Extraction & Dosing

A haven dedicated to manual espresso machine aficionados.

#1: Post by cazalot »

I'm about a week in with my Cremina and loving the journey so far. This is my first machine and I'm still very much learning the ropes. and this forum has been a great help. I'm getting everything dialed in and was hoping for a little guidance.

I'm shooting for a 1:2 extraction but so far haven't been able to get there. Currently I'm using 14 g espresso and consistently end up with 37 - 40 g out, which puts me at 2.5 - 3 x. My technique has more or less settled by now. I do a 10 second preinfusion, at which point I generally start to see the first drops of espresso hit the cup. After that my pulls take 30 - 40 seconds. I haven't gotten the bathroom scale out yet but force to pull the lever seems about right - I'm definitely putting in some force but I can comfortably manage with one arm without putting any body weight into it. I pull the cup out when the lever bottoms out, by which point the stream has generally slowed to a drip, but I typically end up with a decent amount running into my drip tray afterwards.

I've tried a few different things to troubleshoot so far. I'm using a naked portafilter and am seeing some donuting, channeling and spurting (a topic for another day). I've looked at a few ways to distribute - most recently I've been grinding straight in the portafilter, breaking up any clumps with a safety pin, and then giving it 3 good taps with the heel of my hand right before tamping. I'm grinding with a Specialita and have tried a range of grind sizes - everything from very fine, choking down the machine all the way to coarse which just flow right through.

I'm not sure what direction to look next. I was thinking a grinder alignment can't hurt. I've also noticed that the end of the shot tends to get a little more watery, but the idea of pulling the cup before bottoming out goes against my gut and everything I've read. I've been leaving the lever all the way up (valve open) during preinfusion. Should I push it down just enough to close the valve, so more water doesn't flow in during preinfusion? Or is it as simple as increasing my dose (although everything I can find recommends 14 g). I'm a little stuck here as far as next steps.

Taking a step back, I was also wondering more generally about dosing on a lever machine. How is extraction ratio adjusted for a given coffee dose? On pump machines it seems straightforward (stop the pump later or earlier) but on piston machines the piston has a fixed stroke volume (+/- preinfusion). Assuming the machine is used to full stroke, It would seem that the mass of coffee would be the only way to adjust ratio. Am I missing something?


#2: Post by ojt »

Quite simply just pull the cup off, and put another receiver in its place. That's how you control the ratio :)

When pulling longer than 1:2 it might get trickier, at least on my Pavoni. There, like you said, you'd dose less coffee. Also you can prewet the puck really well and do many other hoops and tricks but usually the 40g mark is pretty much the maximum. I've also dosed as little as 11g in the double basket and it still works really well, pulled a very nice 1:3 shot like that.

Dosing too much in my experience is not a good idea, but I can't really put my finger on the "why". There has been some talk about it (and research even IIRC) that the coffee bed gets too thick and you'd get uneven extraction. I stick to the double basket, even if I have the 20g triple also.

As for the channeling, my suggestion is just light WDT, no taps on the side (only down on the tamp mat / surface if anything) and a good single tamp. Also you could try cutting a disc of coffee filter paper and place on top of the coffee bed, might help with any potential strong water jets from between the inlet hole and the piston.

Edit: forgot to mention, for WDT the pin size matters. Go as thin as you can and I found more success with more than one pin. My current tool has 4 pins.

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#3: Post by drgary »

Sorry for the brief response. My first suggestion would be to weigh the shot output and pull the cup when you've reached your desired weight as described just above. Once you've got that down and see the level in the cup reached by that weight you can eyeball it. You'll want to grind to a level of fineness the shot will run about 25 seconds after you've finished preinfusion.

What I WOULD do for a good cup of coffee!