#22: Post by gscace » 9 minutes ago

Hi:

I use a one-group La Marzocco Leva X. The Leva X has 6 lever engagement notches in it’s cam so that one can select from 6 different piston swept volumes (brew volumes). I normally use the third notch, which produces a 42 gram shot when used as described below. Spring tension can be adjusted to change max brewing pressure. Mine is set to 10.5 bars when used at the third notch. I don’t know if that’s the most perfect setting. I just set it there and it works. The Leva X can be plumbed into a water supply or used with an integrated water reservoir. I use the integrated reservoir because my machine is near my roaster in the basement and I haven’t built an actual bar with a sink and dedicated water supply. I feed it water from an Everpure EZ-RO system, which adds Calcium carbonate back at around 50 ppm. A rotary vane pump sets preinfusion maximum pressure to 3-bars. It’s adjustable, but I think 3 bars is about right. I use a bottomless portafilter so that i can observe preinfusion, and because it’s cleaner than spouts and i don’t divide shots. I use IMS competition basket B702TCh28.5E, which is a convex basket. I use this basket because in my testing it produces consistently high extraction yields. The convex bottom adds more coffee to the center of the cake, which gets better water flow than the perimeter. I do not use any additional screens or filters. My go-to dose is 20.5 gms and I find that this works for most everything in the end. For grinders I use a La Marzocco Swan conical, or Weber EG-1 with the core burrset. But nearly all of my coffee is brewed with the Swan, which lately I’ve been using as a single dose grinder.

My Leva-X is adjusted to produce 93 Deg C brewing water. The shower screen in the Leva-X sticks down a mm or so further than most machines, so I had to build a custom Scace device for it. Using it and the WBC temperature measurement protocol, I learned that the machinery sitting on top of the group absorbs some heat, so the machine likes about 7 seconds of flushing if it has been sitting idle for more than 5 minutes. Then it’s remarkably reproducible. Brewing temperature reproducibility is about 0.5 Degrees C over all duty cycles tested in the WBC method, and the shape of the profile is remarkably consistent - a declining profile that is unusual for nearly all espresso machines i’ve every tested.

Having exhausted my blathering about machine setup, my technique is to flush the group for 7 seconds, when I get ready to pull the first shot, or a walkup shot. I engage the appropriate notch (3), pull the lever down to lift the piston and engage 3 bar preinfusion. After shoving the cup underneath, I observe the bottom of the filter basket and preinfuse until I see coffee on the bottom of the basket, indicated that the coffee cake is saturated with water. That takes around 10 to 15 seconds depending on the coffee. Then I ease up on the handle and let the spring take over. I don’t try to finess the pressure ramp. I just don’t slam on all of the pressure. I brew pretty long extraction times. Most coffees roasted the way I do it seem to like total time (preinfusion and brewing) in the 45 to 50 second range. Sometimes when I’m dialing in a new coffee I’ll accidentally get one over a minute. They’re still drinkable. A long time ago I quit worrying about the so-called 25 second thing.

-Greg

My brewing practice is to