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Percolation Mechanics

P 1.04 Preparing the Coffee Bed

Preparing the Coffee Bed


Levelling Dry Grinds

For batch-brewing machines, it is necessary to prepare the coffee bed in a way that promotes even extraction. This is because most large-scale mechanical brewers don’t allow you to manually access the coffee slurry during the brew cycle (the amount of time the water takes to pass through the coffee bed). Unlike with pressurised extractions such as espresso, in percolation brewing there are no advantages to compressing the coffee grinds by tamping them. Instead, the coffee grinds need to be evenly distributed across the base of the filter cone in a way that doesn’t cause any smaller particles to migrate downwards onto the surface of the filter paper.


Gif of horizontal palm-tapping


As we suggested in the Barista One course, we advise you to practice horizontal palm-tapping as a means of achieving a homogenous mix of particles with an even density and a level surface. However, we do not recommend the practice of vertical palm tapping in the same way we do for espresso distribution. This practice is helpful in espresso distribution to break up clumps and air pockets. But clumping is far less of issue with percolation brews. This is because the optimum grind settings are usually much coarser for percolation brews due to the longer brew cycle. On coarser grind settings, grinds also move more quickly through the burrs, which helps to prevent grinds from clumping together.


Building a Nest



To ensure all the coffee grinds are uniformly saturated early on in the brewing process, it can help to hollow out the centre of the coffee bed into the shape of a bird’s nest before you add the water. This is particularly relevant for cone-shaped pour-over designs such as the V60 or Chemex and small batch designs such as the Moccamaster, which are based on the Melitta compatible filter shape. The nest shape encourages the water to penetrate the bottom-most section of the coffee bed as it begins to saturate the coffee grinds.