If a 49mm filter with the same capacity as the current 58mm models produced better coffee, as Warrior says, why aren't the heavy hitters in the commercial machine market rushing to convert? The first maker to honestly say that they've converted to smaller portafilters for the sake of better coffee would have a huge advantage over the competition.
This would be so easy to demonstrate at trade shows, and the truth would be out there for all to see! I can just see it, company Zee brings out their 49mm portafilter machine and the buzz starts; "Have you been over to Zee's display yet? Their new machine uses 49mm portafilters and it makes the best coffee you've ever had!" All of a sudden the other machine makers would have power failures at their displays and couldn't demo their products.
The simple answer is the 58mm must be the best size or it wouldn't be so widely used.
If you had a wide variety of different lever espresso machines in front of you, you would notice several differences between each brand. One thing that you might notice, that they pretty much all have in common, is the height of their group head water chambers. Across the board, whether we are talking about home lever machines or commercial lever machines, almost all of the machines would have a 4-4.5" chamber. The height and diameter of the chamber have a direct impact on how much water will fit into that chamber. Something that would be different among the many lever machines you have in front of you would be the diameter of the PF. Elektra = 49mm, Ponte Vecchio = 45mm, Conti = 58mm, Caramali = 58mm, La San Marco = 55mm. All of these PFs with a double basket in them will fit approximately 18g of ground coffee.
Now, if you have the same amount of coffee with varying amounts of water being pushed through those tamped 18g pucks what differences will you see? You would find that the water flowing through the more narrow PFs had to push it's way through more coffee to get into the cup.You would also find out that less water going through will result in shorter shots, anywhere from .75-1oz. As a result of the previous two occurring, you would find that the machines with more narrow / taller PFs, and subsequently a more narrow water chamber, rendered shots with slightly more body and more layers of flavor. I think this has a lot to do with the design rationale behind most commercial espresso machine manufacturers PF size. They get a pretty darn good extraction and a 1.5oz volume in the cup. That is good for business.
Okay, now visualize something for me. Pretend you have 2 portafilters in front of you, a 58mm La Marzocco PF and a 55mm La San Marco PF from a lever. Now fill them both with 18g of coffee and tamp. The 58mm PF will have a wider / flatter puck to the La San Marcos more narrow / taller puck. The resultant shot volume will be slightly different with the 58mm LM producing 1.5oz and the La San Marco producing just under 1.5oz. So why does the shot taste different? Picture the water going through the coffee in individual droplets. Each drop of water going through the 55mm La San Marco PF will touch more coffee grounds and extract more of the essential oils compared to the water going through the the flatter / wider 58mm LM PF. The resultant product has a more vibrant flavor that presents itself in many more layers with slightly more body, due to the smaller volume of water, when compared to the shot pulled through the 58mm LM PF. It seems rather simple to me, the more layers of coffee you go through, the more you can extract from those grounds. I am not saying the 58mm La Marzocco is pulling garbage, I know they can pull amazing shots, but the end results are dramatically different.
James Freeman at Blue Bottle swears by 55mm La San Marcos. He is simply obsessed with them for pulling SO espresso shots, and that is all he uses them for in his shops. The Lux Coffee Bar in Phoenix, AZ uses a 3 group La San Marco Lever espresso machine as their primary machine in their shop. Tom Owens of SweetMarias says the 2 San Marco Lever espresso machines he owned were 2 of the best machines he ever had. An individual within Home-Barista, who has also restored a 1970s La San Marco Lever, utilizes his La San Marco Lever and a Synesso in his shop. He too states that he much prefers the shots from the La San Marco to the Synesso (although he did say he likes the temp stability of the Synesso when serving customers in a crowded cafe). These things have a cult following, and most of the people who have tasted prime shots from them become believers.
I think most people are scared of what they do not know, and levers are definitely not the norm. Most people who own coffee shots have never encountered, or care to encounter, a commercial lever espresso machine. I think all but the best coffee shops probably have way to high of an employee turnaround rate to take to time to teach someone proper technique machines that are much more finicky than a standard semi-auto.
I do have to say that I do not agree with the comment stating that most companies must use 58mm PFs because they are better. The reason I disagree is I have 2 machines in my house that could change everyone in this forums mind. I have never believed that the most widely accepted anything is ever the best simply because it is more commonplace. If you trace the PF size of almost all of these companies back to their early beginnings, you will find that their PF sizes have not changed. They probably do not see the majority of coffee consumers worldwide really caring all too much about the minor intricacies that a slightly more narrow / taller PF would add to the final cup. Let's be honest. . . . most people probably wouldn't.
Another thing most consumers probably would not like is a new and improved better tasting shot with a new volume of 1oz, per a 49mm lever setup, as compared to 1.5oz, from a 58mm lever setup. 98% of consumers would not be able to tell any difference outside of the increased cost per ounce of espresso. Not to mention if you reduce the amount of espresso you will also have to reduce the amount of water when making an Americano, milk when making a Latte and Foam when making a Capp, which means smaller drinks around the board. That probably would not fly!
I am sure even your mind could be changed, once you come over to the dark side Tex
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