Achieving High Extraction with Low Agitation

The brewing method we'll explore: using the Pulsar's dispersion screen atop the Orea V3

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At first glance, low agitation and high extraction might appear to be at odds. Agitation facilitates the thorough mixing of coffee grounds with water, typically increasing extraction and making extraction more even.

Yet, agitation also speeds up the migration of fines, leading to a higher likelihood of filter clogging. Clogging can intensify channeling and bypass, resulting in the underfiltration of more astringent compounds by the coffee bed. Consequently, clogging is often linked with astringency and undesirable flavors^[B].

The Challenges of High Extraction Brews

I’ve always been a fan of high-extraction coffee and generally aim for at least 22% extraction yield when brewing. In my experience, high-extraction coffees tend to offer greater flavor complexity and sweetness, mirroring the flavors found during cupping. Translating these cupping flavors to pour-over has been a long-standing ambition of mine.

However, achieving high extraction typically requires finer grinding, more agitation, or a combination of both.

Finer grinding increases the likelihood of clogging due to the higher production of fines from more frequent cuts. As previously mentioned, agitation can also lead to clogging.

This makes the pursuit of high extraction a challenging and sometimes frustrating endeavor. Even with burrs that generate minimal fines (I use the 98mm SSP Brew burrs), avoiding clogging with fine grinding and high agitation is nearly impossible. In such cases, despite achieving high extraction and enjoying the complex flavors and sweetness, one often has to endure a rather poor mouthfeel, more precisely: astringency.

The Origin of the Low Agitation Method Idea

The coffee enthusiast community has been paying more attention to astringency issues lately. I shared my concerns about excessive astringency at high extractions with numerous international enthusiasts on Discord. However, most don’t aim for such high extraction yields, making coarser grinding the simplest solution. This not only reduces fines and the risk of clogging but also decreases the number of times the coffee is cut, which lowers the release of astringent compounds from cell wall damage that are difficult to dissolve in water (for more details, please see Jonathan Gagné’s article).

Yet, I wondered if it was possible to maintain high extraction while reducing astringency. SEY, a coffee shop in Brooklyn that I admire, shares a similar philosophy of “maximizing extraction yield to replicate cupping flavors.” Most of my daily brews are with their coffee. Out of curiosity, I reached out to them about their brewing recipe and shared my thoughts on astringency.

I wasn’t expecting a response, given their likely inundation with order inquiries. To my surprise, I received a detailed reply two days later (presumably from the renowned “SEY Lance”?). The message read:

For filter coffee, I have my grinder (Nautilus w/ SSP Brew Burrs) at around 250 and 300 microns.

Our water is: Mg - 15ppm, Ca - 20ppm, Bicarbonate (KH) - 15ppm

For the sake of simplicity, we’ll talk about V60. As you know, we’re really working towards figuring out how to increase EY. With our coffees, you should be able to achieve 24%+ for most Latin coffees and 26%+ for most African coffees. Our brew times are between 6 and 8 minutes for complete draw-down times. looking for a 1.4%—1.5% TDS.

A simple technique to try: 16g dose at a 1:20 ratio. Bloom for 60 seconds with a very gentle stir and swirl for complete saturation. With a Melodrip, do 75g pulses until the desired out weight with gentle swirls between pulses. This should result in somewhere between 6 and 8 minutes of total brew time. If longer, I wouldn’t worry unless there are off flavors in the cups.

Something to note is that with really high EYs the coffee really changes and improves as the coffee cools.

To mitigate astringency, I’d recommend trying a Melodrip and using zero agitation. For us, we’ve noticed that although agitation helps increase EY, it also increases astringency. So, trying to get high EYs without using agitation is kind of the trick.

Lance’s (or the person I believed to be Lance) suggested solution was to use extremely fine grounds, slightly coarser than espresso, to increase extraction yield while using a Melodrip (a showerhead-like device) to minimize agitation, as agitation was found to increase astringency in his experience. This might also be partly due to the reduced risk of clogging from less agitation.

The last sentence of their email is the crux of this article: the key is how to use a low agitation method to achieve high extraction yield.

Potential Problems with Low Agitation

A few potential issues come to mind:

• Grinding extremely fine will undoubtedly produce more fines than coarser grinds. Even with reduced agitation, could clogging still be a significant risk?

• Without sufficient agitation, coffee at the bottom of the dripper might be under-extracted. Can high extraction yields still be achieved if the bottom is under-extracted?

Interestingly, SEY uses the same burr set as us (the 98mm SSP Brew V1), suggesting direct applicability of this recipe. I adapted this recipe using the equipment I had, opting for the less bypass-prone Orea V3 with negotiated flat filters instead of the V60, and the dispersion screen from the Pulsar instead of the Melodrip.

After thorough experimentation, I’m pleased to report that both potential issues are either non-existent or minor. The likelihood of clogging is significantly reduced compared to my usual brewing methods, and achieving an extraction yield of over 24% is straightforward.

Recipe Introduction

Grind size reference
This is SEY's Las Perlitas (Washed Colombian Field Blend) ground with 98mm SSP Brew, burr gap set to 225 µm from lock

Here are the detailed parameters and brewing steps:

• Coffee to water ratio: 16g:320g (1:20)
• Water temperature: 100°C
• Brewing water: distilled water, re-mineralized post-brew (minerals are added directly to the brewed coffee^[C]).
  • Aim for water with 30–40GH, 15–20KH^[D], with equal amounts of Ca²⁺ and Mg²⁺.
  • If unsure about your water, normal tap water with a low TDS is acceptable.
• Grind size: Burr gap set between 200 to 300 µm from lock.
  • Only slightly coarser than typical 9 bar espresso settings.
  • I used the Lagom P100 with the 98mm SSP Brew burrs, with grind settings between 3.0 and 4.0.
  • If your grinder produces more fines, consider a slightly coarser grind.
• Target concentration (TDS): 1.35%+
• Target extraction yield: 24%+

Required Equipment

• Very lightly roasted coffee
  • Given our aim for very high extraction yields, it’s crucial that the coffee tastes good when highly extracted. Lighter roasted coffees typically fare better at high extractions.
  • Roasteries I’ve had success with include SEY, The Picky Chemist.
• Dripper
  • Any dripper will do. SEY uses the V60, while I use the Orea V3.
  • To increase extraction, use a plastic dripper with better heat retention if possible.
• Grinder, filter papers, carafe, digital scale, and other basic pour-over gear (a pouring kettle might not even be necessary!).
• Device to reduce agitation
  • The Melodrip or the dispersion screen from either the Pulsar or the Tricolate all suffice. Alternatively, a small spoon can be used to catch water poured from the kettle, as demonstrated in this technique by pocketsciencecoffee. Any method that minimizes agitation to the coffee bed is suitable.
• A WDT tool
  • Alternatively, a spoon, chopsticks, or glass stick can be used to stir the coffee bed during the bloom.

Detailed Brewing Steps

Equipment setup during brewing (note: the disperser isn't needed during bloom)
The background is the cluttered NTU Coffee Club clubroom

The following steps are tailored to the Orea V3 with negotiated flat filters and the dispersion screen from the Pulsar:

1. Fold the Orea’s flat filter in a cross pattern, press it into the dripper with the negotiator, and rinse the filter.
2. Measure 16g of coffee, grind, and pour into the dripper.
3. Flatten and evenly distribute the coffee bed in the dripper using a WDT tool.
4. Start the timer, add 40g of water for the bloom, the dispersion screen is not needed at this stage.
5. Immediately perform a Wet WDT with the WDT tool, gently stirring to avoid vigorous agitation that could lead to clogging.
6. After the Wet WDT, gently spin the dripper (a Rao Spin) to ensure a flat coffee bed without holes from the WDT tool.
7. Place the Pulsar’s dispersion screen on top of the dripper. The screen weighs 50g, so the scale should now read 90g.
8. At 1:00, pour in 70g of water. Begin with a larger amount for even distribution in the dispersion screen, then pour at a rate of 2.5–3g/s.
9. Gently spin the dripper to flatten the coffee bed.
10. When the water level above the coffee bed is about 0.5–1cm, add another 70g of water and repeat steps 8 and 9. After four repetitions, the scale should display 370g, indicating a total water use of 320g (accounting for the 50g weight of the dispersion screen).
11. Allow the water to fully drain. The total brew time should be about 7–9 minutes, but as long as it’s under 10 minutes, flavor issues are unlikely in my experience.
12. Re-mineralize with Lotus Coffee Brew Water. Add one drop each of CaCl₂ and MgCl₂ solutions, and two drops of NaHCO₃ to the brewed coffee. This results in approximately 15 ppm of Ca²⁺, Mg²⁺, and HCO₃^- as CaCO₃.

Brewing Log and Discussion

One of the more successful brews, achieving the target TDS and extraction yield
The TDS and extraction yield were 1.37% and 24.47% respectively

Graph showing changes in pour rate (blue line) and weight (brown line)

The graph illustrates similar time intervals between the four pours post-bloom, indicating minimal reduction in flow rate towards the end of extraction. This suggests that clogging was not severe. An 8-minute total brew time might be longer than what many are accustomed to, but the stable flow rate throughout the brewing process is a positive indicator.

This recipe is remarkably stable and boasts the highest success rate among the high-extraction methods I’ve tried. The minimal agitation significantly lowers the chance of clogging, while the fine grind supports a high extraction yield. The resulting cup is exceptionally complex, sweet, but also clean and transparent. If replicating cupping flavors is the ultimate brewing goal, this recipe is a standout success.

It’s important to note that the dispersion screen is not used during the bloom, as outlined in step 4. This detail is crucial. In our tests, using the dispersion screen during the bloom, even with Wet WDT and Rao Spin to ensure the coffee and water mix evenly, reduced the extraction yield by about 2%–3%. This phenomenon is puzzling and warrants further investigation.

Conclusion

I believe those accustomed to high-extraction coffee will appreciate the clarity this recipe offers, while those who prefer lower extractions will be intrigued by the complexity and sweetness of higher extractions. Regardless, if you give this recipe a try, I’d love to hear your thoughts!

Although this recipe requires an additional dispersion screen, alternatives like spoons should also work well. During brewing, the time intervals between pours post-bloom can serve as an indicator of success. With low agitation, these intervals should be similar. If you notice a significant decrease in flow rate towards the end of brewing, indicating clogging, you may need to further reduce agitation or adjust the grind coarser.

I hope this recipe helps you brew coffee that is complex, sweet, and transparent! If you have any questions or wish to share your experiences, feel free to connect with me via IG!