I’m familiar with what the bloom is and why we do it. But all of the instructions and guides about pour-over coffee I’ve ever seen recommend a specific time to let the coffee bloom before continuing with the brew. 40-45 seconds seems to be the most common consensus.
But I have to assume that every coffee setup is going to be a little bit different. Small changes in the freshness of the beans, the size and shape of the grind, the temperature of the water, maybe even things like the mineral content of the water? - all of these factors and more are going to have at least some effect on how much CO2 the coffee wants to offgas and how long it takes. So, “45 seconds” seems like a good guideline or rule of thumb, but I would imagine that some brews need less time and some need more.
So, if I want to gauge my bloom time by my senses instead of by the clock, what should I look for? I have noticed that toward the end of the bloom, the coffee starts to make a faint crackling noise. As the bloom “falls”, it becomes flat, and then cracks begin to appear into the surface, and eventually it falls past flat and becomes a little bit concave. (When it’s flat and starting to crack it looks to me a little bit like a chocolate cookie. It makes me hungry in the morning.)
That’s what I’ve noticed so far about the “phases” of the bloom. At which point in the process is it best to begin the rest of the pour?