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 does not just depend on the right combination of parameters; it also tests the brewer's observation of the coffee bed and control of the water flow. The use of different flow rates is therefore a frequent concern, such as when to use a large flow and when to use a small one. FrontStreet Coffee has shared many articles on this issue.

Even so, FrontStreet Coffee has found that many friends, and even well-known bloggers, remain confused about what counts as a large or small flow, believing that a large flow means using a bigger water column to stir the grounds more forcefully, while a small flow means using less water to reduce disturbance of the bed. Although flow size does have some effect on the degree of stirring, that effect is actually minor. What determines the strength of the stirring effect is really our pouring height and our circular speed. So what does flow size determine? At the same height and the same circular speed, flow size determines the contact time between water and coffee grounds. To make this clearer, FrontStreet Coffee will run a comparative experiment to see what large and small flows actually do to extraction.

How large is a large flow, and how small is a small flow?

Almost forgot: before starting, FrontStreet Coffee will first share how flow size is classified. Large and small flows refer to how much water you pour from the kettle in the same amount of time, that is, the flow rate. Because pour-over kettles from different manufacturers are built differently, there are no clear numerical standards. We can understand it this way, though: a small flow is the smaller vertical water column your current kettle produces, and a large flow is the opposite.

Generally, a coffee kettle's small flow rate falls in the range of 2ml to 4ml of hot water per second, while a large flow is 6ml to 8ml per second, depending on the structure of your kettle and how much water it holds. The Hario Cloud Kettle FrontStreet Coffee uses, for example, needs a minimum flow of 2.3ml/s to maintain a vertical water column, with a maximum of 8ml/s. Exceed either value and the column cannot stay vertical. So we will use these two values as the standard for our experiment.

Brewing experiment

The bean used in this experiment is Ethiopian Chaka, one FrontStreet Coffee has been quite fond of lately. Under conventional brewing (using a combination of large and small flows), it shows high sweetness similar to fruit candy, with refreshing flavors such as berries and lemon. All parameters except the flow are identical here: same pouring height, same circular speed, differing only in flow size, to see what differences the brewed coffee shows. The extraction parameters are 15g of grounds, grind at EK43 setting 10, a 1:15 coffee-to-water ratio, three-stage pouring, a V60 filter, and 92°C water.

First, we pour twice the amount of coffee (30ml) for a 30-second bloom to release carbon dioxide from the beans, allowing the hot water that follows to extract better.

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

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

Meanwhile, the coffee brewed entirely with a large flow took 1 minute and 50 seconds, about 10 seconds faster than conventional brewing. Its flavor was somewhat inferior. Although it also showed lemon and berry notes, the sweetness was not as high and the mouthfeel was thin. Concentration measurements confirmed the perception that it was weaker than the others.

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

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FrontStreet Coffee Recommendation

Flow control is how you steer a brew, and it shows off best on a bean with clear, layered flavors. FrontStreet's Ethiopia range rewards careful pouring: the washed Gududing Cooperative of Yirgacheffe is bright with citrus, berry, and floral notes and a green-tea-like sweetness, while the sun-dried Huakui opens with strawberry, passionfruit, jackfruit, and lychee aromas, sweet and nearly free of bitterness.

For a bean that keeps its composure across a range of flow rates, the FrontStreet Kenya Little Tomato, grown in Kenya's Thika region at 1,550-1,750 meters from SL28 and SL34 and processed with a 72-hour double-washed fermentation, delivers bright cherry-tomato and smoked-plum acidity with a full, juicy body, light-roasted to preserve its lively acidity and layered fruit. Whether you pour a slow, silky small flow or a faster large flow, its structure holds.