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Variables in Immersion Brewing

IM 1.09 Recap and Glossary

  • Wetting coffee grinds at the beginning of the brewing process helps to make extractions more even.
  • The crust forms as a result of the roasting process, which causes coffee beans to become microporous. The pores in roasted coffee typically measure 20–50 nanometres in diameter. 
  •  Whole roasted coffee beans will not sink below the surface of water — even if you leave them in water for over 24 hours. 
  • When cupping, the convention established by the Specialty Coffee Association is to break the crust 3–5 minutes after the pour. Our research suggests that the highest extraction yields are achieved when the crust is broken after 5 minutes. 
  • The buoyancy of roasted coffee grinds is reduced as the gases trapped inside them are released.
  • Agitation can significantly increase the extraction yields of coffee: We found that 16 stirs in a cupping bowl produced a 20% higher extraction yield than just 2 stirs.
  • Stirring in a whirlpool pattern is not an efficient means of creating turbulence.
  • We advocate a NSEW or bottom-to-top stirring method. 
  • Stainless steel filters cannot retain particles smaller than approximately 50 µm in size.
  • Once oils penetrate into the hollow spaces in the fibres of cloth filters, they’re extremely difficult to remove. Over time, the oils become rancid, releasing a spectrum of unpleasant flavours that can make their way into the brew.
  • In testing, we found the average concentration of brewed coffee at the bottom of a set of cupping bowls was 6% stronger after 8 minutes of steeping and 8% stronger after 16 minutes. We found a similar tendency with French press coffee. 


New Words

Cezve (ibrik)  The Turkish name for a brewing device used to prepare Turkish and Arabic coffee. It is typically made of copper or brass, or, more recently, stainless steel, glass, ceramic, or aluminium. 

Jug coffee  A simple immersion brew method prepared in the same way as a French press except jug coffee doesn’t involve a press or any kind of filtration.