Hey guys,
Welcome back,
Today, we’re diving into a deceptively simple but hugely influential aspect of brewing: agitation — specifically, how it shapes extraction, flavour, and the final clarity of our favourite filter coffee.
Whether you’re swirling your V60, stirring the bloom with a chopstick, or letting your kettle do the work, agitation is an essential variable in filter brewing. Yet it’s often misunderstood or completely overlooked. We will also include some tests and taste, extraction and solubility evaluation of 3 different brews with different forms of agitation using the same coffee and recipe.
So let’s get started.
To get deeper into this, we’ll pull insights from The Physics of Filter Coffee by Jonathan Gagné, By the end, you’ll have a much clearer understanding of why agitation matters — and how to use it deliberately to elevate your brews.
What Is Agitation in Filter Brewing?
Agitation is any physical movement or disturbance applied to the coffee slurry (the mixture of water and coffee grounds) during the brewing process. This can include:
- Stirring with a spoon or paddle
- Swirling your dripper or carafe
- Pouring water in a way that causes turbulence
- Tapping or shaking the brewer
- Using tools like the Tricolate diffuser or flatbed brewers with specific pouring patterns
At its core, agitation is about improving water-coffee contact. It’s a way to promote uniform extraction by ensuring all grounds are equally saturated and avoiding the common enemy of uneven flow: channelling.
Why Agitation Matters: The Science Behind It
According to Jonathan Gagné, who spent years analysing coffee through the lens of physics and fluid dynamics, agitation has a measurable impact on:
- Wetness uniformity
- Bed homogeneity
- Extraction yield consistency
In The Physics of Filter Coffee, Gagné points out that even a seemingly minor variable like a 5-second swirl can change the extraction curve, especially in cone-shaped brewers like the V60. His research — including high-speed imaging and precise Total Dissolved Solids (TDS) measurements — shows that non-agitated brews often suffer from under-extraction at the periphery of the bed and over-extraction in the centre.
This leads to cup profiles that are flat, astringent, or just a bit lifeless. When done right, agitation can even out the playing field, making each coffee particle do its fair share of work.
Different Types of Agitation – And What They Do
Not all agitation is created equal. Here are the most common techniques and how they interact with the brew:
Bloom Stir
Used during the initial wetting phase, a bloom stir helps:
- Saturate all the grounds quickly
- Dislodge carbon dioxide trapped in the bed
- Kickstart even extraction from the get-go
According to Gagné, this is often the most beneficial form of agitation, especially when using fresh, high-CO₂ coffees.
Tip: Use a spoon or paddle to stir gently in multiple directions for 5–10 seconds during bloom. Avoid scratching the filter paper, especially in V60s.
Pulse Pouring with Natural Turbulence
Rather than pouring all your water in one go, pulse pouring introduces waves of turbulence that disrupt channel formation. This works well in brewers like the Origami or Kalita, which rely on flat beds.
Gagné suggests that higher turbulence is especially important in flat-bottom brewers where flow rates are slower and the risk of clogging is higher.
Swirl and Spin
The swirl is a crowd favourite — but there’s nuance. A quick swirl:
- Evens out the coffee bed
- Breaks up clumps
- Helps redistribute fines
However, Gagné warns that swirling too aggressively or too late in the brew can collapse the bed, compacting the grounds and slowing drawdown, which increases the risk of over-extraction and adds bitterness or muddiness to the cup.
Top Tip: Swirl gently after bloom or midway through the brew, not near the end.
End-of-Brew Stir or Tap
Some brewers finish with a stir or tap to flatten the bed, reduce dome-shaped clumping, and aid even drawdown.
Baristas in competition often do this to get precise, replicable drawdown times, but it’s risky if your grind is very fine or if you’ve already used a lot of agitation earlier in the brew.
How Much Is Too Much?
While agitation helps promote uniformity, over-agitation introduces problems. Here’s what you want to avoid:
- Over-extraction: If you agitate too much or too late, you extract more bitter, woody compounds from the grounds.
- Fines migration: Tiny coffee particles can settle at the bottom and block flow, especially in brewers with narrow exit holes.
- Collapsed coffee bed: Aggressive movement can flatten the bed and cause water to pool unevenly, leading to longer brew times and higher TDS, but not in a good way.
Gagné’s research emphasises the importance of precision and consistency. Don’t just agitate randomly — treat it as a controllable input, just like grind size or water temperature.
Practical Brewing Tips: Dialling in Agitation
Here’s a framework you can try to help you experiment intentionally:
Method: Bloom Stir + Gentle Swirl
Works Best For: Light-roasted, fresh coffees with high CO₂
- Pour 50–60g of water for the bloom
- Stir gently for 5 seconds to saturate all grounds
- At 45 seconds, begin pulse pouring
- After the last pour, give one gentle swirl
This approach helps with even extraction and maintains a clear, clean cup, especially on a V60 or Origami.
Method: No Stir, Just Turbulent Pour
Works Best For: Medium-roasted coffees, coarser grind
- Skip stirring during the bloom
- Pour in pulses with a high starting height to generate natural turbulence
- Use a final swirl before drawdown starts
This reduces agitation-induced fines movement while still achieving evenness through the pour dynamics.
What the Pros Say
Agitation needs to be implemented into your recipes. What works for a Hario Switch might not work for a Kalita Wave. Competitive baristas often spend days testing variations of swirling, stirring, and pouring just to lock in a flavour profile and get the best out of the coffee.
Meanwhile, Gagné’s data-backed approach gives us the tools to measure outcomes — TDS, extraction yield, and drawdown time — so we can brew with intention instead of guesswork.
The Tests:
Recipe: V60, 300g water, 18g, 3 pours – 60g bloom, 45s 150g, 1:30 300g. Washed Kenyan.
Test 1: no agitation, controlled flow rate
Drawdown time: 3 minutes 24 seconds
Taste evaluation: muted, medium, bright acidity when cooled, nutty body, but too short and flat finish
Test 2: Bloom stir, gentle swirl
Drawdown time: 3 minutes 40 seconds
Taste evaluation: smooth but rich, syrupy body, vibrant stone fruity acidity, balanced and medium finish, just what we were expecting from this coffee.
Test 3: natural agitation (turbulent pour)
Drawdown time: 3 minutes 38 seconds
Taste evaluation: balanced, drinkable, sweet and syrupy body, bright acidity as cooled, slightly dry but lingering finish, we preferred the taste of this test compared to the bloom stir. But out of the three, the bloom stir, gentle swirl and the natural agitation tasted the best.
Summary
Agitation isn’t just some optional flourish. It’s one of the most powerful tools in your brewing toolkit — if you use it thoughtfully.
Whether you’re aiming for more clarity, sweetness, or consistency, understanding when and how to agitate can help unlock that next level in your brews. Remember: consistency is key. Don’t change your agitation pattern without adjusting your grind, dose, or pour rate to match.
As always, brew with curiosity, evaluate the taste differences, and take notes
Until next time,
Stay curious, happy brewing, catch you on the next one.
Feel free to check out our other pour-over articles on flow rate and a starter’s guide to help up your brew game!
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