Impact of Pour-Over Coffee Flow Rate on Flavor! Pour-Over Coffee Watering Techniques! What is the Pour-Over Coffee Brewing Ratio?

A delicious cup of pour-over coffee doesn't just depend on the right combination of parameters, but also significantly tests the brewer's observation of the coffee bed and control of water flow. Therefore, the use of different water flow rates is often a concern for many friends. For example, when should you use a large water flow, and when should you use a small water flow... FrontStreet Coffee has shared many articles addressing this issue.

Even so, FrontStreet Coffee found that many friends and even well-known bloggers still have some confusion about the definition of water flow size, believing that a large water flow means using a larger water column to stir the coffee grounds more forcefully, while a small water flow means using less water to reduce stirring of the coffee bed. Although the size of water flow does have some impact on the degree of stirring, the effect is actually not significant. In fact, what determines the strength of water flow's stirring effect on the coffee bed is our pouring height and our circular speed. What does water flow size really determine? At the same height and same circular speed, water flow size determines "the contact time between water and coffee grounds." To help everyone see this more clearly, FrontStreet Coffee will now conduct a comparative experiment to see what the real impact of large and small water flows on coffee extraction actually is~

How Large is Large Flow? How Small is Small Flow?

Almost forgot! Before starting the experiment, FrontStreet Coffee will first share how water flow size is classified! Large and small water flows actually refer to the amount of water you pour from the kettle in the same amount of time, which is the water flow rate. Because different manufacturers' pour-over kettles have different constructions, there are no clear numerical standards for large and small water flows. However, we can understand it this way: a small water flow refers to the smaller vertical water column poured by your current pour-over kettle, while a large water flow is the opposite.

Generally, the small water flow rate of a coffee kettle will be in the range of 2ml to 4ml of hot water per second, while a large water flow will be in the range of 6ml to 8ml per second, depending on the structure of the kettle you're using and how much water it contains. For example, the Hario Cloud Kettle used by FrontStreet Coffee needs a minimum flow rate of 2.3ml/s to maintain a vertical water column, with a maximum of 8ml/s. If you exceed these two values, the water column cannot remain vertical (as shown in the image above)! So now we'll use these two values as standards for our brewing experiment!

Brewing Experiment

The coffee beans used in this experiment are: Ethiopian Chaka, a bean that FrontStreet Coffee has been quite fond of recently. Under conventional brewing (using a combination of large and small water flows), this bean exhibits high sweetness similar to fruit candy, with refreshing flavors like berries and lemon. All parameters except water flow are identical in this experiment: same pouring height, same circular speed, only differing in water flow size, to see what differences the brewed coffee will have! The extraction parameters are as follows: 15g coffee grounds, grind: Ek43 setting 10, coffee-to-water ratio 1:15, brewing method: three-stage pour, filter: V60, water temperature: 92°C.

First, we pour twice the amount of coffee grounds (30ml) for a 30-second bloom to release carbon dioxide from the coffee beans, allowing for better extraction by subsequent hot water!

After the bloom ends, we pour the second stage of 120ml of hot water in large circles using our respective water flow settings. When the water has mostly permeated through, we follow the same pattern to pour the final 75ml of hot water, but this time in small circles. Then we wait for the drip to finish, remove the filter cone, and complete the brewing.

The coffee brewed entirely with small water flow took 2 minutes and 8 seconds, about 8 seconds slower than conventional brewing (which normally takes about 2 minutes). However, its coffee performance was not inferior at all. Although the flavors weren't as pronounced as conventional brewing, and the layers were relatively less rich, it was much mellow in mouthfeel, with a silky, cream-like texture.

Meanwhile, the coffee brewed entirely with large water flow took 1 minute and 50 seconds, about 10 seconds faster than conventional brewing. Its flavor performance was somewhat inferior. Although it also exhibited lemon and berry flavors, the sweetness wasn't as high, and the mouthfeel was thin. Concentration measurements also verified the perception that it was weaker than the others (lower than other brewing methods).

So we can know that with completely identical height and circular speed, water flow size primarily affects the drainage speed, in other words, the contact time between water and coffee grounds. The reason many bloggers find that coffee brewed with large water flow tastes stronger than with small water flow is because when they use large water flow, they also pair it with a rather "bold" circular pouring motion, while when using small water flow, they pour very gently. This creates higher extraction rates with large water flow and lower stirring intensity with small water flow. When brewing coffee, we need to adjust the water flow according to the state of the coffee bed, so water flow control is very important. For detailed instructions on practicing pouring, we can refer to the article "How to Practice Water Flow Control," so FrontStreet Coffee won't elaborate further here~

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