A Soft Pull Technique

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KarlSchneider

#1: Post by KarlSchneider »

A couple of recent threads lead me to ask if others have tried the following in a manual lever. Like everyone I sporadically grind too fine and/or tamp too hard for my Olympia Cremina. I immediately notice the symptoms of what is usually called choke. I note in my instinctive reaction to this sensation the tendency to apply more force. For reasons unknown on one of these occasions I did something counter-intuitive. When I felt the tell-tale resistance I reduced the force I was applying instead on increasing it. I continued the application of force and did so on a uniform level but at a reduced amount. The result was a successful pull although not a great one. I find this backing-off instead of ratcheting-up to work very well in these circumstances.

Have others noticed this?

KS
LMWDP # 008

caeffe

#2: Post by caeffe »

KarlSchneider-

I too have noticed this while using my Europiccola.
I found that by hesitating on the pull, the pressure let's up and it 'unchokes'. Maybe some of the pressure is relieved, where to? I'm not sure. For me it wasn't intuition - it was that my arm felt tired so I let up on it and upon continuing it somehow got easier.

Since this doesn't happen often and I don't have my tamping force measured, I'm not sure I can say that I'm able to 'unchoke' all the time. I'll pay a little more attention next time this happens.

I probably get this to happen on occasion possibly due to overtamping as I don't have a means to measure my tamp as my bathroom scale is digital and doesn't indicate a weight until it is stable.

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hbuchtel

#3: Post by hbuchtel »

Yes! :D Don't you love that feeling of slow release under the weight of your hand?

I've sometimes gotten a little gush of espresso after easing off on the pressure... makes no sense at all :roll:

Henry
LMWDP #53

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starry

#4: Post by starry »

I have also experienced it. Also, after a few drops emerge, the pull gets easier. I think that's because some of the solids from the puck are disolved and are moved into the cup therefore making it easier for water to flow.
Ralph Walter

Javier

#5: Post by Javier »

hbuchtel wrote:Yes! :D Don't you love that feeling of slow release under the weight of your hand?
I have had that experience with my Gaggia Factory. I believe Alchemist mentioned something similar in that huge thread about adding a pressure gauge to the Pavoni lever machine.

Javier
LMWDP #115

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Alchemist

#6: Post by Alchemist »

Ok, Javier beat me to the punch. It's pretty classic bed compaction. Pressing to hard for a given bed (grind) just compacts the bed and stops the flow. Buy backing off the pressure, you open up space between the particles and allow flow through. What you can also do is increase the pressure once you have flow as long as you do it delicately and don't hit the bed's maximum threshold.

I use this technique all the time on my HPLC columns at work. Start ramping pressure via flow, note the pressure 1/2 way up is higher than it should be, reduce flow to reduce pressure, watch the pressure non-proportionally drop (as the bed relaxes), then ramp the flow back to where it should be and see the pressure follow suit and not over pressurize. If I were instead to allow the flow to spike the column pressure I would compact the bed and kill a $900 column :shock:

Mind you, on an hplc the time is minutes, not seconds like on a pull, but I have found the theory holds true. Oh, but this is not to say the shot is great - it just doesn't choke.
John Nanci
Alchemist at large
**
LMWDP #013

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KarlSchneider

#7: Post by KarlSchneider »

Alchemist wrote:Ok, Javier beat me to the punch. It's pretty classic bed compaction. Pressing to hard for a given bed (grind) just compacts the bed and stops the flow. Buy backing off the pressure, you open up space between the particles and allow flow through. What you can also do is increase the pressure once you have flow as long as you do it delicately and don't hit the bed's maximum threshold.

<snip>

Oh, but this is not to say the shot is great - it just doesn't choke.
This was my guess. I had this post in mind

The role of fines and what we really want from a grinder

And I fully agree that such shots are not close to great. They don't choke and are drinkable usually.

KS
LMWDP # 008

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TUS172

#8: Post by TUS172 »

When I first began with my Pavonis I had quite a few chokes. One thing I tried and it work wa to pull up quickly on the lever to release the puck and cause a bit of a temporary vacuum (if you can call it that) and then gently reapply pressure. That also worked but it can cause a fissure in the puck... you already know the result... :? A good chance of having a "Sink Shot"
Bob C.
(No longer a lever purist!)
LMWDP #012

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espressoperson

#9: Post by espressoperson »

My best shots on the Olympia Cremina are usually just a couple of shades above a choke. I always try for a strenuous leaning on the lever to produce about 1.5 oz in about 25 seconds through about 15 g lightly tamped grinds. If a pull gets too close to the choke side I continue a steady pull but with much less pressure than usual. Almost always that will push through the puck and once started, the pressure can be increased, but not quite getting to a full pressure pull. Still, these shots can be good if all other elements are sound - no signs of channeling, no over or under extraction, etc.

Unlike some of the descriptions above, I find that letting up on the lever when experiencing the choke makes it harder to push through. The steady but light pressure with no let up to get the flow started works better for me.
michaelb, lmwdp 24