I am stumped by something. About a week ago, I watched someone pulling shots from a Kees Mirage lever machine in Scotland. In order to pull single shots, he pulled the cup out from under the group about halfway through the extraction. A single stroke of the lever with normal pre-infusion produced a full double.

A couple of months ago, I was in a bar in Rome watching the baristas pulling shots from a SM lever. A full stroke on their machine (with preinfusion) produced a classic Italian ristretto - about half the volume of the output from the Mirage. I watched several shots on both machines and this was consistent; the SM in Rome produced ristrettos, the Mirage produced doubles.

Is there a logical explanation for this?

Jim

Yes. In order to pull a true single shot, the grind and dose, not to mention the filter basket, have to be set up for pulling singles. In non-Italian shops, doubles are the norm. So, rather than have a separate (and infrequently used) grinder for singles, they just give you the first half of a shot.

Because the first half of a shot extracts differently from the second half, you are likely to get an extra-dense, unbalanced shot with this method.

If they don't have a single shot basket, they also sometimes use a portafilter with a double spout and then just let one stream go into the drip tray. That's generally a better method for pulling a single shot than cutting the shot half way through (as mentioned above, you can end up with overly concentrated flavors that are a little out of balance).

Ray

RayJohns wrote:If they don't have a single shot basket, they also sometimes use a portafilter with a double spout and then just let one stream go into the drip tray.

Yes. Ray is correct. The twin spout method is much more common than the "first-half" method.

According to the OP, these are lever machines. The per-stroke volume is therefore fixed by the machine. To increase the volume requires multiple pulls. To decrease the volume, you need to cut (or split) the pour.

Apparently one stroke produces a double shot volume (~50ml) on the Mirage. There is no way of knowing how much weight (or mass) this represents, but let's assume it produces a normale brew ratio for a double shot.

So, to produce a single shot on the Mirage: use a single basket, adjusting grind and dose for ~25 second extraction, and cut the shot (by pulling the cup from under the group) when it blonds. This is SOP for all extractions, and does not imply underextraction. On a pump machine you can turn off the pump, but not on a spring lever. You have to pull the cup.

If it's too much trouble to adjust grind and dose for a single basket, then splitting a double pour (dumping half the shot) should work. (This has always seemed an unconscionable waste to me. )

Hi Marshall, John, Ray,

I understand the dynamics of the lever group and why a single can be created by taking the first half of a double shot. What I can't understand is the bar in Rome. The baristas pulled the lever to the bottom, let it preinfuse, released the lever and let it rise through the full stroke. The output was a single ristretto. They were working pretty fast, without time for pulling cups out from under the stream and often without pulling coffee through a double spout. I watched them working for about 15 minutes while I sipped my cup.

The consensus seems to be that a standard (eg Rossi) commercial lever group has a volume around 50-60ml. That would make the Mirage typical. The odd part of this is the machine in Rome. That's what has me wondering if there is a way to modify a commercial lever group to reduce the water volume.

Jim

You are comparing the single stroke volume of two commercial lever machines from different manufacturers, presumably using different coffees, grinds, doses, etc. Volume is a notoriously poor measure for espresso extractions. If the Mirage pour had loads of crema and the SM did not, you might be observing similar extraction weights. And despite consensus, are you sure that the volume of liquid generated by a single lever pull is the same on the different machines?

Nothing wrong with speculation, but it would be nice to have some hard facts to work with...

Based on my experience with a commercial lever - Spanish gaggia.

The standard shot volume seems to be 25-30ml, with preinfusion of around 10s, with beading observed around the edges of a bottomless pf before releasing the lever.

To pull ristrettos I increase the dose, and preinfuse for 3-5 seconds, the puck doesn't reach full saturation and part of the stroke is 'held up' in saturating the puck which results in a shot of reduced volume.

To pull a normale I use a sort of Fellini move where I use spring pressure to pump the puck to full saturation, before letting the lever rise for a shot of greater volume,

hope I'm not stating the obvious here, but those are my findings - preinfusion matters.

I've enjoyed this thread, as a newbie with fond memories of Italian bars and who just recently bought a little lever machine.

I think the OP got his answer - that the lever machine volume is what it is, and can be adjusted a little with pre-infusion tweaks.

But I'd like to add some info/links that address that "wasted shot" when pulling a single shot in an Italian bar. (videos courtesy of Napoli barista Carlo Grenci)

If you pause at 1:28 in this video



notice that the left container in the leftmost group is a not a serving cup. He has orders for 5 singles and is using 3 levers.

What does he do with that wasted shot? Is not on the video, but Carlo (who posts on Barista Exchange forums) clues us in:

"....... here nobody throws away anything , and this is even more true in the case of our magic nectar ! Once the coffee (espresso) has cooled down it is poured into a big glass bottle picked from the freezer, sugar is added (if desired; we normally do but it should be dosed carefully) and the mix is shaken as seen in my video. The shaking must be repeated during the whole day in order to avoid th solidification of the liquid in one block.
Shaking produces, on the contrary, a gas emulsion that turns the whole thing into a frozen-like crema.
We just call this delight: CAFFE FREDDO."

To see the them serving one of these up. see:

Great videos Homeburrero, the making of caffefreddo was new to me.
Where is this bar, by the way? Somewhere in Italy of course, Napoli?
Every leverfan ought to jump out for a pilgrimtour thereto
Cheers
Ulrikmo