July 26, 2022

How does agitation affect filter coffee brewing?


Whether in a coffee shop or at home, the ultimate goal with brewing filter coffee is to achieve even extraction. By doing so, you can get the right balance of flavours out of your coffee.

However, there are a number of variables to consider when brewing filter coffee, including brew temperature, extraction ratio, and grind size. One extraction variable that can often be ignored is agitation. 

Agitation is the process of disturbing or disrupting the coffee bed, either by pouring water directly onto it, or by stirring or swirling the mixture. Just how much you should agitate while brewing filter coffee is a topic of debate among coffee professionals, but it plays an important role in extraction.

To learn more about how agitation influences filter coffee brewing, I spoke to four coffee championship winners. Read on to find out what they told me. 

You may also like our article on achieving even extraction with filter coffee drippers.

agitating coffee grounds in a siphon brewer

What is agitation?

There are several different types of agitation which can be used when brewing filter coffee. These include stirring or swirling the slurry, as well as various methods of pouring water onto the ground coffee – such as pulse pouring

Each method of agitation will affect extraction differently, which ultimately influences the overall flavour profile.

Stirring is one of the most common forms of agitation in filter coffee brewing. This method involves using a spoon or other utensil to mix the coffee grounds and water, often for a specific amount of time. 

However, different stirring techniques can have differing effects on extraction. For example, stirring the slurry in a figure of eight pattern is a method commonly used by baristas to evenly distribute the grounds in the water.

Swirling the brewer is another way to agitate the slurry that can improve the consistency of extraction. This method is more commonly used by less experienced baristas, as it is easier to and quicker to do than stirring.

Pulse pouring is also another form of agitation. This process involves pouring water onto the ground coffee in short bursts, which can be an effective way to experiment with your filter coffee brewing. 

Pulse pouring can be highly controlled, too, as you can adjust the number of “pulses” as well as the volume of water added with each pulse.

brewing multiple cups of pour over coffee

How much agitation is best for filter coffee brewing?

In Everything But Espresso, coffee professional Scott Rao explains that “agitation always accelerates extraction and usually improves the uniformity of extraction”. So what is the optimal level of agitation for filter coffee?

Ultimately, extraction is a result of several variables, including grind size, origin, roast profile, water temperature, and brew time. Agitation, meanwhile, has its own effects on extraction. 

Agitation is an essential part of brewing filter coffee. Without it, the water molecules would not be able to extract enough volatile compounds from the ground coffee – resulting in weak and sour-tasting underextracted coffee.

However, too much agitation means that too many volatile compounds could be extracted, which may lead to a hollow and bitter-tasting coffee. 

Your chosen brewing method is also another variable to consider. Water distribution plays an important role in immersion brewing as the coffee grounds are fully submerged in the water throughout the total brew time. By evenly submerging all of the coffee grounds in the water as quickly as possible, you are more likely to achieve even extraction.

However, with pour over brewing, the brewer needs to periodically pour water over the coffee grounds, as opposed to adding all of the water at once. This gives you more control, but also means that agitation occurs naturally at certain points.

siphon coffee brewers lined up on a counter

Agitation in immersion brewing

To achieve the best results with immersion brew methods, the coffee grounds must be fully submerged in the water for as much of the total brew time as possible. Common immersion brew methods include the French press, the syphon (also known as the siphon or the vacuum pot), and the AeroPress.

Agitation plays an important role in the saturation of coffee grounds as it helps to break up any dry clumps. This means that the water molecules are then able to saturate the grounds, resulting in more even extraction.

Regine Wai is the 2022 Malaysian Brewers Cup Champion. She explains that while agitation is necessary for any immersion brew method, it can be more difficult when using a syphon. This is because the water temperature continually increases in the brewing chamber, as it is placed over a gas burner or other heating device throughout most of the brewing process.

“When I brew with a syphon, I use a bamboo stick to agitate my brew,” she says. “Not only does this mix the coffee grounds with the water to release the flavours, it also helps to control the temperature. 

“By agitating [the slurry] a few times you can reduce the [brew temperature] by a few degrees and have more control over the extraction process,” she adds. “Of course, this also depends on the brew recipe and extraction variables you are using.”

different types of pour over coffee brewers line up

How does agitation affect brewing with pour overs?

Most pour over brewers, such as the Chemex or the V60, rely on gravity to draw the water through the coffee grounds. However, the amount of agitation you need will differ depending on the type of brewer you are using.

When brewing a pour over, some coffee professionals believe that a quick stir can help to break the “crust” that can form at the surface of the slurry. This allows water to move through the bed of coffee grounds at a quicker rate – minimising the risk of overextraction. 

However, if you stir for too long or too vigorously, the fines can migrate to the coffee bed, which can prolong the total brew time or even cause channelling. 

In order to minimise any risk of under or overextraction, baristas and home brewers can pulse pour into the centre of the coffee bed throughout the entire brew. This is a more repeatable technique for coffee professionals and consumers – no matter their experience level. 

But for many coffee professionals, preparing a pour over can be more complicated than immersion brewing, which means you need to be careful with the amount of agitation you apply.

Stathis Koremtas is the 2022 Hellenic Brewers Cup Champion. He tells me that agitation is one of the main factors which increases the rate of extraction.

“You have to ask yourself if you want to increase the extraction rate because it will affect the flavours you extract,” he says. “Ultimately, it depends on the coffee you’re using.”

He adds that there is no right or wrong answer when it comes to the amount of agitation. Ultimately, it comes down to the coffee you’re brewing.

brewing pour over coffee in a chemex

Achieving consistent results

No matter which coffee you’re brewing, consistency is always essential, and agitation is important when it comes to achieving this.

Gabriel Carol is the 2017 and 2018 Romanian Brewers Cup Champion and the owner of PAGA Microroastery in Bangkok, Thailand. 

He tells me that when he visits coffee shops, inconsistency in brewing techniques is one of the biggest problems that he notices.

“Sometimes a barista will brew the same coffee, but in different ways,” he says. “This means that sometimes I get a great-tasting coffee and other times an average coffee, even if both were made using the same beans.

“It’s a result of human error and a lack of training,” he adds. “I’ve seen baristas pour water in different ways; some apply a lot of agitation, while others apply barely any.”

Techniques like pulse pouring into the centre of the slurry can be used to overcome these inconsistencies, as well as stirring and swirling in a particular pattern for a specified amount of time. 

However, each coffee is different and will require a different approach to agitation.

Mariam Erin is the 2021 UAE Brewers Cup Champion. She provides some guidance on how to alter your agitation technique according to different variables, such as processing method and roast profile.

“I prefer to control the pour flow rate and focus on overall brew time,” she tells me. “For example, for a natural coffee that is roasted medium to dark, I will use a faster flow rate so I can extract fewer bitter-tasting compounds, and increase the acidity.

“However, for a washed light roast, I will pour slower in four or five stages,” she adds. “This way I can enhance the body and balance out the increased acidity.”

preparing pour over coffee in a V60

When it comes to brewing filter coffee, the most appropriate agitation technique is largely dependent on the beans you are using and your experience level. There is no right or wrong method; each has potential to bring the best out of your coffee.

However, it’s still important to take care when agitating your coffee bed. By stirring, swirling, or pulse pouring in a precise and measured way, you’ll be more likely to achieve even extraction with more desirable flavours and characteristics.

Enjoyed this? Then read our article on brewing larger volumes of coffee at home.

Photo credits: Stathis Koremtas

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