LMSC Why do you need 10 brews for each coffee? You will have a sweet spot, which will be the starting point and can’t see you requiring more than 3-4 dials for a new bag.
For the dialed in brew, on an average, what is the typical under 400/500 % do you get?
I don’t do 10 brews with each coffee when testing. I do a couple of brews to get my aim in, then I do 10 brews , same parameters with 10 different coffees (1 per coffee) and look at the averages. That 10 may grow to 20, 50, 150 over time, but I don’t make any recommendation until I am reasonably confident that I can pick up a bag of coffee & make a representative brew in one live take.
We talk a lot about retention, dose consistency, consistency in general, the ability to switch from one coffee to another…if you are changing grind setting all the time you are not getting consistency. You are, of course, free to fine tune a coffee for a method, but to know if a particular set of parameters work it’s best to stick to them until you are driven to make a change, then repeat the process again.
The sweet spot, for me, is the point where the largest number of coffees produce representative brews at the same parameters.
The % of grinds under 400 or 500 depends on how fast/slow & how many pulses you pour the water.
The finest side of brews I make with a pouring kettle is 12% under 400/17% under 500.
The coarsest is 8-9% under 400, 12% under 500.
I’m sure there are plenty of points in between that will work for interim pour speeds.
Why do you think the extraction yield would be different, based on which grinds were on top? You’re still going to have the same mass with the same distribution.