I pull lightly on my euro until it shows drops, then pull down harder to achieve normal flow rate. My idea is that it emulates progressive pre infusion found in high end machines. I find this to be way more effective than boiler pressure preinfusion, and I've never seen any evidence of channeling in any of my pucks, and my flow looks very similar to pro machines. Tastes great too. Im dosing around 15-16 grams.

Using an effort scale of 1 (no effort) to 10 (hanging on for dear life), my typical pull on the Cremina is to start around 6-7 and continue at this pressure while the first drops appear and the cone forms. Once the cone is formed, I'll start lightening up on pressure, keeping just enough to maintain a constant flow. Over the course of the shot, the perceived effort moves from a 6 down to a 4, by which time I've usually hit my desired shot ratio weight.

I haven't done direct measurements of pull pressure, but you've given me an idea. I've got an old spring scale around here, and will put the Cremina on the scale while I pull some shots. That should provide something more real than the 1-10 scale.

Sherman wrote:Using an effort scale of 1 (no effort) to 10 (hanging on for dear life), my typical pull on the Cremina is to start around 6-7 and continue at this pressure while the first drops appear and the cone forms. Once the cone is formed, I'll start lightening up on pressure, keeping just enough to maintain a constant flow. Over the course of the shot, the perceived effort moves from a 6 down to a 4, by which time I've usually hit my desired shot ratio weight.

I haven't done direct measurements of pull pressure, but you've given me an idea. I've got an old spring scale around here, and will put the Cremina on the scale while I pull some shots. That should provide something more real than the 1-10 scale.

I might try setting my Cremina on a scale and see if I can get some readings too.

Thats interesting that you ease up on the pressure. My mentality is that if I start slow and let the puck saturate more gently, then it will be less likely to channel, and then I can pull down harder throughout the rest of the shot. Why do you start hard and ease up?

Evan, I do the same on my Cremina - start hard and ease up near the end of the pull. Reason for the harder effort in the beginning is that there is more resistance. Near the end, the resistance is far less, and either continuing with the same force, or increasing would push water through the puck far more quickly.

I have no sound logic for easing up when resistance eases - it just seems like the right thing to do in order to maintain constant water flow through the puck. In the name of "science", I should try a continuous-force pull, but I'm not sure I want to change what is yielding amazing results.

On a related note, my spring-assisted PV Lusso, pressure also eases up near the end of the lever's action... but that has to do with the properties of a spring - when fully compressed, the opposing force created by the compressed spring is greater than when the spring is nearer a neutral (relaxed) state. Have to dig up my college physics books to get the realistic formula showing that a spring is not linear. So, really, I'm subconsciously trying to replicate a spring lever!

A question for those that start with firmer pressure and then ease up, are you using a separate pre-infusion step?

I agree that declining pressure would tend to mimic the action of a spring lever, but with my La Peppina, I like the 14 g double shots where I've done a 10 second pre-infusion before letting the spring do the work. For 7 g singles, though, I find that any pre-infusion tends to over-extract the shot so I just pull and go with a single.

Yes, I do a partial pull to preinfuse. I try to stop this partial pull before I get any coffee out of the PF, but I'm not always successful there!

Bob,

I'm with you there, I try to stop before any coffee exits the PF, but I'm not always successful either. This is especially difficult with a spouted PF (the La Peppina PF handle is attached to the spouts making going bottomless a bit more extreme).