Over Coffee Flow Rate and Solutions: What to Do When Anaerobic Coffee Beans Drain Too Quickly

The Fast Flow Rate of Anaerobic Coffee Beans

Many friends have asked FrontStreet Coffee, "Why is the extraction time normal when brewing other coffee beans, but when brewing anaerobic coffee beans, the flow rate is extremely fast, often finishing in less than a minute and a half?"

If you usually use a hand grinder to grind beans, you should have noticed that when grinding ordinary light-roasted washed or natural processed beans, it requires significant effort, while grinding anaerobic coffee beans of similar roast levels allows you to turn the grinder smoothly and effortlessly.

This is because anaerobic processed coffee beans have a looser and more brittle texture. They absorb water and release gases very easily, so during blooming, the coffee powder layer of anaerobic processed beans easily swells into a large "hamburger" shape.

With smooth gas release during blooming, the loose-textured, low-density coffee powder produces more foam during brewing. Additionally, during the initial water pour, the coffee powder tends to float on the surface and cling to the edges of the filter cup. The bed's water resistance becomes smaller, making water flow more easily, so it's rare to encounter clogging issues when brewing anaerobic processed coffee.

Understanding the Flow Rate Issue

If the flow rate when brewing anaerobic processed coffee beans is unusually fast—for example, if other coffee beans have an extraction time of about 2 minutes, but anaerobic beans finish in less than 1 minute and 30 seconds—then the flow rate is unreasonably fast.

This issue lies in the grind size. When brewing coffee, people typically only use 2-3 grind settings—one for light roast beans, one for dark roast beans, and at most, one additional setting for medium roast beans. They then categorize grind settings based on the bean's roast level.

Anaerobic beans with rich floral and fruity acidity are naturally categorized under the light roast setting. However, in reality, the particle size ground at the same setting is coarser than ordinary light roast coffee. FrontStreet Coffee has verified this using a #20 sieve. FrontStreet Coffee used the EK-43s grinder at setting 10 to grind African, American, and Asian washed coffee beans respectively, and the pass rate measured with a #20 sieve was 80% (±2%).

When using setting 10 to grind anaerobic coffee beans, the pass rate with a #20 sieve was between 73-75%. This means that ground at the same setting, the particles are coarser than those of regular coffee beans, so water flow naturally becomes faster. To achieve the same fineness with an 80% pass rate on a #20 sieve, the grind setting needs to be adjusted to 9.2-9.5.

Solutions and Brewing Tips

Therefore, if you find that the flow rate when brewing coffee is much faster than usual, you need to adjust your grinder to a finer setting. (Some suggest that brewing anaerobic beans requires a finer grind setting—this statement is not entirely accurate. It's the grinder's setting that needs to be adjusted finer, while the actual particle size should be the same as that used for daily brewing of washed and natural processed coffee beans.)

Of course, if you want a more sufficient extraction time, you can use a smaller water flow during pouring without lifting the powder bed too high. This way, the brewed coffee flavor will be richer and more full-bodied.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473