Last month a new controlled study of brew times in French press coffee was released. Conducted by Daniel Drazenovich, Chief Technical Engineer for the micro roastery Old Wwworld Cafe, the process and findings were quite interesting and worth a read. (See, "Perfectly Timed French Press Coffee".)
The Coffee Catcher's Nate Jones had the following thoughts on the study:
"It certainly makes intuitive sense that the surface area of grounds exposed to water coupled with the total volume of grounds should affect the timing of coffee brewed. Personally, I think the 200 degree pour is a bit on the low side, but I have no reason to supposed that that would comprehensively skew the results.
"This reminds me of an all day experiment I've been wanting to do involving brewing French press coffee by visual cues. I do it, and John [Custer] does it, but I haven't had a chance to figure out exactly what I'm reacting to in terms of sight, smell or perception of time that tells me when to press. I think the color of the crust on the top of the coffee does change as the brew continues, perhaps as slows, but I can't quite verbalize those cues yet. Anyway, this chemistry-heavy approach reminded me that sometime soon I'd like to do a controlled direct-perception series of brews and evaluate the results."