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Agitation in brewing

Agitation is a factor that very hard to have a quantitative standard. For example, we can say on this brew we use 20g coffee, 90°C water, and even C40 28 clicks grind size, but it is hard to say “X” level of agitation. Even so, we still care about it a lot.

Why agitation matter? Many people think agitation closely related to extraction yield. I think it is correct in some extents, but not about increase or decrease, is about even or “balance”. I mentioned in my previous posts that if we “cut” a dripper from middle, more soluble will be dissolved from the coffee on top half than bottom half (especially for cone shaped drippers). If the coffee ground stay in the same position during the whole brew, technically we will get a 50% over extraction + 50% under extraction cup of coffee. To avoid this situation, we use our pour to “stir” the coffee. In circle pour, we want to use the power of spiral to get coffee ground moving and reach all the coffee ground. In center pour, we want to use the down force of water flow to keep the coffee ground in two sides move regularly.

More agitation means better brew? Everything has its bad side and the same to agitation. The side effect of agitation is clogging. When we agitate the coffee ground, the micro fines are also moving. And when we stop, the micro fines are either attached to the filter, or get together and sunk to bottom. It will slower the flow rate on both ways especially latter. That’s why we recommend to agitate less and use filters that have higher crepe to solve the clogging problem.

There are many factors on agitation like the height of water stream or speed of circle pour that we can talk about in the future. And the agitation in here means the coffee ground movement that affected by water stream from kettle, does not include actions like using stick to stir or the famous “Rao spin”.