Non reversible modifications to lever machines
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rpavlis
- Posts: 1799
- Joined: 12 years ago
Although my espresso machines are highly modified, I try to avoid making modifications that are not reversible. I retain parts that were modified even when they probably belong in the trash.
One of the most common irreversible modifications is to "chop" portafilters. I have always thought this to be an extremely BAD idea unless one had another unmodified portafilter available. Chopping a portafilter changes its thermal characteristics, and can do so a LOT. This morning I did a little experiment. I pulled two shots with a 2nd generation La Pavoni Europiccola, 1998. I used a ramekin to adjust the base of the group to 89C before each shot. I used bone china (Lenox Ming) demitasse cups because they are thin and have less thermal capacity than most other ones. Both cups were at room temperature, 21 degrees, when I started. I deliberately let the machine get too hot for the first shot, and cooled it with a Ramekin so both shots would be from the machine in as identical conditions as possible, with the 89 degree portafilter base.
The temperature of the bottomless shot immediately after pulling was 64.6. The temperature with the stock portafilter was 58.4. The stock portafilter without handle or spout weighs 188grams. That is about 3 moles of metal! (Metal specific heat is 3R per mole, where R is the gas constant. R=8.31 J/deg mol) Brass has rather high thermal conductivity, so it not only cools the espresso emerging from it, but it must also cool the group significantly.
No matter how careful one is, one occasionally gets mists of espresso from bottomless portafilters. In fact applying pressure suddenly is apt to cause tiny droplets to form even with well packed shots because there is no liquid under the emerging espresso when it first emerges. With a bare metal machine like real copper La Pavonis, this quickly makes the boiler have tiny black spots on it. In the course of making dozens of shots one is likely to have a less than perfectly tamped shot that will also be a spurter. I always put a piece of high temperature plastic sheet between the portafilter and the boiler when using the bottomless.
The trouble with chopping the stock portafilter is that after chopping it, one has no choice unless one had a spare one!
To me the sensible thing is to purchase a bottomless one, or else find a discarded one so that one still has the stock one.
If one change steam tips it is a bad idea to discard the original because different tips work best for different purposes.
One of the most common irreversible modifications is to "chop" portafilters. I have always thought this to be an extremely BAD idea unless one had another unmodified portafilter available. Chopping a portafilter changes its thermal characteristics, and can do so a LOT. This morning I did a little experiment. I pulled two shots with a 2nd generation La Pavoni Europiccola, 1998. I used a ramekin to adjust the base of the group to 89C before each shot. I used bone china (Lenox Ming) demitasse cups because they are thin and have less thermal capacity than most other ones. Both cups were at room temperature, 21 degrees, when I started. I deliberately let the machine get too hot for the first shot, and cooled it with a Ramekin so both shots would be from the machine in as identical conditions as possible, with the 89 degree portafilter base.
The temperature of the bottomless shot immediately after pulling was 64.6. The temperature with the stock portafilter was 58.4. The stock portafilter without handle or spout weighs 188grams. That is about 3 moles of metal! (Metal specific heat is 3R per mole, where R is the gas constant. R=8.31 J/deg mol) Brass has rather high thermal conductivity, so it not only cools the espresso emerging from it, but it must also cool the group significantly.
No matter how careful one is, one occasionally gets mists of espresso from bottomless portafilters. In fact applying pressure suddenly is apt to cause tiny droplets to form even with well packed shots because there is no liquid under the emerging espresso when it first emerges. With a bare metal machine like real copper La Pavonis, this quickly makes the boiler have tiny black spots on it. In the course of making dozens of shots one is likely to have a less than perfectly tamped shot that will also be a spurter. I always put a piece of high temperature plastic sheet between the portafilter and the boiler when using the bottomless.
The trouble with chopping the stock portafilter is that after chopping it, one has no choice unless one had a spare one!
To me the sensible thing is to purchase a bottomless one, or else find a discarded one so that one still has the stock one.
If one change steam tips it is a bad idea to discard the original because different tips work best for different purposes.
