Paper filters have a reputation for giving your coffee cup a cleaner, more vibrant taste compared to filters made of other materials, such as fabric and metal.
But with a wide range of paper filters on the market, varying in size, shape and thickness, it can be difficult to choose the best one for your preparation device.
To find out more, I spoke with two winners of the filtered coffee championship: 2018 Indonesian champion Hiro Lesmana and two-time Romanian champion Gabriel Carol. Read on to find out what they said.
You may also be interested in our article on how the shape of the Filter coffee can influence the taste of coffee
What should you look for in your paper filter?
According to Hiro and Gabriel, people often don’t think enough about which paper filter to use when preparing pour-over coffee. Understanding how and what materials are used in their manufacture, and how their composition affects extraction can provide information for the preparation process.
But first, let’s take a step back and see exactly what we want from our coffee filters.
The basic function of a filter is simple: during extraction, it must separate the coffee from the brew water, in order to produce a clean tasting filtered coffee with little or no sediment.
In addition to this, the same quality of paper filters can also vary significantly. The different levels of thickness and porosity modify the efficiency with which the paper extracts the aromas and oils from the ground coffee, ultimately altering the mouthfeel and the flavors experienced in the cup.
To start, consider what your paper filter is made of. Various raw materials are used to make paper filters, from mineral fiber pulps and plant fibers to soft and hard woods.
The length of the fiber usually determines the porosity of the filter paper, which then affects the compounds and oils that are extracted in the final cup.
Bamboo and abaca (also known as Manila hemp) have the longest fibers of all the common raw materials used to make paper filters and are therefore more porous (thus more oils reach the cup). In contrast, eucalyptus pulp has the shortest fibers and is the least porous of all the pulps used to make paper filters.
Lastly, you will have to think about the size and shape of the paper filter. Capacity and compatibility with the preparation device are the two most important factors. Each filter can hold a different amount of water and coffee grounds, and each will conform to a specific shape (like a flat-bottomed or tapered drip cone, for example).
Flat or tapered bottom?
Making sure that it fits your brewing device should be a priority when choosing a filter. There are two main styles of pour over coffee making devices: conical and flat bottom. Each has its own unique characteristics that influence extraction.
Hario V60 and Chemex are two of the most popular tapered devices today, while Kalita Wave and Fellow Stagg X are fairly common flat bottom devices. Each of them uses a paper filter with its corresponding shape.
Cone-shaped devices tend to draw faster, which, according to Gabriel, makes aromas more vibrant and acidities more “juicy.” In contrast, he argues that flat-bottomed devices tend to extract coffee more slowly, making it more full-bodied.
According to research by SCA and UC Davis, with respect to extracted flavors and aromas, there are substantial differences in the cup profile offered by flat-bottomed and conical devices.
This study from SCA and UC Davis explains that the differences in shape between the two devices influence the flow of water throughout the extraction. Changing the flow rate alters what scientists call “mass transfer”, that is, the speed at which water moves through the coffee.
The study revealed that for lighter roasts, flat-bottomed devices produced more sweet and floral notes, while those with a conical shape added slightly heavier and berry flavors.
In the case of the darker roasts, the flat-bottom drip devices gave the cup more chocolate, woody and nutty notes. In contrast, cone-shaped devices enhanced bitterness.