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Variables in Immersion Brewing

IM 1.08 Decanting Coffee

Separating the Beverage from the Grinds

For immersion brew methods that don’t involve fine filtration, the brewed coffee needs to be decanted from the surface. With cezve coffee made in Turkey, it is customary to pour the slurry into a serving cup, leaving the grinds to percolate to the bottom. But with French press, cupping, or jug coffee, the brew is decanted from the surface. If you serve several beverages from the same vessel, will the first and last cups served end up tasting the same? We have found that the upper layer  of a brewed coffee tends to be weaker than the bottom layer. 

To understand the degree of gradient that exists, we designed a simple test with the help of 2009 World Barista champion, Gwilym Davies, comparing the total dissolved solids (TDS) of brew drawn from the top of a large French press with the TDS of brew drawn from the bottom (1 cm above the top of the coffee bed). We also measured the strength of the coffee in a cupping bowl to see whether a smaller vessel produces a smaller difference in gradient. Our research mirrors an experiment by James Hoffmann, who found that the bottom portion of a freshly extracted espresso was far stronger than the top part. 

At BH, we think the best practice when serving a static immersion brew such as a 2-litre French press is to decant the entire contents of the brew into a separate, preheated flask, pouring very slowly to avoid letting grinds from the top of the coffee bed flow into the flask. The decanted brew can then be stirred, without worry about incorporating the grinds from the coffee bed into the beverage. After you have thus homogenised the layers in the decanter, it is ready to be served. 


Cupping Bowls Experiment

  • Brew ratio: 10 g:165 g. 
  • Water Temperature: 99°C water 
  • The coffee used was Ethiopia Banko Chekchele, roasted by Gwilym at Naughty Dog roastery in Jilove,