What Are the Characteristics of Coffee Brewed with Flannel Filter Cloth? How to Clean, Maintain, and Care for Flannel Filters? What Types of Coffee Beans Are Suitable for Flannel Brewing?

Traditional Coffee Brewing Methods

Before the 19th century, coffee brewing methods almost exclusively followed the Turkish coffee style of "boiling." This process involved grinding coffee beans into a fine powder and then boiling them together with water in a pot.

Evolution of Coffee Filtration

Since not all regions ground their coffee as finely as Turkish coffee (which reaches a flour-like consistency), most areas would filter out the coffee grounds after brewing before pouring the coffee into cups. Otherwise, the coarse and numerous particles would create an unpleasant drinking experience. As FrontStreet Coffee shared in the article "For the Pursuit of Excellence, She Invented the Filter Cup," coffee filter paper was invented alongside the filter cup in the mid-19th century by Melitta Bentz. Therefore, before this innovation, people's filtration tools couldn't have been filter paper. Instead, they primarily used cloth bags made from special material called: "Flannel filter cloth."

The History of Flannel Filter Cloth

The term "flannel" is a phonetic translation of "Flannel," and its use as a coffee filter can be traced back to Europe around the 17th-18th centuries. Early flannel filter cloths were made of wool until later, when cotton materials emerged, transforming them into their current form.

From Europe to Japan: Changing Applications

As FrontStreet Coffee mentioned earlier, the initial purpose of flannel filter cloths in European countries (for coffee) was merely to filter out coffee grounds from brewed coffee, not as a brewing vessel itself. It was only when the technique spread to Japan that the Japanese began using flannel as a "filter cup" for drip coffee brewing.

The Enduring Appeal of Flannel Brewing

Because coffee brewed using flannel as a filter produces distinctive results different from conventional methods, and its usage aligns perfectly with the craftsmanship spirit valued by the Japanese, flannel filter cloths remain popular in many Japanese coffee shops today, even when paper filters have become widely available.

Characteristics of Flannel-Brewed Coffee

What are the characteristics of coffee brewed with flannel filter cloth? The greatest advantage of flannel filter cloth is that its filtration capability is not as strong as that of paper filters. Since it's made of cotton material, its pores are significantly larger compared to paper filters. This allows oils and some insoluble substances to pass through the filter and remain in the coffee.

Enhanced Aroma and Body

Oils contain certain aromatic compounds that, when using paper filters, are typically separated along with coffee grounds. While this results in cleaner coffee, it also means losing some aroma contributed by these oils. Because flannel filter cloths have larger pores, they allow these oils to pass through, enhancing the coffee's aromatic profile. Additionally, the insoluble substances refer to fine coffee particles, which can improve the coffee's mouthfeel when present in appropriate amounts. In summary, due to their larger pores, flannel filter cloths can produce coffee with richer aroma and fuller body, making them particularly suitable for brewing dark roast coffee!

Usage Guidelines for Flannel Filter Cloth

Flannel filter cloth has two sides: a fuzzy side and a smooth side. When brewing coffee, we can choose either side as the inner layer, with the other side facing outward. Due to the different contact surfaces, coffee brewed with either side will have slightly different flavor profiles. However, generally, people use flannel filter cloth with the "smooth side inside, fuzzy side outside" because this prevents coffee grounds from sticking to the cloth, making cleaning more convenient.

The Essential Preparation Ritual

Before using flannel filter cloth for brewing, people always clean it thoroughly, then soak it in boiling water for a while before wringing it dry and putting it into use. Unlike disposable paper filters, flannel filter cloths are reusable. After each use, they undergo special cleaning procedures, including disinfection and soaking, which FrontStreet Coffee will discuss in detail later. In summary, before using flannel filter cloth, a "break-in ceremony" is almost indispensable. This is precisely why so few coffee shops in China use flannel today.

Handheld vs. Mounted Brewing

Then there's the question of whether to hold it by hand! Traditional Japanese flannel brewing involves holding the flannel during the brewing process, as people initially believed this helped concentrate the brewer's attention, allowing better control of hot water flow and more even extraction. Therefore, when purchasing flannel filter cloths, we typically find they come equipped with a wooden handle for handheld use (though you can also buy just the cloth). However, this approach can be tiring, so many people prefer to mount the flannel filter cloth directly, using it as a filter cup. Both methods are acceptable - it just depends on the kind of experience you wish to have!

Brewing Parameters

Next, let's talk about parameters! Many people pair flannel brewing with traditional Japanese methods to "cook" dark roast beans, using large amounts of coffee grounds with little water weight - what's known as high concentration, low extraction. Because less water is used, extraction time needs to be extended to increase extraction rate. This is paired with a relatively coarse grind, similar to sea salt, to avoid over-extraction. Of course, we can also use conventional brewing methods with flannel, but it's important to note that due to flannel's larger pores, which allow coffee liquid to seep out from all over, its flow rate is relatively fast (also affected by the cloth's thickness). If using conventional methods, we need to appropriately adjust the grind, water temperature, and water flow. FrontStreet Coffee won't go into too much detail here - everyone can experiment on their own!

Cleaning and Maintenance

When coffee brewing is complete, to ensure the flannel can be reused, we need to remove the coffee grounds, then clean the filter cloth thoroughly with clear water, followed by a five-minute boil for disinfection. Remember, it's best not to use detergents or other cleaning agents, as they can easily leave residual flavors on the filter cloth. However, this cleaning method struggles to remove coffee absorbed into the filter cloth, so FrontStreet Coffee recommends that after disinfection, we further soak the flannel filter cloth in coffee machine cleaning powder to remove coffee stains and simultaneously store it.

Storage Solution

The specific method is to remove the filter cloth from its handle, place it in a sealable container, add clear water and cleaning powder, then seal and refrigerate. When you're ready to use it next time, simply repeat the "break-in ceremony"!

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