Thank you
@dfk41,
@The Systemic Kid &
@Stevebee for replying. Helps to get a better understanding of this, and I very much appreciate your knowledge & advice.?
Yes, gulp, I do preinfuse longer than most ?... and my timing is determined by the degree of coffee sweat I can see on the screen, but that can take ~20 seconds.
I have played with preinfusing with the lever down and with it up. I get the sweetest, best tasting, shots with a finer grind & a longer preinfusion, & long enough to completely saturate the puck. (No bitterness.)
L1 directions leave the lever down for 3 to 6 seconds, release & pull the shot. In my case, the puck is not fully saturated when the lever is down for 10 or even 15 seconds; visually it appears to be only partially wet, in that the screen is darkening just a bit with coffee from behind, but no sweat shows on the face of the screen; whereas, if I let the lever stay down for a short 3 or 4 seconds, then slowly raise the lever until I just reach the catch point, an even sweat starts to break across the screen, and then I wait until thick droplets form, then release, the shot really is divine. (I have tried grinding at coarser settings, but the shot is not as good.) And, if I release the lever before the sweat starts to form a thick droplet or two, I also don't feel the shot is as good.
As an experiment, I left a used coffee puck in the portafilter after pulling a shot, and then tried pulling numerous shots with it, one right after the other (used puck left in there), preinfusing for 3 or 6 seconds in the lever down position, and releasing fully. No stalls, no machine stopping dead in its tracks.
So, these long preinfusions of mine (esp. with lever in upper catch position) definitely mess up the system with air, and then the L1 stops dead. I can't figure out how to get rid of that air, fully, in between my shots. Perhaps there is no workable way to do so? ? I have tried getting rid of the air by running the hot water tap, releasing steam from the wand, flushing the grouphead, tried a quick flush, and also a long full pull flush. (The one thing I haven't tried is pulling a second shot into the just used portafilter-maybe a second pull after the shot would release air, before unlocking???♀)
And, what happens to that air bubble while the machine is off for a couple of hours? Does it just shift out of the way temporarily to a place in the boiler where it doesn't cause trouble, or has it completely dissipated during the cool down of the machine when it is turned off? I had also wondered if the heat build up accumulated in the machine, when it is on & sitting idle for several hours, could be a factor??