A Guide To Brewing Filter Coffee

Photo Credit: Jim Kalligas

Over the past few decades, filter coffee has become more and more synonymous with specialty coffee culture. Whether brewed with pour over devices such as the CHEMEX® or a batch brewer, it has been embraced by coffee shops and home coffee consumers alike.

Much like pulling an espresso shot, brewing filter coffee is a precise art, whether you’re at home or in a coffee shop. Brewing just a cup or two, manually or with a batch brewer, requires the user to control and manage a number of essential variables.

To learn more about these variables, I spoke with Dale Harris, the 2017 World Barista Champion and General Manager at Hasbean, a roaster based in Stafford, England. He tells us more about filter coffee and points out a few key parameters to keep an eye on.

Extraction & How To Influence It

When we talk about extraction, we mean the process by which the volatile flavour compounds in coffee granules extract into the brewing water. This is how coffee is brewed, whether you’re pulling an espresso shot, plunging your French press, or making filter coffee. And achieving even extraction is important: under-extracted coffee tastes sour and thin, while over-extracted coffee tastes bitter.

Generally, with filter coffee, consumers look for a flavour profile which balances a coffee’s sweetness and body against acidity and clarity in the cup. While selecting good-quality beans is always a great first step, there are a number of complex factors that influence extraction.

Coffee To Water Ratio

Finding the right balance between the amount of water you use and your coffee grounds is crucial. Shifting the balance too far in either direction will affect the final brew in terms of extraction.

The Specialty Coffee Association offers a good benchmark with their “golden ratio” of 1:18. This works out at roughly 55g of coffee for each litre of water.

Keep in mind that this ratio is likely to vary from method to method, as well as according to personal taste; some will prefer a bitter, more intense brew, for instance, and may choose to use a slightly lower ratio.

Grind Size

Beyond brew ratio, Dale says that grind size is one of the most significant factors to consider when brewing filter coffee. It has a huge impact on flavour and extraction.

Almost all grinders will allow brewers to adjust the size of the coffee grounds. Larger grounds have a lower surface area, meaning they release flavour compounds more slowly, and therefore need a longer brew time. Conversely, smaller particles have a higher surface area, and release flavours more quickly, meaning less time is needed for brewing.

As such, different brewing methods will require different grind sizes. Espresso, for instance, requires a very fine grind, because the shot is extracted in less than a minute. In contrast, brewers using a French press typically choose a coarser grind, because the immersion method takes much longer.

For pour over and drip filter coffee, a medium to medium-coarse grind size is often used. However, keep in mind that grind size will also depend on how much coffee you’re brewing. If you’re brewing larger volumes of coffee (manually or with a batch brewer), which will take more time, adjust your grind size to be more coarse.

Water Quality & temperature

Water makes up about 99% of a cup of coffee. As such, it’s no surprise that good water is essential for brewing a quality cup. “You want to start with good, clean water, free of any colour and any aroma,” Dale says. “Filters or filtration systems will normally give you more control.”

When it comes to water temperature, Dale recommends a temperature range of 90ºC to 95ºC. “Much below 90 degrees, the thermal energy is not going to be enough to draw the best flavours from most coffees. [This is especially important for] lighter roasted coffees and the more interesting, [delicate] flavours.

“You want that temperature to be high enough to allow for the fast extraction of the most interesting flavors, but not so high that it creates negative flavours.”

Photo Credit: Kayla Phaneuf

The Bloom

The bloom is essentially the first stage of brewing filter coffee. Once the grounds have been added to the filter, a small amount of water should be poured over to wet them (often at a water-coffee ratio of between 2:1 and 3:1). The brewer should then wait for 30 to 45 seconds. This allows any CO2 in the coffee grounds to release, which reduces undesirable, astringent flavours and improves extraction.

Dale says that by pre-wetting the grounds at the beginning of the brew, you are more likely to finish with an even extraction.

“When you pour that water on, particularly if the coffee is really fresh, it will drive out any carbon dioxide caught in the coffee grounds,” he explains. “That helps extraction as well, because it means that whatever you pour in later gets closer to the coffee.”

It’s also important to make sure that all the grounds are saturated for the bloom, even if this means you need to pour in more water. Dale says: “A little too much water causes fewer problems than not enough water.

“You’re trying to make sure there are no dry patches in the coffee bed. So particularly if you’re brewing pour over, you’ll want to pour slowly at first, and make sure that any dry grounds you can see make contact with the water. Some people will also want to stir the grounds to help spread that water across it.”

Dale says it’s important to consider all of these variables. Not only does it lead to a good, well-balanced cup of coffee, it also gives the brewer more control over the process and improves consistency.

“I think consistency is the essential element,” Dale says. “Whenever you have consistency, you can taste the coffee and change something about the recipe.”

Photo Credit: Avery Evans

Manual Or Batch Brew?

Another important element to consider when it comes to brewing filter coffee is whether or not you’re opting for manual or batch brew. The main differences, Dale says, are batch size and brewing time.

To choose between the two, it’s important to understand what you want from your coffee. If you want a slower, more “human” approach with more direct control, for instance, you can choose from a wide range of manual brewing methods. These range from the ever-popular CHEMEX® to drippers like the V60 and the Kalita Wave.

While manual brewing does allow you more control, however, it is also difficult to replicate the same brew recipe time and time again. Dale says that if you want to offer a delicious, high-quality coffee consistency in large quantities, batch brew is the way to go.

Dale says that one such option is the Ottomatic®, a brewer brought to you by Marco and CHEMEX®. The Ottomatic® domestic filter coffee brewer automates the filter brewing process usually managed by a skilled barista in a specialty coffee shop.

By managing time, temperature, and turbulence, the Ottomatic® coffee maker facilitates even, consistent extraction and ensures that every cup of coffee brewed at home is premium and barista-standard. It also features an iced coffee mode.

“Because it controls a set of variables, it puts the control back on you to play with some of the others and get different results from a given coffee,” Dale explains.

Filter coffee is a great way to enjoy a wide range of beans. The filter removes any granules and results in a clean and clear cup, while the range of different filter brewing methods on offer means that every coffee consumer can find something that works for them.

However, no matter which filter coffee brewing method you choose, a firm understanding of the basics as well as a machine like the Ottomatic® will help you to prepare high-quality filter coffee from the comfort of your own home. In the end, the most important thing is that you enjoy the process and the results.