If you search YouTube for V60 brewing videos and guides you’ll find about three billion different ones. Some with agitation, some without; pouring fast, in the middle, making circles; 40-60 or 30-70 or whatnot.
I always think to myself that they’re mostly just fluff.
It all depends on grind size and temperature. Doesn’t matter how you pour (well, within limits I would think) as long as you get your temps and grind right for the pouring technique you’ve chosen.
Admittedly, I haven’t tried a ton of different ones, maybe three or four. But this is the feeling what I’ve got.
Maybe there are some edge cases, like Ethiopian coffees being more prone to clogging the filter so less agitation might be a good idea.
What’s the 40-60 ratio?
It’s referring to a process called the 4:6 method invented by Tetsu Kasuya.
https://youtu.be/wmCW8xSWGZY?si=CTSasTW9N9iiTTXy
Basically that after blooming with small amounts of water you pour 40% of your entire brew size, wait, and pour the remaining 60%.
Some people say that the first pour determines how sweet the coffee is and yeah, I have a hard time believing it.
Probably seconds. 40 second bloom, pause, 60 second something else. Just a guess.