How Does Coffee Grind Size Affect Flow Rate? What Are the Differences Between Various Filter Dripper Brands and Filter Papers?

A few days ago, we mentioned the importance of extraction time. Extraction time is the total time used for hot water to extract coffee, and the duration determines how much substance is extracted by the hot water, making extraction time extremely important. What determines extraction time is the infiltration speed of hot water. When the infiltration speed of hot water is faster, extraction time becomes shorter, and vice versa.

Many friends might think that the grind size of coffee powder is the only way to control flow rate. But this is not the case - grind size is just one of the factors that controls flow rate. Besides grind size, there are other factors that can affect the flow rate! Want to know more? Of course you do! Then listen as FrontStreet Coffee explains it step by step.

1. The Impact of Grind Size

Although many may have heard this repeatedly, for the benefit of beginners, FrontStreet Coffee will explain again how grind size affects flow rate! Extraction time is measured as the total time it takes for the target amount of water to pass through the coffee bed! With other factors unchanged, for the same coffee beans, the coarser the grind used, the faster the water flow rate during extraction; the finer the grind, the slower the water flow rate!

This is because the finer the grind, the smaller the gaps between coffee particles, leaving less space for hot water to flow, so it can only flow slowly, and vice versa. However, this only applies to the same coffee beans. Different coffee beans will have completely different flow rates at the same grind size due to differences in roast level and processing method. FrontStreet Coffee has mentioned this before, and interested friends can check previous articles for more information~

2. The Impact of Equipment

Besides the subject of extraction (coffee powder), the equipment used for extraction can also change the flow rate! The primary piece of equipment in this regard is the dripper!

There are many different drippers on the market, and different drippers have various designs in terms of shape and structure! The flow ribs and drainage holes of the dripper will change the seepage speed of coffee liquid, which is the flow rate. When a dripper has more, longer, and more prominent ribs, there is more space for water to seep through, which can speed up the flow rate - the V60 is a perfect example! The reverse is also true. The same applies to holes: when a dripper has more and larger holes, there are more places for coffee liquid to seep through, thus changing the flow rate. Besides drippers, filter paper is also a significant factor affecting flow rate. Different materials and shapes of filter paper will naturally have completely different flow rates. However, it's important to know that besides material and appearance differences affecting flow rate, filter papers of the same shape and model can also have completely different flow rates.

They say the difference between filter papers is as great as that between humans and chimpanzees, and there's good reason for this! Even for the same model 01 virgin wood pulp conical filter paper, Hario and Kono will have completely different flow rates despite having the same appearance due to different manufacturing processes (Hario conical filter paper has a faster flow rate, while Kono conical filter paper has a slower flow rate).

3. Human Factors

The height and flow rate of our water injection will cause different degrees of agitation in the coffee bed! The greater the water flow, the stronger the agitation, and vice versa. Agitation means using hot water to stir the coffee powder, allowing flavor compounds to dissolve more quickly.

When we use water flow with strong agitation capacity, the water will carry the fine particles that have absorbed water on the surface to the bottom of the dripper. We all know that fine particles can block the filter paper holes due to their small size. If these fine coffee particles happen to block the filter paper holes at the bottom, the space for liquid flow will be reduced, thereby slowing down the infiltration speed. Therefore, we can see that besides grind size, there are many other factors that affect water flow rate, which is extraction time. When grind size is limited and cannot be adjusted, to change the flow rate, why not try adjusting from other aspects~

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