Here is my latest report to Sean at Caffe Lusso. I'd be interested if anyone may have a solution to my uneven extraction problems?

See below:

I keep working to dial in GMC on my machine. I'm still having difficulty. My main problem is that I can't get a nice, even extraction, no matter how much care I put into puck preparation. The flow I get from the bottomless pf is always somewhat uneven, often channels, and the resulting flow is thin, almost watery, and clings to the bottom of the basket (as opposed to flowing out in a nice cone).

This is despite stirring the grounds to break up clumps, distributing evenly in the basket, and tamping evenly with a level of care that even exceeds what I usually put in with other blends or s.o. beans, and from which I'm used to nice, even extraction as the norm.

It has been a while since I had last pulled GMC, but I don't recall it having been fickle at all.

Right now, the resulting beverage doesn't have an offensive taste per second, but it has very little body or viscosity, and none of the velvety feel I recall from past experience with GMC.

Have you sometimes seen this phenomenon, and if so would you have any suggestions for a fix?

I'm currently putting 17 g in an 18g VST (to ensure that interference from the screen isn't the cause of the channeling) and get 27g out in 25-27 secs at around 203 F, albeit with some channeling and unevenness as described above.

Another update:


In a last gasp effort, I tried taking my grinder to unchartered territory, to a grind setting 5 notches coarser than I typically use for espresso (usually, half a notch to a notch in either direction is a substantial change...) and upping the dose considerably.

22g in my 21g basket with that super coarse setting gives me a bit too fast a shot, but the extraction at least seems much more even, and the taste isn't offensive. I think I'll give myself more time to fine tune that setting.

It may just be that this coffee on my grinder requires a level of grind and a dose I had simply never had to work with before. That seems pretty far off what seemed to be most reviewer's receipe but maybe my equipment and this batch of that blend require it...?

If you aren't getting body with GMC I would go back to the basics with your decent.

18g in 36g in 25 seconds at 8-9. I personally prefer 8.

If the beans are fresh a 36gram yield should fill up a demitasse completely, which at least a centimeter being crema. The crema should dissipate a decent amount as the shot sits, because it is really quite a gassy bean. This is what gives it a lot of the body and mouthfeel. It's one of the few gasy blends that I like, because most of them end tasting like asprin.

If using those parameters doesn't net you a shot with lots of body, the beans might have out gassed too much or aren't fresh, or there is something going on with your pressure and flow such that the oils and lipids aren't emulsifying and the co2 gas is somehow escaping the beverage some other way. A long shot can do that, so I personally would save those long extractions for light roasts if you are chasing a mouthfeel shot.