How to Brew Coffee with a Flat-Bottom Dripper? Characteristics of Pour-Over Coffee with Flat-Bottom Filters

Understanding Even Extraction in Pour-Over Coffee

Even extraction is crucial for pour-over coffee brewing. Whether considering equipment or technique, we strive to achieve uniform extraction of coffee grounds. When FrontStreet Coffee discusses why most people now use conical drippers, one reason is for better water distribution to achieve even extraction.

The flat-bottom dripper, which appeared slightly later than conical drippers, also claims to provide even coffee extraction. So how effective is it?

The Origins of Flat-Bottom Drippers

The first company to design a flat-bottom dripper was Kalita, the same company that popularized wedge-shaped drippers. After the V60 became immensely popular, they likely needed to introduce a more competitive dripper. In 2010, Kalita launched the Wave series, which featured this flat-bottom, round dripper. Because the special filter paper used resembles the shape of a paper cup cake, this style of dripper is also known as a "cake dripper." (However, considering the naming of the Wave series and its unified appearance, it was more likely positioned to compete with the competitor's Cloud series.)

Regardless, the Kalita Wave dripper pioneered the flat-bottom dripper category, followed by other brands like B and Blue Bottle who introduced their own flat-bottom drippers.

How Flat-Bottom Drippers Achieve Even Extraction

FrontStreet Coffee will first explain how drippers help achieve even extraction of coffee grounds. Regarding even extraction, FrontStreet Coffee must reiterate that no method can guarantee every single coffee particle extracts the same amount of substances. Therefore, the "even extraction" mentioned here is not absolute uniformity, but rather a relative comparison. For example, when FrontStreet Coffee previously discussed the V60 dripper, we compared it with wedge-shaped drippers. From a top-down perspective, the circular opening of the V60 makes it easier to achieve even water distribution, resulting in more even extraction compared to drippers that struggle with uniform water flow.

Flat-bottom drippers also maintain the circular opening, making them comparable to conical drippers in terms of even water distribution. The advantage lies in the coffee bed thickness. When we shift our perspective to the side, conical drippers have a pointed bottom with gradually expanding surface area upward, resulting in a thicker coffee bed with inconsistent thickness across different points – thickest at the center and thinnest at the edges. This can lead to significant differences in extraction rates between upper and lower coffee grounds. Due to their flat bottoms, flat-bottom drippers create a thinner and more uniform coffee bed with the same amount of coffee. Thus, with even water distribution, extraction throughout the coffee bed becomes much more uniform.

Flavor Profiles: Conical vs. Flat-Bottom

Under normal circumstances, conical drippers led by the V60 produce coffee with rich aromas, emphasizing sweet and sour fruity notes with distinct layers. Flat-bottom drippers focus on balanced mouthfeel and highlighting sweetness.

Design Variations in Flat-Bottom Drippers

Of course, even among flat-bottom drippers, design differences affect the final flavor expression. FrontStreet Coffee will explain this from two aspects: bottom design and rib design of the dripper body. Flat-bottom dripper bottoms typically feature drainage holes and "paper supports." The drainage holes in flat-bottom drippers use multiple small holes, and drainage speed depends on the distribution and total area of these holes. Larger total hole area results in faster drainage, such as recently introduced hollow-bottom designs, which essentially provide large drainage areas.

Besides drainage holes, the bottom also features raised frameworks to support the filter paper. If the bottom were smooth and the filter paper completely adhered to the dripper bottom, water would struggle to flow down. Conversely, allowing some space between the filter paper and dripper maintains smooth drainage speed.

The rib design of the dripper body falls into two categories: water-retaining and water-channeling. For example, the horizontally distributed circular ribs of the Wave dripper serve to slow down water flow and maintain a level water surface. The ring-shaped structure allows water at higher points to flow along the ring to lower positions on the other side, demonstrating a balancing effect.

The other type features vertical ribs similar to conical drippers, serving to guide and channel water flow, preventing blockages and accumulation during extraction.

However, the rib effect in flat-bottom drippers is less significant than in conical drippers. FrontStreet Coffee mentioned in our article about filter paper fit that only where the filter paper contacts the dripper do the ribs demonstrate their effect. Since flat-bottom drippers use cake-style filter paper that only adheres to the dripper along the folded edges, the ribs only function in those specific areas.

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