Tips for Extracting Espresso at Low Pressure

Beginner and pro baristas share tips and tricks.
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Postby Jake_G » Apr 17, 2019, 10:20 am


Life is a funny thing. It really is.

As mentioned elsewhere, I recently received a once-in-a-lifetime, too-good-to-be-true and otherwise generally amazing deal on an early GS/3 AV. This machine was assembled over the winter of 2007-08, and was living the good life, pulling shots later that year. It arrived at my doorstep some 11 years after final assembly and was in excellent condition, but it did need a few minor routine maintenance items, so I pulled it apart to change all the seals (and because I'm certifiably nutz, and enjoy dismembering my machines).

All of this is in preparation for the GS/3 to replace my current plumbed in, flow profiling commercial 2 group Rancilio S20 MIDI CD. Well, the S20 must have gotten jealous seeing all of my attention on this new machine, and on Saturday morning (or was it Friday?) the Procon pump seized up whilst back flushing after the last shot of the morning...

What to do?

•Steal the Fluid-O-Tech out of the GS/3?
That's an option that was considered, but I hate to turn the GS/3 into an organ donor when I'm trying to get it put back together sooner than later...

•Remove the Procon from the S20 and see if I can repair it?
Another solid option, but I'm really trying to focus my attention on getting the GS/3 back together. I dont multi-task very wel...

•Say "The heck with it!" and see if I can pull a decent shot at line pressure?
Image:Yellow Catuai from Brazil Pulled at Line Pressure

Ok, so "What about the Tips?", you ask...

Well, as mentioned above, the S20 is a profiler with a needle valve in the brew group, much like Bianca or the new Profitec option. So here's the workflow I have been trying lately with pretty solid results:
    •Set grind somewhat coarser than for "normal" profiled shots, but tighter than straight 9 bar shots.
    •Dose a half gram or so less than "normal".
    •Set water debit to 1.5-2ml/s and pre-brew until basket wets.
    •Open needle valve a lot (I can turn mine ~4.5 turns, lock to lock).
    •Taper flow off to emulate a lever profile.
    •Cut when flow goes translucent.

So far, the results of this approach have been surprisingly good. Better than with a pump? Maybe not, but the shots are balanced, decent and surprisingly "espresso-ish", which is a way better alternative than living without espresso while I sort out my issues. As it is now, I'm perfectly content living like this until the GS/3 is up and running and I can transfer bar duties over and work on getting the S20 ready for a new owner...


- Jake