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Percolation Mechanics

P 1.07 Drawdown



The final phase in the mechanics of brewing is the drawdown. With mechanical brewing and pour-over, this phase initiates after the final addition of water. Any intervention into the coffee bed is not possible with most mechanical brewers. With pour-over coffee, however, many baristas elect to perform a final agitation of the coffee bed to level it out at this point. There is a range of approaches for this, but as a general rule, BH doesn’t advocate agitating into the coffee grinds. This has the effect of causing an excess of fines migration, which can cause a severe blockage of the pores in the filter paper below.


In this video, Matt demonstrates the effect of excessive agitation of the coffee bed on a brew dialled in for a 3-minute contact time. You will notice the total contact time draws out to several minutes longer than the recipe.




The Rao Spin

A method popularised by renowned coffee educator Scott Rao is to take hold of the filter cone and manually rotate it, creating a gentle whirlpool in the slurry. This can be very effective in creating a flat coffee bed and is particularly helpful in faster pour-over methods that involve only two pours. (See Lesson 3.04) Here is Scott in action explaining his method.




A repeatable means of creating a level bed is one similar to the process we suggest for blooming your coffee. With the help of a spoon or spatula, it involves a north–south motion with two or three repetitions, followed by the same motion from the east–west (hence, ‘NSEW’). This can be a very repeatable and fast process, with the drawback that it requires you to handle another tool, so it is a little less efficient than the Rao Spin.