I'm curious to learn the differences between the La Pavoni and Cremina lever groups. This is further complicated because there are multiple versions of each. They seem similar on the surface but I know that there are difference (some that seem minor and some that aren't minor).

I know that there are differences in boilers, cases, boiler temperature management, etc. but I understand those pretty well and there are tweaks/practices that can be used to deal with their characteristics.

What are the pros and cons of each group and the different versions? Which group is preferred and why?

Groups need to have provisions to keep them well above room temperature because without such provisions the espresso produced would be cooled off too much by heat transfer from the brew water to the group.

Groups are heated by: (1) direct conduction from the boiler to the group. The thickness, shape, and metal used to make the group results in variation of just how much heat is transferred this way. (2) Heat lost from the brew water of the previous shot to the group. (3) Possible provisions to heat the group by bringing in extra hot water or steam. (There may be other methods, but these are the common ones and the ones used in the machines under discussion here.)

The 1961-1973 La Pavoni groups have a piston that runs inside a brass sleeve. Each time the group handle is raised, the water in the space between the sleeve and the group wall and above the piston is mostly forced back into the boiler. When it is lowered again hot water, about 115 degrees, comes into these spaces and heats it--it also flows into the space below the piston. A user can raise the group temperature by moving the handle up and down several times without raising it high enough to release water and steam.

The 2001 to present La Pavoni groups have a similar (cheaper to manufacture of course) system except the sleeve is made of polyphenylsulphide.

The 1974 to 2000 groups have no brass or plastic sleeve. Instead there is a passage that delivers hot steam from the boiler to the top of the group. Once the system is bled of air, the top of the group, because of the laws of chemistry and physics, remains at the boiler temperature as long as the machine is running. This is good for those making one or two cups of espresso, maybe even best, but because the group top is always hot, the group can (and does) become seriously overheated after a while resulting in bitter espresso that is boiling as it emerges from the portafilter.

The Cremina has a passage somewhat the like the 1974-2000 La Pavoni systems. However it delivers not steam but hot boiler water (from the lower part of the boiler) to the group. Water is essentially incompressible, so that hot water only enters the space above the group piston when the handle is being lowered. If one make many shots quickly this system can obviously produce overheating. It is important to remember that this water is expelled back into the boiler as the handle is raised, and new heated water enters as the handle is lowered.

I have always wondered why no one ever reported connecting a tube from the boiler side of the steam hole of the 1974-2000 La Pavonis to make them act like Creminas. I probably would have done this were it not for the fact that I almost never have occasion to make more than one or two cups. (And when I do I use my museum like 1964 La Pavoni or my MCAL.)

Thank you, Robert, for your excellent explanation.

I have a La Pavoni Millennium machine set up side by side with a 1987 Cremina. They perform very similarly. I go for the same target outside group temperatures on each when pulling a shot. The Pavoni can get a spongy feel on the pull even if I flush it first. But the espresso is very similar and I can get both to be consistent. The La Pavoni accommodates a somewhat higher dose because it takes a wider filter basket (51mm instead of 49mm) even when I'm using an Elektra double basket in the Cremina. Because I'm measuring outside group temp with a thermometer I can pull multiple and consistent back-to-back shots and was able to do this with the second generation La Pavoni groups by toggling power on and off and inserting a cooled portafilter. I will soon have a first-generation La Pavoni to compare. That restoration is underway.

I use a different type of home lever (Ponte Vecchio/Sama), but had a Pavoni on loan for a while. The Cremina and Pavoni groups looks similar, and I always assumed it acted similar, as Gary wrote.

I see the problem in the opposite light as rpavilis described, that is, it's more difficult to keep the group sufficiently cool than it is to get it warm. I found that once the Pavoni got up to boiler pressure the group was plenty hot to prevent over-cooling the water, and that it tended to under-cool it (i.e. brew too hot). But I think I had the pressure set up a little over 1 bar, and most people probably keep theirs a little cooler.

Most home levers require some form of temperature management in any case, and by all reports both the Cremina and Pavoni are easily managed with some attention to detail.

There are serious espresso machine design problems. People who want a fast cup of espresso without waiting a long time for the machine to warm up have problems getting the system warm enough for the first cup. When systems provide enough heat transfer to the group to get it up to temperature quickly, that heat transfer, if it continue, results in over heating. This continuing heat transfer is the biggest problem with the 1974-2000 group!

The beauty of the Cremina, 1960 to 1973 La Pavoni, and the 2001 to date La Pavoni is that the design brings in extra hot water into a space in the group with each pull to keep the group warm. By pumping the handles on these machine boiler water can be pumped in and out of the boiler to provide more heat. I can get my 1964 group hot enough for the first cup faster than the 1999 one. It does not overheat because the top of the group is not constantly at 115 degrees! The amount of space outside the sleeve in the sleeved La Pavonis obvious makes a lot of difference in how these machines function.

Ambient temperature and altitude are important to ALL of these machines. Above about 3000 metres one gets to the point where it is difficult to get a sufficiently high brew temperature.

When systems provide enough heat transfer to the group to get it up to temperature quickly, that heat transfer, if it continue, results in over heating. This continuing heat transfer is the biggest problem with the 1974-2000 group!

I guess I had one of these on loan, because it heated up quickly but then became too hot. When I finally get a new Pavoni I'll look for one of the older ones - they sound like the best.

With the Ponte Vecchios I can easily be up to brew temperature in 10 minutes simply by pulling some hot water through through the group as soon as the machine is up to pressure. I don't use group thermometers, but just go by the "ouch" technique. If I pull 1-2 oz through the group it quickly becomes warm enough to pull shots.

There are some interesting design differences between the Pavoni/Cremina groups and the Sama/PV groups (aside from the spring, but probably related to it). Both groups are taller and narrower than are the Pavoni groups, presumably to accommodate enough travel for the piston, and to keep the diameter small enough to create proper brew pressure. The result in regards to heat management is a more effective heat sink (greater mass and higher surface-volume ratio). The PV group virtually never even attains 90 C at pressure less than 1 bar.

The Export group is a simple dipper into the boiler and is heated by brew water and its direct connection to the boiler. The Lusso group has the same shape, but is connected only by a thermosyphon loop the boiler. The Export is a little more variable in temperature and one needs to monitor it more carefully for proper brew temps. The Lusso thermosyphon functions very well, and it's always at the correct temperature when idle, and recovers more quickly for multiple shots.

PC

drgary wrote:The La Pavoni [millennium model] accommodates a somewhat higher dose because it takes a wider filter basket (51mm instead of 49mm).... I will soon have a first-generation La Pavoni to compare. That restoration is underway.

I was wondering if the first-generation LPs take the same size filter baskets as the third-generation ones (51mm).

Matt

I found this cutaway diagram of a Cremina group.
Olympia Cremina 2002: The evolution of design

Here's a cutaway of a Pavoni Millennium group.
http://www.linz.wright.name/pavoni/Pavo ... ection.png

mathof wrote:I was wondering if the first-generation LPs take the same size filter baskets as the third-generation ones (51mm).

Matt

No. First generation are 49mm. The portafilters are deeper, but you would need a correspondingly deeper filter basket to exceed an Elektra double basket. Although I have one of the old groups my machine did not come with the original double basket. An Elektra double fits well in the portafilter without mods. (I wouldn't modify that portafilter anyway because it's a very collectible machine.)