The Perfect Shape of Pour-Over Coffee Grounds! Can You Determine Brewing Skills from the Coffee Bed? How Long Should You Bloom Pour-Over Coffee?

Yesterday, a friend shared an interesting observation with FrontStreet Coffee. He noticed that most people, when brewing coffee, will keep their eyes fixed on the changes in the filter cup, even during waiting intervals when no water is being poured, as if trying to glean some information from the coffee bed.

Surprisingly, there's actually quite a bit of information that can be gleaned from the filter cup. For example, the freshness and density of coffee beans, the grind size, the path and method of water pouring, and so much more. All of these can be observed during the brewing process! So today, FrontStreet Coffee wants to share what kinds of information we can read during the coffee brewing process.

1. The Degree of Bulging During Coffee Bed Blooming

Blooming is a preparatory step included in most brewing methods because it helps release large amounts of carbon dioxide from the coffee grounds, allowing the subsequently poured hot water to better dissolve flavor compounds. During the blooming process, the released carbon dioxide forms bubbles when enveloped by water. These bubbles then push the coffee bed upward, creating a mound-like bulge.

The size of the coffee bed's bulge and its water retention ability can help us determine the freshness of the coffee, as both conditions primarily depend on the carbon dioxide content. When there's more carbon dioxide, the bulge in the coffee bed will be larger, and vice versa. Additionally, because bubbles create barriers that slow down water flow, when there's more carbon dioxide, the water retention effect will be stronger, allowing the coffee bed to remain moist for longer. Conversely, when carbon dioxide is insufficient, the coffee bed will quickly dry out. Therefore, we can determine the freshness of coffee beans from the size of the bulge and water retention during blooming, because fresher coffee beans retain more complete carbon dioxide stored during roasting, resulting in relatively larger bulges and better water retention effects.

Dark roasted coffee often produces larger bulges than light roasted coffee because carbon dioxide content is also related to the degree of roasting. The deeper the roast, the more carbon dioxide accumulates in the coffee beans. Additionally, the expansion rate of the beans increases, naturally resulting in relatively larger bulges.

2. Raising the Coffee Bed Height

Raising the coffee bed is a pouring technique commonly used when brewing coffee! This technique specifically involves increasing the water flow rate to make it higher than the drainage rate, thereby raising the water level. The coffee grounds in the filter cup can then rise uniformly with the water level and finally distribute evenly around the filter cup. The advantage of this technique is that it helps us reduce bypass water while allowing hot water to extract the coffee grounds more evenly. (Detailed introductions can be found by searching for relevant articles from previous issues.)

However, not all coffee beds can be raised, as this is related to the quality of the coffee grounds. When coffee beans are lighter roasted or have higher density, the coffee grounds will be too heavy to lift. Therefore, from whether the coffee bed can be raised, we can determine the approximate density of these beans and then find corresponding extraction methods.

For example, when the coffee bed cannot be raised, if we don't want to create too much bypass water that would make the brewed coffee taste bland, it's best to appropriately reduce the water flow, allowing hot water to pass through the coffee ground layer as much as possible to fulfill its extraction duty.

3. Foam Color

During the coffee brewing process, many bubbles will float on the surface of the coffee liquid. These are the bubbles formed by carbon dioxide release that FrontStreet Coffee mentioned earlier. The color of these foam will continuously change throughout the brewing process, from dark brown initially, to golden, then to light yellow, and finally turning whitish. It is precisely from these foam colors that we can read information during brewing.

Because these foam colors primarily come from the coffee grounds, some extremely fine and lightweight coffee particles mix into the foam, coloring it. During our brewing process, the poured hot water will wash these fine particles away from the foam. Without these fine particles, the foam color will gradually fade. Therefore, when we see certain foam colors gradually lightening or even turning whitish, it indicates that our water pouring has concentrated in these areas. In other words, from the foam color, we can see the path of water pouring.

4. Water Flow Rate

Next is the water flow rate. The speed of water flow is affected by many factors, such as density, grind size, filter cup, and various other elements. But typically, the speed of water flow mainly depends on the grind size and coffee bean density. When the water flow rate is faster, it usually means the coffee grounds are coarser, giving hot water more space to flow, thus resulting in faster drainage. Conversely, when the water flow rate is slower, it means the grind is finer or the coffee grounds have higher density. After the coffee grounds settle, the gaps between them are smaller, leaving less space for water to flow, thus reducing the speed.

Another reason for slow water flow is excessive fine particles, which can clog the filter holes, thus slowing down the water flow. However, because too many factors affect water flow speed, this situation usually needs to be combined with the fifth point to reach a conclusion. But everyone should know that we cannot directly determine whether a cup of coffee will taste good based on the speed of water flow alone. Because besides extraction time, many other factors affect coffee extraction. So ultimately, we still need to combine this with taste to decide whether parameters need adjustment.

5. The Shape of the Coffee Ground Crater

Finally, let's talk about the shape of the coffee ground crater! Many beginners pursue a deep and uniform crater after brewing is complete, partly because such deep craters are symmetrical and pleasing to look at, and partly because it's often rumored online that the appearance of such deep craters means the coffee will taste good.

But in reality, the formation of the coffee ground crater has no direct relationship with whether the coffee tastes good or not. It only reflects our water pouring method during the brewing process. For example, the technique of raising the coffee bed can contribute to the formation of deep craters. Besides this, there are many different types of coffee ground craters, and as FrontStreet Coffee mentioned, they reflect different water pouring methods. For example, the appearance of a flat-bottomed crater represents that we didn't use too much water flow during brewing; a layered crater means our water flow was too large or too concentrated on certain edges... Due to the numerous types of coffee ground craters, FrontStreet Coffee won't elaborate on them here. Interested friends can move to this article to learn more: "Complete Guide to Pour-Over Coffee Ground Craters".

So, that concludes this article. If there are any other details worth noting during the brewing process, feel free to leave comments in the comment section and let's discuss together~

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