What I've learned from no-bypass brewing
Lessons from Pulsar and Filter3
A few years ago, Jonathan Gagné coined the term “no-bypass brewing.” The phrase refers to brewers that force all of the brewing water to pass through the coffee bed. In this post I’d like to discuss a few simple lessons no-bypass brewers have taught me or reinforced.
The “other” type of bypass
The term “bypass” usually refers to water seeping through the wall of a pourover filter above the level of the grounds. This is distinct from the bypass feature of a batch brewer.
Batch brewers such as Fetco and Curtis and Bunn machines have a secondary water-dispensing spigot positioned near the inner edge of the basket. When the user opts to use some bypass, the bypass water pours into the basket but outside of the filter. Batch-brew bypass dilutes the final brew akin to how adding water to an espresso creates an Americano; the primary effect of both is dilution. One may opt to use the bypass valve when brewing very large batches relative to the basket diameter. The theory is that if the coffee bed is too deep (eg greater than 5 cm), it is better to dispense some water through the bypass valve than to grind coarse enough to allow all of the brewing water to pass through the bed in a reasonable amount of time. In some cases, the coffee bed may be so deep that one’s grinder cannot grind coarse enough to provide sufficient flow for all of the brew water to pass through the bed in a reasonable amount of time.
First-generation no-bypass brewers
The first generation of no-bypass brewers included the Tricolate and the NextLevel LVL10. The first and most surprising lesson was how much pourover bypass decreased potential extraction levels relative to what could be achieved with a no-bypass brewer. It is not difficult to reach extraction levels as high as 29% with coffees from Kenya and Ethiopia in a no-bypass brewer. That is not to say those extraction levels are optimal; it is simply illuminating that the extraction ceiling is so much higher in a no-bypass brewer. Although one can find claims online of people extracting ~29% in a v60 or Kalita, such claims are often due to inaccurate measurement or use of grinders that produce extremely low proportions of fines and boulders; with such grinders, no-bypass brewer extractions can exceed 30%. The more realistic limit with common grinders, accurate tools, and proper measurement technique is nearer 24%.
Other findings either learned from, or reinforced by, using a no-bypass brewer included the benefits of both dry and wet Weiss Distribution Technique. Lance Hedrick was the first person I am aware of to apply wet WDT, or WWDT, during a bloom. The method is easier to perform beneficially in a flat-bottomed no-bypass brewer than in a pourover. The relatively shallow, flat-bottomed bed of the first generation no-bypass brewers also lends itself well to dry WDT, something previously used to improve espresso puck distribution, but rarely used in filter brewing.
Second-generation no-bypass brewer
The NextLevel Pulsar represents what I consider the second generation of no-bypass brewers. The most important design change was the addition of a valve capable of stopping and modulating flow of liquid out of the brewer. Other improvements included lowering the shower screen, slowing the flow of water through the shower screen, and narrowing the brewer to increase bed depth in the popular ground dose range of 20g—25g.
Closing the valve during the bloom allows one to maintain a slurry above the grounds, which helps keep the slurry temperature higher. Such a “wet bloom” presumably makes it more likely the grounds will fully saturate with water. I have had better average results using a wet bloom than when allowing the bloom to dry out, though I cannot be sure of the reason.
A surprising lesson from the NextLevel has been the impact of bloom time on cup quality. Comparing bloom times in a pourover in an apples-to-apples way is nearly impossible, because the comparison is confounded by if, and for how long, the slurry dries out. The NextLevel’s valve allows us to compare the results of bloom times while maintaining a slurry above the grounds in all cases. Many have noticed shorter bloom times tend to produce more aromatic, delicate brews, while longer blooms yield less aroma, and heavier cups.