La Marzocco GS/3 MP Review

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#1: Post by HB »

Although the Marzocco GS/3 MP is a fully commercial espresso machine with enough capacity to cater a small wedding, it's nicely sized for the home:

La Marzocco GS/3 MP evaluation model courtesy of Chris' Coffee Service

The model above sports a paddle that enables the barista to easily control the length of the preinfusion. Because the pump is controlled manually, the barista must also monitor the extraction and decide when to stop it. In contrast, the AV model's preinfusion time is programmed and the AV's bank of four push buttons can be programmed for various shot volumes (single, double, lungo, etc.).

UPDATE: Read the final writeup La Marzocco GS/3 MP Review.
Dan Kehn

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#2: Post by HB »

I apologize for the lack of updates for this review. Other obligations and events like the SCAA 2013 Reports demanded my attention. Before continuing with my own observations, I would like to excerpt key points in Chris Tacy's 2005 review of the La Marzocco GS/3 prototype:
Chris Tacy wrote:First Impressions

La Marzocco is well known within the professional coffee community. Founded in 1927 in Florence, Italy, La Marzocco rapidly became recognized as an innovator within the espresso machine world. With the original GS machine in 1970, La Marzocco established themselves as the creators of the dual boiler, semi-auto espresso machine. With the GS, the company earned a reputation for producing cutting edge (and high priced) commercial espresso machines. The original GS machines have become desirable collectors items. La Marzocco followed the GS line with the espresso machine that would become the gold standard for commercial use— the Linea. While various collectors have used GS machines at home and some fanatics have installed Lineas for their home use, La Marzocco had never seriously considered creating an espresso machine suitable for the US home market until the last few years. The GS3 is a logical extension of the storied GS line and the first La Marzocco machine that has been designed to be easily used in a US home installation.

At the same time, while one could categorize the GS3 as a "home machine," it would be more accurate, in my mind, to call it a light-duty commercial or a catering espresso machine. It just so happens that many of the requirements of such a machine overlap with the requirements of a home machine (110V power, portable, compact size, easy to use, no plumbing requirement). There are, however, small giveaways to the true nature of this machine; for example, in one programming mode you have the option to set a day of the week that your shop is not open for business so that the machine doesn't turn on. A significant giveaway is that the rumored price range, which may be considered reasonable for a commercial machine, is well outside the current home market price range.

Despite the warnings, I was still shocked by how small the GS3 is (21"w, 16"d, 13.25"h for the prototype). It is very hard to believe that this little box contains two boilers, a reservoir, pump and motor, electronics, plumbing. It's like some sort of clown car trick. This may seem like a minor point, but in many ways it is one of the most profound "wins" of this machine. Due to its compact nature, the GS3 can be easily fit into just about any small commercial location or home location and, perhaps more interestingly, is actually reasonably portable. This is valuable for the potential catering market and, as you'll see later in the review, it also can be quite worthwhile for the home user. In addition, this finally puts to bed the long-held belief that, in espresso machines "bigger and more massive" (as Andy Schecter would say) is always better.


From talking with Bill Crossland, it was clear that one of the primary goals in developing the GS3 was to make a simple to use machine. In this he was entirely successful. Using the GS3 is practically foolproof compared to any heat exchanger espresso machine I've used—and is noticeably more straightforward than even a Linea.

With heat exchanger (HX) espresso machines, you need to become a master of brew temperature management. Through various flushing methodologies, you manually deliver the target brew temperature. This is the largest single challenge of these machines. With some HX machines, the requirements of flushing are simplified, particularly with the high-end commercial HX machines. But even with these machines, managing brew temperature requires skill, particularly when starting after a long idle period.

Even with the existing dual boiler machines, it is important to understand the relationships between idle times of various durations and brew temperatures. Machines like the Expobar Brewtus have issues with this due to the group design. Automatic Lineas have different issues due to the placement of the flowmeter in the brew pathway. Indeed, semi-auto Lineas provide the best results when flush-managed.

This is not an issue with the GS3. If you so choose, you can get good to great results while ignoring flush methodologies entirely. In my case, and probably motivated by tradition and paranoia, I merely programmed the "short single shot" button to provide a one ounce flush and hit that immediately before pulling any shots. This worked perfectly for me. With it, flushing became dead easy.

The combination of the dual boiler set up and the simplified (or lack of) flushing results in a machine that is easier to use than anything I've ever worked on. To make life even better, the GS3 also provides a number of additional treats to simplify the barista's work.

Espresso Performance

Over the course of the evaluation of the GS3, it became a object of great desire and even lust for all who pulled shots on it. In every case, the discussion rapidly proceeded from "is it a good machine?" to "do I like it?" to "is it better than X?" (fill in "Linea" or "Synesso" for X) and eventually to "is it the best machine you've used?" Drips of a naked pourand finally to "oh I want one!" This conversation was largely fueled by the results when pulling shots.

As with any espresso machine, to quote Dan Kehn, "The problem is on the handle side of the portafilter." This has never been more true than with the GS3. Finally, the espresso machine "gets out of the way" of the barista. If there are problems with your espresso, just accept that it's your own fault. Either you are using the wrong coffee, the wrong grinder, have maintained things poorly, or (most commonly) your barista skills need work.

Steaming Performance

The GS3 on full power has impressive steaming performance. While it is not on par with a commercial 220V Linea, it's damn close. In fact, I am afraid that most home users are going to have a hard time getting used to working with this sort of power. A six ounce pitcher of milk takes about 3 seconds to stretch and another 3 seconds to steam. You have to work quickly and very, very smoothly if you want good texture. On the other hand, once you know how to use the power there is no going back. The ability to stretch without over-heating the milk allows for the creation of incredibly sweet textured milk.


In most ways, this is a "no compromises" espresso machine. And as a result of this, it is a breakthrough machine.

It is important because it shows us the way forward. Sure, it's a fantastic espresso machine in and of itself. But the true value in this machine is what it will create. As a result of the GS3, we should see the adoption of key technologies from it throughout the espresso machine market. With any luck, this machine will become the emulated benchmark that the original E61 once was. In addition, and perhaps of even greater (though more subtle) value, is what this is going to create within the coffee community. It is entirely possible that this machine will enable the current generation of baristas and roasters to see personal breakthroughs in the understanding of espresso. And this should lead to dramatically improved espresso for all of us.

And that is why this is an important machine.

In addition, I've mentioned the incredible espresso performance already, but something else needs to be pointed out. In the past, it has been deeply frustrating to learn about espresso through experimentation. Even the supposed constants in the process (brew temperature, brew pressure, etc) have actually been variables. This has resulted in a massively complex, multi-variable problem that made drawing conclusions more akin to a Seance than Science. This has also made evaluating and tuning espresso blends and bean roasts very frustrating and time-consuming. With the GS3, a skilled barista can produce shot after shot of a coffee that all taste the same. This is a very, very significant change. By turning some of these variables into at least near-constants, the learning curve when it comes to understanding espresso becomes exponentially quicker. And, of course, evaluation of coffees truly becomes easy.
Most of his comments from that writeup still hold true today. The goal of this review is to summarize the updates to the GS/3 since then and add my own perspective as a home barista.
Dan Kehn

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#3: Post by HB »

Collectively the grouphead, piping, and boiler are referred to as a "group". The portafilter locks into the grouphead; both must be maintained near the desired brew temperature. Some espresso machines have active heaters in the grouphead itself (e.g., Bezzera Strega), some have two legs of tubing that create a thermosyphon to circulate water between the boiler and grouphead (e.g., Quickmill Anita), some have the grouphead attached to the boiler so heat is transmitted from one to the other via conduction (e.g., Rancilio Silvia).

The La Marzocco relies on a saturated group design to minimize the difference between the boiler temperature and the grouphead temperature, which lends itself to more stable, predictable temperatures. I elaborated on this point in another review:
HB wrote:The [La Marzocco] Strada's temperature controls are accurate with no fussing required. This point may initially seem esoteric, but it's worth understanding because potential owners may assume that because a digital readout says the brew temperature is X versus X+2, the actual brew temperature is 2°F warmer. In the Strada's case, that assumption is demonstrably true. That isn't necessarily the case for small boiler espresso machines equipped with PID controllers because they have significant deltas between the boiler temperature and the final brew temperature. For example, a PID'd Rancilio Silvia has a 29°F delta and the Quickmill Silvano has a 25°F delta; the Strada's delta is around 3°F. That's why small boiler espresso machines flash boil for a moment when they've been idle for a long time, i.e., the boiler temperature is above the boiling point of water, so its water becomes steam when it exits to atmospheric pressure. Because of the small boiler and lack of preheating for incoming water, the small boiler's temperature drops dramatically whenever the pump turns on. But thanks to the group's thermal inertia, the final brew temperature is just stable enough for the short period an extraction requires, if-- and it's a big IF --the barista manages the brew temperature carefully.

By paying attention to flush amounts, warmup flushes, production pace, etc., a home barista can operate the small boiler espresso machines within its operational sweetspot and produce consistent espressos. These various workarounds aren't necessary with the Strada. It's simply hassle-free. Greg Scace said it best years ago:
gscace wrote:I think that the holy grail in espresso machines is to make them transparent, so that intimate knowledge of machine use is not required, and so that the focus can be completely on the coffee.
This preamble leads us to the explanation of the origin of the GS/3's name. As noted on La Marzocco's website, GS, in Italian, means "gruppo saturo" or saturated group. The photo below shows a cutaway La Marzocco grouphead from a Linea:

From Cutaway of La Marzocco saturated grouphead

The group above attaches directly to the boiler. The gooseneck shape naturally creates a thermosyphon that circulates water from the (hotter) boiler to the (cooler) grouphead and back. I calibrated the evaluation GS/3 upon arrival using a Scace thermofilter; this step involves drawing water through the grouphead at random intervals to confirm the displayed reading matches the actual brewhead temperature. There's always an expected delta, i.e., the boiler temperature will be slightly higher than the grouphead temperature because the latter is constantly shedding heat. In the GS/3's case, this delta was a mere 1.8°F, which means it's a lot easier for the PID respond to temperature changes measured at the boiler since its reading lags only slightly behind the actual brew temperature delivered at the grouphead.
Dan Kehn

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#4: Post by HB »

The GS/3 is available in two models; the MP (paddle) and AV (volumetric dosing). The paddle model allows you to control preinfusion by pushing the paddle to the midpoint, before the pump engages, to open the brew path. If the GS/3 MP is plumbed in, pressure is provided by the inlet source, either mains pressure or a bottle pump like the Shurflo Flojet. If the MP isn't plumbed in, preinfusion pressure is provided by the steam boiler. Once the paddle passes the midway point, the pump engages and the brew pressure quickly rises to the pump's bypass setpoint (e.g., 9 bar). In my experience, up to 6 seconds of preinfusion noticeably decreases the likelihood of channeling. For the evaluation unit I tested, inlet pressure was set to approximately 3 bar.

The La Marzocco GS/3 has been subjected to exhaustive testing by reviewers and online espresso enthusiasts, but that didn't prevent me from confirming yet again the consistency of its brew water temperature. I didn't bother with the rigors of the WBC test protocol, instead satisfying myself by measuring the effective brew temperature after various idle intervals:


The display above shows tenths of a degree Fahrenheit; over the course of electronic temperature controller's pulsing of the heating element, the temperature oscillated approximately 0.3°F around the desired setpoint of 199.0°F. During the subsequent brew temperature measurements with the Scace thermofilter, the actual temperature mirrored the displayed temperature within the same 0.3°F, with or without flushing! This level of no-fuss, no-guessing temperature control is truly impressive; it frees the barista to focus on dose, grind, and most importantly, taste!

One feature I really appreciate is "quick keys":


Want to increase the brew temperature? Simple, press FN+Key 2, then the +/- keys. Same for the steam boiler. Before wrapping up this review, I'll measure the time required for the brew temperature to stabilize to a new setting using a Scace. My guess is that 3 minutes + 1 flush + 2 minutes should suffice for a 1.5°F increase and probably a couple minutes more for a temperature decrease (again, to be confirmed).
Dan Kehn

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#5: Post by HB »

It's been over 8 years since the La Marzocco GS/3 was introduced in the United States. Bloggers and online forums have documented various issues early adopters experienced. With the assistance of Scott at La Marzocco, below are some of the problems identified and corrected since the GS/3's introduction:
Scott Guglielmino from La Marzocco USA wrote:Problem: Pump buzzing noise on original GS3's braided line.
Solution: Starting at serial number 831, a coupler was placed between the pump and motor, which eliminates the noisy pump issue.

Problem: Gicleur valve frequently clogged.
Solution: The problem of the frequently clogging gicleur arose from poor water conditioning during testing. This problem has been addressed by improving water quality during build and testing. The gicleur was and remains a 0.6mm orifice; this size has been found to create the highest quality coffee. It additionally allows the pump on preinfusion system to operate correctly.

Problem: Vacuum breaker valve too close to back panel touching panel and not properly seating.
Solution: Made adjustment and added silicon tubing over so pin could not touch back panel. Starting at serial number 1170, a plumbed vacuum breaker was installed to prevent further damage if a steam boiler were to overfill.

Problem: Steam and hot water arms mounted with a plastic or teflon piece to the frame was breaking.
Solution: Only the first 25 GS/3's sold in the united states had the plastic steam wand mountings. All known plastic steam wand mountings have been replaced free of charge.

Problem: Water dripped off driptray and onto the countertop.
Solution: The driptray cover pattern was changed in 2010.
A few other GS/3 updates are mentioned on pages 15-23 in this various product updates, excerpted below for easy reference:
La Marzocco - Out of the Box - Various Updates wrote:GS/3 UPDATES #1







While not explicitly mentioned above, it's worth noting that today's GS/3 comes standard with a "no burn" steam wand. It has a teflon tube insert that reduces the heat transferred to the steam wand. Optionally, you can order a standard commercial wand like on the Strada or GB-5 (informally referred to as the "burn me" wand). I haven't installed the burn me wand yet since my impressions of the standard one are quite positive.

If you own a La Marzocco espresso machine, your vendor is your first point of contact if service is required. La Marzocco USA and their network of vendors support cafes all over the country, so its possible to arrange onsite service if desired. Additionally, La Marzocco maintains helpful support pages, including tech bulletins describing known problems and their solutions as well as product updates.
Dan Kehn

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#6: Post by HB »

Among amateur baristas, the speed with which commercial espresso machines steam milk may seem intimidating. The GS/3 steams milk for a cappuccino in around 15 seconds. That's certainly fast, but as you'll see in the video below, even a self-proclaimed newbie mastered it with a little instruction and less than 30 minutes of practice:
From Newbie Introduction to Espresso - Latte Art

The faster speed time is especially advantageous when serving a line of latte lovers because you can finish steaming a pitcher of milk as the pour ends, wasting no time between rounds.
Dan Kehn

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#7: Post by HB »

Many online comments I've read about the La Marzocco GS/3 emphasize its temperature reproducibility; there's less discussion of the machine's impressive capacity. I learned this first-hand at an event where I agreed to serve espresso/cappuccinos at a car dealership that Phillip "the newbie" Marquis works at.

The sales manager told me they expected 20-25 people over the course of two hours. In the end, the turnout was double his estimate. For a home barista used to serving no more than 4-6 people in a session, it was quite a surprise to have 8+ orders waiting for my attention. I quickly came to appreciate the time-saving speed techniques mentioned by pros visiting this board, even if I applied them less fluidly than I care to admit (e.g., strikeoff dosing, wipe work area after each drink, separation of milk/coffee towels).

What impressed me about the GS/3 is how effortlessly I was able to pull drink after drink with nary a thought about flush routines, recovery time, etc. Plainly stated, whether serving under heavy load or serving stragglers at the end of the event, every time I glanced at the brew temperature, it was holding steady within 0.4°F of the setpoint. Coupled with a steam time of 15 seconds for a cappuccino, it was easy to start the extraction and have enough time to finish steaming before it was time to end the shot. This level of speed and consistency was something I expect from the two-group on my espresso bar, but the GS/3 packs similar capacity in a portable (albeit heavy) package.

To better understand how this level of brew temperature consistency under load is accomplished, I've reproduced the graphic from "Update #4" mentioned earlier:

Mixing valve for preheating incoming water (emphasis added)

The long red loop to the left shows the heat exchanger; it acts as a preheater for incoming water. So, instead of water entering the boiler at room temperature, it enters already heated by the steam boiler. What's new since the original GS/3 was introduced in 2005 is the mixing valve shown in red near the bottom right. It has two inputs, unheated water from the mains (or reservoir) and water preheated by the heat exchanger. The gicleur shown in green regulates the mixture ratio so the final incoming water to the brew boiler is closer to typical brew temperatures instead of potentially superheated water. As a result, there is less temperature fluctuation, less need for PID reactivity, and the group has less trouble doing its job - keeping the system at the same temperature.

For my gig as a catering barista, it meant I was free to focus on MY workflow, not catering to the machine's workflow. And that's pretty amazing.

Details from steam boiler assembly diagram; see parts 12-18
Dan Kehn

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#8: Post by HB »

Thanks to the GS/3's impressive brew temperature reproducibility, it's easy to explore how a coffee's taste profile changes by bracketing. My favorite temperature brackets are the three settings 198°F (low), 200°F (medium), and 201.5°F (medium-high), though some who don't like high acidity may wish to shift this range to include +202°F. This strategy can yield interesting results, especially for single origin espressos:

Intelligentsia Black Cat Project - seasonal coffees

The GS/3 requires around 3 minutes to stabilize after an increase in brew temperature (i.e., approximately one minute to reach temperature, one quick flush, then another two minutes to stabilize) and a little longer if decreasing the brew temperature.

For the Piata Bahia Brazil, the chocolate notes sharpened with the increase in temperature; the higher temperature also prompted an interesting shift in the aftertaste. I mentioned this effect at last week's get-together at Counter Culture Coffee and asked attendees how they used temperature to fine tune their espresso. Ian and Lem said they treat temperature as a means to control acidity levels. I agree, although I also find that in addition to a drop in acidity with an increase in temperature, some coffees improve in complexity. I'll look at this question again before closing out the review.
Dan Kehn

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#9: Post by HB »

Please excuse this brief interruption of the review reporting to share some thoughts on the perfect drink for the summer season...

When I first started making espresso-based drinks at home, I drank cappuccinos and an occasional espresso. Later my habits leaned more and more towards espresso; eventually I settled into a nearly espresso-only routine, drinking a mere 2-3 cappuccinos a month. Prompted by last year's Summary of iced coffee brewing methods hosted at New World Cafe, summer now marks the season for espresso served over ice and milk:


I've read concerns that "shocking" the espresso will lead to bitterness, but I've never noticed a problem (our group taste results of rapidly cooled vs. slow cooled espresso didn't point to a clear winner).
Dan Kehn

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#10: Post by HB »

When someone who's unfamiliar with making espresso at home asks me about budgeting for equipment, my response is frequently greeted by an incredulous gasp. I understand their reaction because espresso gear-- for them --isn't what I call a "rare air" purchase. That's the type of purchase where budget is a distant concern, well behind considerations like performance, capability, and the sheer pleasure of operating a top-notch piece of equipment. Chris elaborated on this point in his review of the GS/3 Prototype:
Chris Tacy wrote:So who would buy a GS3? Well... when it comes right down to it, I think that the vast majority of these machines will probably be bought for commercial or semi-commercial use. By this I mean that they will be bought by roasters for tasting, evaluation and training. They will be bought by small coffee bars. They will be bought by caterers and by restaurants.

But some individuals will consider buying one for home. So who, in my opinion, should consider buying a GS3 for their home?

I figure there are probably two groups of home users who should consider the GS3. The first group is the seriously obsessive home espresso freaks... If you are the kind of person who is passionate about coffee and wants to truly understand espresso as best you can - cost be damned - then the GS3 is your dream machine. And if you can afford it, you should buy it. It will free you to truly explore the boundaries of your abilities and your understanding. The second group are those who have more than ample funds, love coffee and simply want a very, very good cup of espresso every morning without too much muss or fuss...

At the risk of insulting people, I'll also point out a couple of groups who should not consider the GS3. First and foremost are those who think that the machine should do the work for them. While the GS3 is incredibly easy to use, you still have to have a great deal of skill as a barista if you want to make great espresso. An unskilled barista using the GS3 is unlikely to produce good coffee. Ever. As with any other espresso machine, the GS3 is a tool for the barista. If you don't know how to use it... you're going to be out of luck. For these people, it is going to be exceedingly frustrating to spend this much money and not have great coffee. The second group are what I would describe as the passionate engineers (also known as tinkerers). For these folks, the process of modifying and improving the espresso machine is at least as enjoyable as drinking the coffee made from it. The GS3 is going to be a mistake for these individuals... [because] improving on the performance of the GS3 is likely to be frustrating, time consuming, produce limited results and be very expensive.
Chris Tacy's review was written before the GS/3 was generally available, but his points on who should consider such a "rare air" purchase still holds true today, especially given that today's GS/3 is even better than the one he reviewed back in 2005. While I was at the last SCAA conference in Boston, I took the opportunity to individually ask Scott Guglielmino (La Marzocco), Bill Crossland (formally of La Marzocco USA, now Crossland Coffee), and Chris Nachtrieb (Chris' Coffee Service) to describe the target demographic for the GS/3. They described the typical GS/3 buyer as someone who:
  1. Has ample funds to pay for it,
  2. Expects precise control of the espresso-making process, and
  3. Appreciates and is willing to pay a premium for uncompromising craftsmanship.
The last two points really encapsulate Greg Scace's idea that the holy grail of espresso machines is transparency, i.e., when the equipment is so consistent, predictable, and easy to use that it fades into the background so the focus remains solely on appreciating coffee.
Dan Kehn