I'm not sure about the other levers, but the la Pavoni grouphead holds about 1.5 oz in an outer chamber which then becomes the brew water for the next shot. At one time I toyed with the idea of drilling a hole through the grouphead into its outer chamber in order to place a thermocouple there. It wouldn't be great temperature control, but it would be better than what's already there...

Wow, just got done reading the last entries of the thread... What a thread...

Jarno wrote:I'm not sure about the other levers, but the la Pavoni grouphead holds about 1.5 oz in an outer chamber which then becomes the brew water for the next shot. At one time I toyed with the idea of drilling a hole through the grouphead into its outer chamber in order to place a thermocouple there. It wouldn't be great temperature control, but it would be better than what's already there...

Wow, just got done reading the last entries of the thread... What a thread...

Agree that this is a great thread.... I have to read it again, and again .... and again.

I didn't realize that the europiccola had a 1.5 oz outer chamber - does this mean it is an 'infused' or 'saturated' group? I thought that all the brew water was in the boiler and not until one pulls lever and exposes the 'hole' does one get brew water in the grouphead. I recall seeing a cutaway of a La Marzocco grouphead here cutaway-of-la-marzocco-saturated-grouphead-t700.html - is this what you mean? Is there a cutaway of the europiccola around?

Jarno wrote:I'm not sure about the other levers, but the la Pavoni grouphead holds about 1.5 oz in an outer chamber which then becomes the brew water for the next shot. At one time I toyed with the idea of drilling a hole through the grouphead into its outer chamber in order to place a thermocouple there. It wouldn't be great temperature control, but it would be better than what's already there...

Wow, just got done reading the last entries of the thread... What a thread...

Wouldn't having "an outer chamber which then becomes the brew water for the next shot" mean that if you shut the machine down for a while and then come back later you'd have to flush out from that "outer chamber" the now-too-cold water before pulling the first shot? I've not experienced the need to do that on my Pavoni-like Gaggia Factory...

(And, absolutely yes - great thread indeed!)

caeffe wrote:Agree that this is a great thread.... I have to read it again, and again .... and again.

I didn't realize that the europiccola had a 1.5 oz outer chamber - does this mean it is an 'infused' or 'saturated' group? I thought that all the brew water was in the boiler and not until one pulls lever and exposes the 'hole' does one get brew water in the grouphead. I recall seeing a cutaway of a La Marzocco grouphead here cutaway-of-la-marzocco-saturated-grouphead-t700.html - is this what you mean? Is there a cutaway of the europiccola around?

I'm not sure of the concept 'infused' vs 'saturated' for this particular model. When the brew water reaches the head, it is superheated and needs to cool down to brew temperature. Thus, the grouphead acts as a heatsink in this manner. However, the brew water does not recirculate with the boiler again. It is used for the next shot, so the temperature of the brew water is not stable and timing your shot is everything. I measure the temperature delta by placing a thermocouple on the grouphead surface and search for the optimum temperature there. I'd say the consistency shot to shot from this method is about 80%.

r-gordon-7 wrote:Wouldn't having "an outer chamber which then becomes the brew water for the next shot" mean that if you shut the machine down for a while and then come back later you'd have to flush out from that "outer chamber" the now-too-cold water before pulling the first shot? I've not experienced the need to do that on my Pavoni-like Gaggia Factory...

(And, absolutely yes - great thread indeed!)

When I first turn on the machine in the morning, I find my first shot, if I don't flush first, to be too cool. The espresso runs thin and the flavor is bright. The second shot is near perfect with good mouthfeel. The third shot is too hot/bitter and loss of mouthfeel. By the 4th shot, the lever jams. So my first blank shot is only about an ounce so that the next brew water is a mixture of hot and cool water and the final brew water is about right.

Just for more insight into the Pavoni grouphead, the entire head holds about 3 oz, as there is another 1.5 oz in the space above the piston. Therefore with each flush/pull, the grouphead is heated with 3 oz of superheated water, not 1.5 oz. When the lever is raised, the water above the piston is actually pushed back into the boiler (notice that the pressure gauge registers a drop due to a temporary drop in boiler temp) before the inlet hole is uncovered allowing the brew chamber to fill for the shot.

When I make my second espresso (after the blank shot and first espresso), I first proceed to cool the grouphead. I first turn the machine/boiler off. I have a lever rest which I use to hold the lever in the cocked position, but not open all the way. The purpose here is to evacuate the space above the piston. After all, why cool 3 oz of water when you can just cool 1.5 oz. Do the usual wet rag/ice cube bit. Then turn on the boiler and measure the grouphead surface temp to 127 to 135 deg F depending on coffee and ambient temperature, then brew. Repeat as often as needed. It takes me 10 minutes per cup.

Jarno-
I still don't quite follow this.
Are you saying that after the 1st shot/flush there is actually water in the grouphead amounting to about 1.5 oz? hence If I only pull 1 shot, and leave the machine there will be water in the grouphead? I thought that water didn't enter the grouphead until the lever/piston is raised past a certain point. This water is then pushed out through the puck by the barista pushing down on the lever. What would happen to the water in the grouphead if I turned off the machine?

Yes, there's about 1.5 oz of water that sits ABOVE the piston. That's why they recommend you do 2-3 "half" pumps on the FIRST shot. It's to push that water BACK into the boiler and pull some hot water back in. It warms the group up.

I usually do about 3 of the "half" pumps to warm the group for the first shot. Then I wait for the p-stat to finish cycling and then pull the first shot.

caeffe wrote:Jarno-
I still don't quite follow this.
Are you saying that after the 1st shot/flush there is actually water in the grouphead amounting to about 1.5 oz? hence If I only pull 1 shot, and leave the machine there will be water in the grouphead? I thought that water didn't enter the grouphead until the lever/piston is raised past a certain point. This water is then pushed out through the puck by the barista pushing down on the lever. What would happen to the water in the grouphead if I turned off the machine?

Hi Caesar,

There is always water in the grouphead. Even after the machine is off and cold, the water is still in the grouphead, held suspended by vacuum, as no air is allowed in the grouphead. I haven't yet found an accurate schematic of a Pavoni head (and I would draw one if I were any sort of artist), but if you remove the head from the boiler and then the tube from the grouphead, you will find that there is still water left in the head. Upon removing the piston (for cleaning) you will see that there is a nylon sleeve (millenium model) that the piston fits in. There are some pictures of this somewhere on this site. The top of the sleeve are 4 slits that allow in the boiler water above the piston. Also, there is space around the outside of the sleeve from which the inlet hole allows in fresh brew water. This space amounts to about 1.5 oz. And as noted, the piston may be pushed up and down and thus moving the water back and forth into the outer chamber of the grouphead and the boiler. The maximal space above the piston is also about 1.5 oz.