Adam Ward wrote:worry about all the empty space above the puck causing issues between pulls.

I finally understand that your requirement for good espresso is to use Fellini technique with multiple pulls and would like the expanded puck to push up against the shower screen so it doesn't get disturbed when pulling a second or third time. Most people have some headspace so that the puck doesn't push up against the shower screen. Most people don't use Fellini (pump and larger volume spring levers). This makes your view of espresso extraction unique and difficult for the rest of us to follow.

Exactly! The pressed espresso puck acts like a sponge...and all the tamp pressure in the world won't protect its continuity in an open condition, with head space. It is imperative to preinfuse and steep properly. Proper pressure is simply required to release the carbon dioxide and emulsify the best oils during the initial extraction. Creme can be gross if it's primarily extracted towards the end of a shot because it carries undesirable elements from the woody parts of the substrate...as opposed to the signature buttery results from a proper creme or emulsification. This extraction process and religion as far as I'm concerned lol, can only be accomplished on very specific machine designs on any consistent basis. Imho. Thanks for sticking with me till we understood each other...I'm sure that took patience

Well, I should clarify...where most people probably feel that a Fellini maneuver is simply done because of limited group head water in a smaller lever machine, I feel a shot has 3 stages: pre infusion/steeping, primary pull and a steady, lighter finish pull to get the rest. After a primary pull there should be a short pause in action anyway...to steep a second time...it's just the right thing to do when extracting nearly any plant material really, so that pause is a good time to grab more water with a lever.

I'm struggling to understand how Fellini could ever be done without disturbing the puck, regardless of amount of headspace, and why a Fellini is somehow critical to emulsification of oils and water to make crema.

Because you have to preinfuse with the first pull. The puck expands when it is preinfused....that's what pressurizes the puck, which is needed to creme. If your machine design considers head space above the puck. So yeah, if your shot water is pumped in through a dispersion block right above the screen like normal, then all the pumps on the lever won't disturb a thing. Some designs definitely do disturb the puck while moving the lever for sure.

7 pages and I still don't t understand what you're getting at.
The spring or muscle generates a force.For pressure to exist at the other side of the force resisistance is needed. That is provided by the puck.I don't t need preinfusion to create crema.If I pull the lever down and put it back up right away without any preinfusion pressure is there and I do have rich crema.
Probably more channeling but that is normal .
If a Fellini move disturbed tge puck depends on the barista.If you have a feel for your machine you can let water enter the chamber very gently so there hardly will be any disturbance.

Some machines pour water on the puck from a port that gets exposed when the lever is all the way up...like the Pavoni. It's hard to visualize, but even a tightly packed puck can fall apart under water pressure...even if the water is pressurized in the space above the puck. The grinds can still float up into that pressurized water...the grinds don't know that water is pressurized, the only pressure recognized in that condition is somewhere in the puck at the point the water faces resistance as it travels down through it. The head space area, apart from the initial pull, feels no pressure at all throughout the pull. You can get lots of creme, but without pressure you can't get good emulsification. That's why a typical design depends greatly on "constant pressure" to succeed. If you have a design that allows the puck to physically pack the space tightly...and also puts the shot water directly into the dispersion block...you can Fellini and adjust the lever pressure till your hearts content and it won't disrupt the puck.

Yeah that is my take as well. I'm also still unconvinced that the process as described won't disturb the puck. There's some suction upward on those Fellinis, even assuming they are done gently as others have mentioned and regardless of headspace or lack thereof.

I will also acknowledge that I've never been drawn to the side of espresso that centers on extreme precision measurement (constant monitoring of group temp and extraction pressure, weighing shot output etc). And I recognize that for some, that's exactly the fun part, and my approach (weigh beans, grind, do my best with meticulous basket prep, pull shot) is unappealing.

But that's all fine, we each get from this hobby what we want and what works for us.

The suction from pulling multiple times doesn't happen on all designs...some have a valve that prevents the water from flowing anywhere when lifting the lever. I would love to talk in person and show you guys what I mean...message me if you're ever near Lancaster Ohio and bring your favorite beans