“(Since the study published) I’ve been receiving a lot of emails from people telling me how grateful they are, because from just a cleanliness standpoint, this is a massive, massive upgrade,” Hendon said. “What I would recommend for the home user is to start with a single drop of water and build up from there — there is a substantial amount of nuance in this process.”
There’s also a catch: The water improves cleanliness regardless of your brewing method, but a brewing benefit only occurs with espresso and, to a lesser extent, filter coffee. When using a cafetiere, French press or AeroPress, nothing much changes because, given the coarser grind required with these, “all of the water is already touching all of the coffee,” Hendon said.
—from The secret to a perfect cup of coffee, according to science [archive]