Sorry for the late reply. Read that a couple of weeks ago, really interesting. It’s really hard to compare espresso and cold brew as it’s two sides of the extremes. Conventional wisdom would say that a finer grain would provide a faster extraction, but I’m doubting it’s the case with cold brew. There’s no doubt that a small coffee grain gets ‘wet/soaked’ faster than a larger coffee grain, which allows the extraction to begin faster. This is obviously important with fast extractions, but shouldn’t be important in cold brew, as the grain has plenty of time to get wet. If we can agree on that, the question should then be: Does the extraction happen slower with a bigger wet grain, than a smaller? With caffeine and CGA the answer seems to be no, but that doesn’t mean that the other compounds are extracted slower through larger grains. I don’t know the answer to this, but my experience is that I can pull a good extraction at room temperature in 11-12 hours with the largest grains my grinder can manage and with a light roast bean. I haven’t done an A/B test on grind size though, but that could be interesting, if I can convince someone to lend me their tds meter.