Hey out there! I know this question sounds pretty stupid, but when do I actually start measuring the time while making an espresso? The moment I click on the button or when to coffee starts to drip?
Would be awesome if somebody could help me, because I’m going through a lot of awesome posts from Matt, but he didn’t mention it anywhere. 
I think the generally accepted rule is to start the timer when you start the shot. Just because you aren’t seeing the espresso come out immediately (hopefully) doesn’t mean the water hasn’t begun to infuse with the espresso. You may as well be timing the whole process, not just what you can see.
Another reason to start them together is to measure whather the shot is coming out “on time”. Where I work we want the shot to start dripping out at around 6s and if its much before or after that we can already begin to assume it will likely not be up to our standards. Of course you should always be weighing your shots to measure quality and standards but if the Acaia’s charging on the other counter this can help to QC for a shot or two.
…like @JJC, I think it’s best to start the timer in conjunction with the pump. I don’t know what set-up you’re using, but there could be an entirely separate discussion with respect to timing if you were using a machine capable of pre-infusion (there’s lots on BH about this…).
With espresso, taste wins every time! You can manipulate your grind and dose to get just about any volume you’d like in ~30 secs so time is the least important of these variables and assuming that the distribution, tamp, water temp., etc. are all 100% consistent and repeated with every shot (PS…they’re not!).
Regards,
S.
I third the above opinions. I do measure both times simultaneously, but conventional shot time starts at infusion pressure.