For all immersion brew methods, it is important to ensure that no grinds have a head start over any others. Every successful immersion recipe we have encountered whilst researching this course requires baristas to add water to grinds (or, sometimes, grinds to water) in such a way that every individual particle is saturated as quickly as possible. However, coffee has a tendency to trap air pockets beneath the surface — sometimes for minutes into the brewing process. This is especially the case for brew methods that don’t involve manual agitation of grinds. In these instances, baristas need to be skillful and thorough with their use of a pouring kettle. A kettle stream, if poured in a way that creates the right amount of turbulence, will churn up the grinds and declump any areas that have pockets of air trapped beneath the surface. In general, the goal when first adding water to an immersion brew is to cause the grinds and water to temporarily fluidise. We will explore this concept in Lesson 1.03.
The difficulty in correctly saturating all the grinds is created by the shape of the brewer and the diameter and shape of your kettle’s spout. Variations in the design of brewing equipment mean no single approach can be universally applied to achieve the most complete wetting of the grinds. To better understand what approach to pouring is the most likely to wet all the grinds evenly and simultaneously, we designed an experiment: We used six separate approaches to pouring into domed cupping bowls:
- Centre pouring, slow (<5 ml/sec)
- Centre pouring, fast (>20 ml/sec)
- Pouring in spirals, slow (<5 ml/sec)
- Pouring in spirals, fast (>20 ml/sec)
- Manual agitation with 2 stirs
- Manual agitation with 4 stirs
We then examined which cupping bowl produced the least amount of bubbles rising to the surface over time. Bubbles appearing late into the brew process are a sure sign of a dry clump of grinds belatedly releasing trapped air.