Pros and Cons of Center Pouring Method in Pour-Over Coffee: Analysis of Water Distribution and Circular Movements

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Advantages of Circular Pouring

In the article "The Science of Water Pouring," FrontStreet Coffee mentioned that circular pouring has obvious advantages compared to center pouring. Especially in terms of stability and uniform extraction, center pouring simply cannot compete.

Center vs. Circular Pouring Experiment

This time, let's switch to the perspective of center pouring. If this method truly had no merits, it should only be found in historical records by now. In fact, quite a few people still use this method to brew coffee! Let's conduct a comparative experiment using FrontStreet Coffee's Guo Ding Ding coffee beans as an example, comparing center pouring with circular pouring. Given that in the previous comparison, the water flow of center pouring was at a slight angle, which created turbulence, this time we'll use a small water flow to prevent any angle in the water stream.

Both pouring methods this time use single-pour technique, with circular pouring still during the bloom stage. After confirming that the coffee bed state was not problematic, we tested the concentration of both cups of coffee. The results showed that center pouring had a concentration of 1.23%, while circular pouring had a concentration of 1.10%.

In other words, with a small water flow, the extraction rate of center pouring is actually higher than that of circular pouring. FrontStreet Coffee found two possible reasons for this result.

Temperature Factor

The first reason is temperature. Although everyone's kettle temperature is the same, the water temperature participating in extraction within the coffee grounds may not be the same. If you've noticed FrontStreet Coffee's previous article "What's the Difference Between High and Low Water Columns When Brewing Coffee," you'd know that high water columns lose more heat due to greater contact with air, resulting in lower extraction rates compared to low water columns. This situation is quite similar - stationary pouring contacts less cold air than circular pouring, thus retaining more heat.

Coffee Grounds Distribution

The second reason is that center pouring contacts more coffee grounds. When we brew coffee now, we mostly still use conical drippers. These drippers have a characteristic: wide at the top and narrow at the bottom, with thick coffee grounds in the middle and thin coffee grounds around the edges.

From a top view, circular pouring does achieve "uniform watering," but this may not necessarily be the case from a side view.

With center pouring, the thickest middle layer of coffee grounds gets fully extracted, and the water also has a diffusion effect, spreading to the surrounding areas to supplement the thinner layers of coffee grounds around the edges. This way, less water sneaks away, and more substances are extracted from the coffee.

In the same experiment, after FrontStreet Coffee finished testing the data, we tasted the coffee. FrontStreet Coffee found that the flavor profile of center-poured coffee was more concentrated and had bitter tastes. In contrast, circular pouring was quite gentle and pleasant. It seems that the extraction rate calculated from concentration testing only represents overall extraction. In reality, center pouring caused uneven extraction with high extraction rates in the center and low rates around the edges - one high and one low averaged out to the overall extraction rate that FrontStreet Coffee measured.

Three-Stage Pouring Comparison

Next, let's look at the differences between three-stage center pouring and circular pouring. The parameters are basically the same as above, just changing from single-pour to three-stage pouring. The measured concentration was 1.32% for center pouring and 1.45% for circular pouring.

In this round of comparative experiments, it was actually the small-flow circular pouring that had a higher extraction rate. This is because the coffee bed height was lower than with single-pour, and the pouring time was extended, meaning the scouring effect of the water column was more significant in the later stages. Additionally, thanks to the water level not rising too high, less water escaped from the edges.

Optimal Pouring Technique

Therefore, from these experiments, it's easy to explore and derive a pouring method that combines circular and center pouring. A more mainstream brewing logic is to use three-stage extraction: first, pour normally during the bloom stage; second, use circular pouring for uniform penetration; third, use small circular pouring to ensure extraction while reducing turbulence; and fourth, use center pouring to suppress extraction and avoid undesirable flavors.

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