Preinfusion on the La Marzocco GS3

[laservet]

For those who have one, how is preinfusion accomplished? Is it needed?

[HB]

The GS3 has a solenoid that interrupts the pump for a programmable amount of time. That is, pump goes on... pause 1... solenoid closes... pause 2... solenoid reopens. You can set the length of pause 1 and pause 2. From One week with the La Marzocco GS3:

As Ken and Jim documented in How to Preinfuse; Extraction Pressure Redux, there is arguably a benefit to preinfusion under mains pressure ("At 3 bar, good stuff is happening, the water has enough pressure to go through the whole puck in a reasonable time."). That's not an option for espresso machines drawing water from a reservoir, but the GS3 does provide start-stop-start preinfusion by closing / reopening the grouphead solenoid in the early seconds of the extraction.

Lino stopped by this evening to help plot the GS3's pressure profile resulting from this design:


The "speed bump" is the on/off pulse

The thread Pressure profiles, preinfusion and the forgiveness factor shows the pressure profiles of several other espresso machines. This profile resembles the Elektra A3's no preinfusion design, except for the small speed bump and a less inclined rise, presumably thanks to the GS3's smaller diameter gicleur. Lino and I were surprised to see that the group depressurizes and repressurizes after the preinfusion cycle. I programmed in one second of pressurization followed by two seconds of dwell time. While I haven't tried it yet, I assume that allowing much longer would mean a higher rise and fall, which could disrupt the puck's adhesion. Given the GS3's already easy nature, I wonder if it would improve further still with a higher pressurization to 3 bar and no depressurization as How to Preinfuse advocates?

You can hear the solenoid close and reopen in this video:

[roblumba]

I've been using pre infusion regularly now. Mainly for the forgiveness factor, but I wonder if it really is being any more forgiving. I have a LM naked portafilter that should arrive today or tomorrow. I do plan to see how it effects extraction over time. Perhaps there's less chance of channeling or whatever with the short preinfusion.

Basically, although the preinfusion doesn't show much of a difference in the pressure profile, except that little bump. Nevertheless, there is a small amount of water which ejects onto the puck and presoaks the top of the puck . This may or may not help when the puck is coming up to full pressure.

I was told by Tim at Pacific Espresso that La Marzocco has done research on the pre-infusion and they couldn't find any taste difference.

You might also notice that the default is "off" for pre-infusion.

Despite these facts, I still turned it on because psychologically I somehow think it will still help cover me in the case that I make a mistake in distribution, tamp, whatever.

On the other hand, it does mess with the chronos when you consider that the real brew time does not start at 0 seconds. So when you have the chronos function on and pre-infusion, and you are looking at the timer, you have to figure in that there's approximately 3 seconds of pre-infusion time (I have mine set at .9 seconds on / 2.4 seconds off for a double).

[luca]

I think that it would be helpful to clarify some terminology here. Frankly, I have no idea what preinfusion technically means, or, indeed, if there is a settled definition. It would be nice if someone could comment on that. I use it to refer to anything that basically slows the initial flow rate down and I think that I'm not alone in that. Preinfusion in this sense can be accomplished via a gicleur, which basically does nothing more than just a narrowing of the tube carrying the brew water. (Correct me if I'm wrong!) Gicleurs can be installed in La Marzocco machines and I'm pretty sure that they come standard on all machines now (at least in Australia). Common sizes are 0.6mm and 0.8mm; there might be a 1mm gicleur as well. The smaller the diameter, the longer time it takes to see the first drops of espresso. If you are thinking about e61s when you are thinking about preinfusion, it might interest you to know that e61s also have a gicleur in the group to do precisely the same thing. Then there's the pump on/off thing that everyone has already discussed.

I'll leave the merits of "preinfusion" - however it is defined - to another post.

Cheers,

Luca

[Jepy]

I think that it would be helpful to clarify some terminology here

I'm not sure the proper term, but because my machines have adjustable settings I call the first part "soak"(lower pressure regulated), then the second part where the traditional gicleur is used, I call it ramp. I guess both parts to some would be preinfusion.

[roblumba]

Perhaps it's better to group everything that happens with brew water, prior to the main infusion as pre-infusion.

The ramp-up seems like a way to provide a short amount of preinfusion immediately coupled with the full pressure infusion.

The La Marzocco's pre-infusion setting provides for even more control over this pre-infusion by allowing for custom setting of pre-infusion that can be changed according to the user's desire. On the other hand, the pre-infusion of a gliceur is short, pretermined albeit has it's own desirable quality of it's own. Also, consider the properties of the gliceur are duplicated during the custom pre-infusion phase because the gliceur is a physical part of the machine that cannot be turned on or off.

Now those are difference between methods, but what are the differences with the results! I'm not quite sure about that. According to La Marzocco research, there is no benefit. I've yet to discover for myself. I've had it on for a while and things are going good. Next, I need to turn it off and see if things get worse or better.

Perhaps what happens is I end up adjusting my extraction technique, temperature, grind, etc, to match the results I'm getting. So either way, I end up getting to the same results.

[malachi]

It's "pump-pulse" pre-infusion.
The pump goes on for a programmable amount of time, then shuts off for a programmable amount of time, then goes on again.
The idea is to "pre-saturate" the coffee before beginning extraction.
This is not the "gentle pre-infusion" that you would get from some other techniques (line-pressure pre-infusion or gravity pre-infusion for example).

The topic of "is pre-infusion valuable and effective" is a complicated one.
Before beginning it, however, it is important to differentiate the topic as there are four embedded topics here.
1 - Is pre-infusion at a concept level valuable and positive.
2 - Is pump-pulse pre-infusion valuable and positive at an experiential level.
3 - Is line pressure pre-infusion valuable and positive at an experiential level.
4 - Is pump-pulse or line pressure "better".


Restriction via jet/gicleur is not "pre-infusion" but rather a change to the profile (water debt, pressure ramp).

[houdina]

Some machines like the LM GS2 with its paddle group let you pre-infuse the puck with water at a lower pressure than the 9bar the pump makes. It allowed water at supply line pressure to saturate the puck before the pump was turned on.

I am not sure if the GS3 is hooked up to the water suppy, if it will work the same way without the pump running during pre-infusion.

[malachi]

Some machines like the LM GS2 with its paddle group let you pre-infuse the puck with water at a lower pressure than the 9bar the pump makes. It allowed water at supply line pressure to saturate the puck before the pump was turned on.

Line-pressure pre-infusion.

[Nick]

Pre-infusion on a machine with heavy flow restriction (like the 0.6mm restrictors on the GS/3) is redundant.

Stick with the pre-infusion set off.

[Matthew Brinski]

Pre-infusion on a machine with heavy flow restriction (like the 0.6mm restrictors on the GS/3) is redundant.

Stick with the pre-infusion set off.

Is that for sure? I understand that it may be redundant concerning possible increased forgiveness, but what about extraction/flavor profiles? I'm not necessarily disagreeing with you. If that's the case though, the paddles on the recently tested LM in Vancouver (and the eventual paddle kit for the GS3) is just a bunch of show-boating, no?



Matt

[luca]

Is that for sure? I understand that it may be redundant concerning possible increased forgiveness, but what about extraction/flavor profiles? I'm not necessarily disagreeing with you. If that's the case though, the paddles on the recently tested LM in Vancouver (and the eventual paddle kit for the GS3) is just a bunch of show-boating, no?

I worked at a cafe with a Cyncra and we found that the line pressure position on the paddle was cool, but didn't really result in a better tasting cup or a more forgiving extraction, so we just moved the paddle all the way to the left. Nick has a Synesso around somewhere, so it would be interesting to hear what he thinks. I haven't heard of anyone seriously using the line pressure position on the Cyncra lever in a cafe.

Sitting half way across the world from the action, I have heard conflicting reports about the various LM paddle groups that have been around. Some have said that they are effectively a three position switch, like the Cyncra paddle. Others have said that they are an improvement over the Cyncra paddle in that you can do all out pressure profiling with them. (Not sure how the earlier LM paddle groups worked.) If the latter is the case, then the new LM paddles might allow for even niftier things than preinfusion, like gradually reducing the pressure before stopping the shot - there's a video on the LM site with Bill Crossland saying that you can vary the brew pressure. I think that Greg did some experimentation on that with his own rig not too long ago. If the LM paddles are just a glorified three position switch, then I'd say that they're probably still more than showboating just because paddle groups are nice and ergonomic to use.

Cheers,

Luca

[Jacob]

It's "pump-pulse" pre-infusion.
The pump goes on for a programmable amount of time, then shuts off for a programmable amount of time, then goes on again.

The motor keeps running, it's a solenoid that's closes and opens!

I am not sure if the GS3 is hooked up to the water supply, if it will work the same way without the pump running during pre-infusion.

Nope, but with a software-update it should be possible!


Usually the paddle-group controls pre-infusion, but people have been talking about a version that controlled the brew-pressure instead - I would love to know more about this

coffeed.com:

I assume a few folks got to play with the concept Linea with paddle groups at the SCAA show. You could control preinfusion and the brew pressure with the paddles and watch the pressure changes in real time on the gauge. It was tha sh**! I pulled some shots using ideas from this thread and got some interesting results. Also pulled some shots trying to mimic the profile from a lever machine and got similar results. Unfortunately I only got about 6 shots pulled until I was feeling the pressure to move on. The ESI folks said that when this design comes out (a few years maybe) you will be able to retro-fit Lineas and GB/5s to use the paddles. FYI you can only control the pressure of one group at a time. Any other feedback on this machine...MarkP, AndyS, GregS...did ya'll check this thing out?

Now that's cool! I saw it, and like an idiot I didn't ask Bill what the deal was with it. Duhhhh. Damn!

-Greg

Yeah Greg,
I've kinda been surprised that folks haven't been talking about it more. The dude I talked to at the booth said I was the first person to say, "Holy sh**! I can pull shots to mimic a lever machine with this thing!" (could that possibly be true as of Sunday afternoon?) Honestly, I find it hard to believe that no one else saw/played with this thing... anyone?...anyone? I mean, we'll (in the future) be able to retro-fit GB/5s with the paddles! Am I the only one freaking out here!?! Is this not as great as it seems? Am I missing something?

[Matthew Brinski]

I worked at a cafe with a Cyncra and we found that the line pressure position on the paddle was cool, but didn't really result in a better tasting cup or a more forgiving extraction, so we just moved the paddle all the way to the left. Nick has a Synesso around somewhere, so it would be interesting to hear what he thinks. I haven't heard of anyone seriously using the line pressure position on the Cyncra lever in a cafe.

I gathered the same thing last year when I asked a couple of baristas at Espresso Vivace about whether they manually preinfuse with the Cyncra paddles. Similiar to Nick's statement (and yours), they replied that it wasn't beneficial due to the restricted pressure ramp up that the machine exhibited. I was curious about the size of the gicleurs, but they didn't know.

I'm just curious about whole preinfusion thing still, especially regarding the different methods that are claimed to be preinfusion:

Pump-pulse
Restriction jets
manual line pressure
lever
E61 group head designed

etc.

It may seem like "old news" to most, but I haven't been able to really find any relatively conclusive information about the benefits of one type over the other - that is, if any benefits exist at all.


Matt

[malachi]

Also... with a Synesso, if you're pulling a shot on one group I don't think there is any way to preinfuse on a second group (correct me if this has changed). So commercial use of preinfusion is unrealistic.

[pdx]

Also... with a Synesso, if you're pulling a shot on one group I don't think there is any way to preinfuse on a second group (correct me if this has changed). So commercial use of preinfusion is unrealistic.

That's correct- the water comes through the pump at line pressure for preinfusion, so if the pump is on you get 9 bar rather than line pressure. I guess you could bump the preinfusion switch quickly on the second group- you would end up with the same "pulse" preinfusion scheme that the GS3 uses.

I wouldn't bother, though. I only use the preinfusion position on my Synesso to bleed some water after shots to clean the screen, not for shot pulling.

[Nick]

Well, paddles are, frankly, more fun to use than a switch.

I got to play with the La Marzocco FB/80 paddle machine in Vancouver. The paddles work differently than the Synesso groups... but with one key similarity.

Differently, because the Synesso paddles are two-stage switches. There are two micro-switches that are actuated at the middle and full-on positions on the paddles. The first "pre-infusion" switch opens the solenoid, the second switch actuates the pump. So it provides the somewhat-coveted "line-level pre-infusion."

However, the Synesso paddles are akin to autostick/tiptronic transmissions in cars. They resemble "true" paddle groups, just as auto-stick transmissions resemble traditional manual transmissions in the way you shift... but just as "real stickshift" includes a manual clutch-flywheel mechanism and is fundamentally different from a manual tranny, a "real paddle" is different.

The Marzocco paddle on the WBC-candidate machine was a "real paddle." As you move the paddle, the water begins to flow in an analog, progressive way that increases in flow as you move the paddle to the left. Fully-on, the pump kicks in. I don't know enough about the older paddle-group machines to be able to compare this LM group to them, but it's pretty cool nonetheless.

The key similarity is that when the pump is on, the pump is on. In other words, when one group is fully-on, the other groups act differently, because the pump is on for all groups. The rate of flow is still progressive depending on paddle-position, but it acts as you'd expect, with more flow on the group at the same corresponding paddle-position, compared to flow when the pump is off.

All said, I still don't see the point. I confess that I didn't get to make any coffee with the paddle LM, so maybe there are some improvements to the coffee quality with a particular paddle-technique. I think Mr. Champion/Hoffmann did... any feedback from you?

[micki]

What worries me about the GS/3 infusion is that the pressure is released at end of the "preinfusion" ... I don't like the idea that some good stuff is going down the drain, that should have been in my cup. I have ceased using preinfusion and am not going back (maybe if I get a paddle group ... )

Kim

[AndyS]

What worries me about the GS/3 infusion is that the pressure is released at end of the "preinfusion" ... I don't like the idea that some good stuff is going down the drain

If the parameters are set properly, I don't believe a significant amount of pressure is built up. And I also don't believe the three way is opened during the dwell time...but it's been a while since I played with a GS3.

[roblumba]

The default pre-infusion setting on the GS3 only let's out enough water to soak the puck. There is not sufficient pressure built up for anything to go down the drain at de-pressurization.

Nevertheless, I've turned it off recently. Unfortunately, I also changed blends at the same time so I don't really know how it effected the shot quality but using a Naked portafilter, it seems to be extracting just fine. I think I'll probably need more time to really become intimately familiar with how pre-infusion effects the shot because I don't go through pounds of coffee, doing taste test. I just do my normal routine and consume the coffee at my normal rate.