In the past week, I have had several conversations on pour overs and an observation was brought up that I have often thought about—isn’t h (hydraulic head) dropping as the pour over drains, which would cause a drop in flow, resulting in elongated water contact time, yielding over extraction? So isn’t this exactly what a continuous pour is trying to reduce, fluctuation and over extraction? The answer is yes, and a practical solution for the potential over extraction during draining exists. On the graph, I have simulated what I theorize a typical flow profile would resemble in a V60 or Chemex for both a pulse pour and a continuous pour.
Let’s break down the graph. For the first few seconds (after blooming) the filter is typically filled with water, this is shown by the sharp and immediate increase in Q. Second, for the continuous pour (in black) the water level in the pour over is held constant, but for the pulse pour, the water level drops and then rises with the next pulse. This is clearly seen by the wavy blue line. Third (if the entire pour over apparatus is on the scale), the scale reads the desired water weight based on your coffee to water ratio and no more water is added. Finally, the water is allowed to drain.
Anyone who has done a pour over realizes how excruciating it is to wait for that drain period to end. I swear it never ends, especially when the customer needs it to-go and is in a hurry.
But back to the observation, both ways to pour result in the long drain time. This is fairly easy to overcome with a V60 and most of us have probably seen at least one shop that has the V60 suspended above the glass server (or mug, see next picture). With the V60 suspended and the glass server on the scale, simply pour water until the scale reads the desired water weight and pull the server out from underneath the V60. The V60 will drain, but not into the server. Now you should have the correct coffee to water ratio in the server without the draining phase. Personally, I believe this yields a better pour over, but I would love to hear other opinions and experiences.
Great, well what about a Chemex or similar brew method where the funnel cannot be separated from the server. Bloom your Chemex and then tare the scale. Quickly fill the Chemex to the brim and read the scale. Record this value. The value recorded will be very close to the weight of water your Chemex holds in the upper portion. Now, in the future, if you want to do a 40:600 Chemex and the upper portion holds 50 grams of water (from your recorded value) simply add water until the scale reads 650 grams and pull off the Chemex filter. This will result in 600 grams of water in the bottom of the glass and 50 grams in the upper portion of the glass. Therefore, eliminating the drain time while preserving the coffee to water ratio.
I hope that one of these solutions will be helpful. Again, I love feedback and if you feel you achieve a better tasting cup with the drain time included, let me know. I would love to explore why that may be.
Next post I will be looking at the migration of fines in the coffee bed and the impact this may have on your pour over. Also, I hope to have some exciting news about potentially getting some lab space and testing various pour over theories to bring some substance to these arguments.