Levers and lower crema production

[Abdon]

What's the story behind the statement that when it comes to crema production, levers are not as good as pump machines?

My Gaggia Achille seems quite capable of producing 100% crema shots with striping on the top. Not consistently, but that seems to be more my own fault

What am I missing?

[chopinhauer]

What are you missing. Well, the crema should overflow the glass or cup and never EVER dissipate.

No seriously, you don't seem to be missing much and are getting the sort of crema that good pump machines produce. My pavoni and cremina produce decent crema, but not as much as that produced by my Silvia, when I owned it. On the other hand, regardless of crema, my levers produce much better espresso (to my tastes) than the Silvia.

[mogogear]

You are missing the royalties that we all would pay you for publishing your top secret routine!

I think we all intentionally try to keep peoples expectations down about CREMA, so it comes off like we all drink flat espresso! Folks that come over from HX rotary machines have crema factories that they can be used to... or those new to levers get all this esoteric stuff and a new learning curve at the same time- so we seem to beat ourselves a little about thin crema.... possibly inadequate crema- When we know it is really about how the espresso tastes. Crema insecurity !

What say you folks?

So share... we could name a routine after you ....

[peacecup]

IMHO, crema is overrated. And I'm a crema-nut. The point is that just because there's crema don't make it espresso. I.E. great espresso has to have great crema, but great crema does not mean great espresso. Now, I've made some bad espresso on my lever machine, but not too often, especially after the introductory period. Conversly, its easy to make bad espresso with a pump machine.

I'm beginning to think that putting 15-bar pumps on espresso machines was a mechanical expedient, not something that was developed and tested to make better espresso. Someone may call BS on me for this, but it may just be that lever machines get the most there is to get out of roasted, ground coffee beans. Look at it this way, all the technological improvements made in the music world since 1969 have not produced anything like the Beatles or Jimi.

PC

[Abdon]

So share... we could name a routine after you ....

I just followed the instructions/suggestions/guidelines found on this very forum and it worked from day one. I'm just the monkey jumping on the lever; all credit belongs to you guys A home roasted blend which has about 50% Ethiopian harrar (half of that city+, half full city++/Vienna) 50% Tarrazu (city+) doesn't seem to be hurting things.

I'm still saving my pennies for a Mazzer. in the mean time a $30 Hario hand grinder with ceramic burrs is doing a commendable job. Not the most efficient nor convenient, but the results are superb.

One things that makes me wonder is the presence of holes on the spent puck. They seem to come from air escaping the puck during the preinfusion. Should I worry about it?

[HB]

What's the story behind the statement that when it comes to crema production, levers are not as good as pump machines?

That comment is typically applied to spring-powered levers, not manual levers like your Achille. While I've not measured the brew pressure of my Elektra Microcasa a Leva, Lino calculated its spring is capable of generating about 6 bar at its peak, tailing off to 4 bar. Perhaps needless to say, the crema production of an electric pump machine set to 6 bar is a lot less than one set to 9 bar; the same observation applies to spring-powered versus manual levers. Whether the loss of crema production is offset by a more appealing taste profile is frequently debated.

[Bushrod]

IMHO, crema is overrated. And I'm a crema-nut. The point is that just because there's crema don't make it espresso. I.E. great espresso has to have great crema, but great crema does not mean great espresso. PC

I disagree. My La Peppina and Elektra Leva both make great espresso. They don't, however, make great crema. I'm slowly getting used to that fact.

[timo888]

The quality of the crema is more important than its quantity.

[peacecup]

IMHO, crema is overrated. And I'm a crema-nut. The point is that just because there's crema don't make it espresso. I.E. great espresso has to have great crema, but great crema does not mean great espresso.

I disagree. My La Peppina and Elektra Leva both make great espresso. They don't, however, make great crema. I'm slowly getting used to that fact.

The quality of the crema is more important than its quantity.

Right, that's what I meant - great crema, not more crema!

[Bushrod]

Ah, now I get what you're saying.

[A2chromepeacock]

What are you missing. Well, the crema should overflow the glass or cup and never EVER dissipate.

like this? (okay, so not a lever machine, but a fun video nevertheless...)

[Abdon]

That comment is typically applied to spring-powered levers, not manual levers.

That makes sense. On my machine crema gets the thickest on hard pulls. Higher pressure seems to give better crema but then it also looks like _for the same volume_, higher pressure = faster extraction. With lower pressure, I can get a good 1.75 oz. shot. At higher pressure, the stream begins to turn lighter at an earlier stage. I can (quite literally) see how pressure changes the extraction look, feel, and taste. This statement needs more testing which I'll be happy to conduct

One thing I read everywhere was that learning a manual lever was hard. This notion is a disservice to people thinking about buying a manual lever. There is NOTHING complicated about learning to consistently apply pressure. I learned by running water through the machine, and timing 25-27 second lever travel times. This is made easier by the fact that at 13~14 seconds, the lever should be at a 90-degree angle. Once you do that about a hundred times, you just learned how to use a manual lever and didn't even have to ruin a single shot

I honestly believe that it is that simple. Once my body learned to time 25~27-second shots no matter what, it was all on the grinding and tamping. Anything at all that could go wrong, had nothing to do with altering the 25~27-second travel of the lever, therefore there is no point on worrying about it. If your grind/tamp is right, the mouse tail will tell. If it is wrong, changing travel speed will only develop inconsistency and a bad habit.

[chopinhauer]

Yes, A2chromepeacock, that video captures exactly what I was talking about, except of course my crema never dissipates...NOT! Wow, what a coffee, in appearance at least.

[ogatasan]

That makes sense. On my machine crema gets the thickest on hard pulls.

For me a harder pull (actually push) way over the 9 bar results in a thinner and dissolving crema and a somehow complicated and slightly agressive taste with a tendency towards overextraction.

Can someone enlighten me on the pressure curve of the Pavoni? i assume that if 9 bar are needed i get a support of around 1 bar from the preexisting pressure, but only as long as water can enter the grouphead. After that point I imagine that i have to provide the full 9 bar pressure.

On the bigger picture I have no idea how this thought might apply to pump machines.

Once again I hope I make any sense...

[timo888]

Can someone enlighten me on the pressure curve of the Pavoni?

The manual lever espresso machine itself does not have a pressure curve. The pulls have the pressure curve, not the machine, because the force on the lever is variable (as is the puck/cake). However, there are some constants:

The brew pressure is a function of how hard you press down on the lever, the lever's physical characteristics, the size of the piston cylinder (and on the flow rate through the cake, but that's an attribute not of the machine itself but of the medium-i.e. dose, compaction, height-to-width ratio, etc).

The lever multiplies the force of your muscle according to the lever's length and the distance between the fulcrum and the piston rod. The smaller the distance between the fulcrum and the rod, and/or the longer the lever, the greater the mechanical advantage, i.e. the more force brought to bear using the same muscle power. The greater the cross-sectional area of the piston cylinder, the greater the force required to achieve a target pressure. The narrower the piston cylinder, the less force required.

So, when comparing the physical dimensions of manual levers, you can look at the lever arm, the distance between pins and rod, the diameter of the piston cylinder. If you have a long lever, with close-set pins, and a relatively narrow piston cylinder, you have a lever designed to make it easier for the arm to reach a target brew pressure than a machine with a smaller lever, more distance between pin and rod, and a larger piston cylinder.

Regards
Timo

[ogatasan]

Timo,
Excuses for my bad english.. next time i better do it in german and feed babel fish

What I meant and wanted to know is how the preexisting boiler pressure influences the pull... obviously at least during preinfusion there is a pressure of 1 bar hence leaving 8 bar (the rough equivalent of 16 kgs pressed on the center of the handle on the Europiccola).

for a laugh:
http://www.home-barista.com/forum...2356-80.html#51841

so if there was a curve reading the boilerpressure on the puck would there be a sudden jump from around 1 bar to 0 as soon as the Piston cuts the water- inlet?

[timo888]

I realize your question has physics at its core, but let me answer in a practical manner.

Boiler pressure has important ramifications for the preinfusion : with the boiler pressure high enough, you can get a drop in the cup by boiler pressure alone; with lower boiler pressure, it also takes some lever effort to preinfuse the coffee and get a drop in the cup. But boiler pressure contributes little if anything to the infusion proper. During the infusion phase, you are creating perhaps 7-11 atmospheres of brew pressure with the lever. Also, as the piston comes down, the port to the boiler is sealed shut, so the boiler and cylinder no longer form a continuum.

Regards
Timo

[peacecup]

Greater boiler pressure will allow the piston chamber to fill faster, but as timo says, this is sealed from the boiler once the lever is pulled. All pressure during extraction is created by the piston.

I am by no means sure that greater pressure = better crema. I must concede that it makes more crema.

I am beginning to think that at greater pressure individual air bubbles in the crema are larger. This may result in more crema, and more body, but overall flavor in the cup may not necessarily be enhanced (of course taste is an entirely subjective personal preference).

PC

[pab]

The piston lever has always the boiler pressure on its top, when you raise the lever and also during the pull. Hence pressure on the coffee is produced by force on the lever + boiler pressure (example: 8bar from manual force + 1bar from the boiler= 9 bar on coffee puck)

I've read on this forum how a Gaggia Achille works. The lever push water into the group just like an electric pump. The group is exactly like a pump Gaggia machine. It's very different from a standard lever machine where all the water fill up a chamber directly on top of the coffee puck and then it's pressed through it.

[HB]

The piston lever has always the boiler pressure on its top, when you raise the lever and also during the pull. Hence pressure on the coffee is produced by force on the lever + boiler pressure (example: 8bar from manual force + 1bar from the boiler= 9 bar on coffee puck)

Not true for the lever machines I know. For example the Olympia Cremina:


Hydraulics diagram of Olympia Cremina

The incoming port is cut off by the piston through most of its stroke. In the case of the Microcasa, the area above the piston is open to the outside. You can see the upper hole in this photo:



I believe the La Pavoni Europiccola is the same way, i.e., there is a hole on the backside of the grouphead above the bridge to allow air to escape during the upstroke. The Cremina avoids this by adding the second channel shown above. It has the added benefit of allowing the barista to quickly heat the group with short up/down strokes, which pulls water in/out of the boiler (a trick pointed out to me by LMWDP founder Steve Robinson).

Dave explains the Achille's pump system in the Buyer's Guide to the Gaggia Achille. It's unique, that's for sure.