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The Grimac Mia
A Pro's Perspective
By Chris Tacy
About a month ago, Dan Kehn contacted me and asked if I would be
interested in contributing to Home-Barista.com and, if so, what I might
be interested in doing. I jumped at the opportunity and suggested that
I'd love to review home equipment—but from a professional's
While I know a lot about the technology of espresso machines,
fundamentally I'm all about the taste of the coffee in the cup. This is
the perspective I'll be bringing to my reviews. I'm not interested in
data-logging brew temperature or tweaking pressurestats in the abstract.
For me, the machine is a means to an end—the espresso is the goal
and the only valid way to evaluate the product and the process.
I've been a professional barista for years, but have never owned a
home machine or spent any real time using home machines, except for a
couple weeks with a La Pavoni Professional lever machine. One perhaps
unusual consequence of this is that I'm going to be comparing the Mia to
the machines that I am most familiar with, namely high-end commercial
espresso machines. I know this is an unfair comparison, but it should be
illuminating. It's my hope that this somewhat atypical perspective and
slant of these reviews will be both interesting and valuable to readers.
Thanks to Home-Barista.com and espressoParts.com,
my journey into home espresso-making begins with one of the newest
machines on the US market—the Grimac Mia. Grimac is not that well
known in the US, and pretty much unknown in the home espresso world.
They are first and foremost a large manufacturer of commercial espresso
machine components and parts. The Mia is their "semi-commercial"
machine, residing at the bottom of their professional line.
The Mia is a beefy and burly machine featuring stainless steel
chassis, commercial E61 grouphead, and commercial pressurestat. This is
a near-commercial grade of equipment at a materials and construction
level. To be honest, I expected it would be a lighter and more
"toy-like" espresso machine. Instead, I found myself lugging a heavy (in
excess of 50 pounds) and large chunk of machinery into my house. While
this may be a pain when it comes to moving the Mia around, it's a
positive attribute in a serious home machine. It's clearly well-built.
The Mia is a semi-automatic heat exchanger espresso machine based
around the classic and incredibly popular E61 grouphead. This is an
emerging standard combination for a serious home machine. I, personally,
am a huge fan of semi-automatic machines and really would not consider
using anything else. As we'll see later, the E61 HX aspect has its pros
The water reservoir in the Mia has an enormous four liter capacity.
It's quite easy to fill, though the metal cover perched atop the
reservoir seems unstable. I know it looks cool to have the cover act as
part of the "cup tray," but given that it has to be removed regularly
for refilling, I kind of wish that the true cup tray had a rail along
the back and the tippy back section was omitted.
The drip tray is both large and deep. As time went by, the value of
this became very evident. In summary, the highlights of the machine are:
- 4 liter reservoir tank
- 1.3 liter boiler
- 1300W heating element
- Stainless steel chassis
- Commercial-grade pressurestat
- E61 grouphead
- Deep drip tray.
The Mia looks different than the usual "stainless steel boxes" that
seem to dominate the current market. With the formed plastic side panels
and exposed E61 grouphead front and center, this machine screams
"Italian design." I must say, I like it. It's not flashy or overly
styled, but rather clean and well-designed without getting all Bauhaus
Setting up the machine is trivial. You'll need sufficient space: 17"
deep, 12" wide and almost 24" high if you're going to be storing
cups on top. Also make sure that the counter you're putting the machine
on is low enough for tamping comfortably and effectively on it. Of
course, you'll need an outlet nearby, but otherwise all that's required
is filling up the reservoir and plugging it in.
As noted earlier, the Mia has a large reservoir, so you'll want to
stock up on a whole stack of water bottles (in testing I went through
over 30 liters of Crystal Geyser). In addition, because filling the
machine requires the removal of the back of the cup tray, I suggest
either not locating the machine under a cabinet, or double-checking that
you have sufficient clearance to negotiate the refilling process.
Before putting new equipment into service, I always start off with a
thorough cleaning. First, flush about a liter of water through the
machine, and then backflush the machine with cleanser and clear water.
Soak the baskets and portafilters in a cleanser solution and then scrub
the insides of the portafilters with a green scrubby. I wipe and brush
and clean everything that comes into contact with the coffee. And then
run at least a dozen shots through the machine without worrying about
setting grind or tasting anything. Once these steps are completed, I
backflush the machine one last time and then it's ready to go.
Below is the list of additional items you'll need to get started:
- 58mm tamper
- Puro Caff or other espresso machine cleanser
- Bar towels
- Gasket brush
- Burr grinder
There are a few (optional) things that I utilized in my testing,
- Green scrubbies (for cleaning brass)
- Old La Marzocco portafilter
- Graduated shotglasses
- Shot timer
- 16 ounce milk steaming pitcher
- Grounds bucket
- La Marzocco ridged double filter basket
- Triple filter basket.
Although the machine came with a bottomless ("naked")
portafilter, for testing purposes, I also wanted to utilize a standard
portafilter. I've pulled probably a couple hundred times more shots from
a standard portafilter than I have from a naked, so it made sense to go
with what I'm used to. Another reason I chose a standard is my hatred of
new portafilters. The flavor of espresso from a new portafilter is
horrible. There is an awful, artificial brightness and harsh metallic
note that I am convinced comes from the chrome plating. As a result, I
strip the chrome off the insides of my portafilters and then keep the
brass clean, polished and seasoned. To save time stripping the chrome
off Mia's portafilter, I instead sourced a retired and broken-in La
Marzocco portafilter. I soaked it in a Puro Caff solution and then
heavily scoured the interior with a green scrubby before rinsing and
seasoning with a couple garbage shots. I repeated this process every
day, and on particularly busy days repeated it twice a day.
A couple immediate impressions upon setting up this machine. First,
I've always laughed at home users who complain about how messy espresso
is. I take it all back. It's one thing to live with the espresso mess in
a coffee bar. It's an entirely different thing when it's your home.
Second, not having the machine plumbed-in is hard to get used to. It's
very messy. Third, the vibe pump is loud. Seriously. It borders on
ridiculous in fact. Finally, I was disappointed to see that the Mia's
steam wand tip had only one hole. While I've read all about the
purported benefits of such "cheater" tips, I have always had my doubts.
I ordered some additional tips, just in case.
After my first afternoon with the machine, I was really excited. Some
of my worries about living with a home machine were gone. This was a
serious piece of equipment and I was starting to suspect that I was
going to be drinking a lot of good espresso. In addition, I realized
that I was going to be learning a lot—not only about the Mia, but
about espresso and espresso machines in general. Going to sleep that
night was like being a kid on Christmas Eve again waiting for the
It became apparent within the first half dozen shots that the Mia has
some quirks that profoundly affect the life of the barista. These quirks
may be unique to the Mia or they may pertain to home HX machines in
general. It's too early in my study of home equipment to judge for
The biggest quirk is one that I was prepared for—managing brew
temperature. The Mia, like all HX machines, sees a steady increase in
temperature at the group when idle. In order to obtain the optimal brew
temperature for a specific coffee, the barista develops a routine for
not only cooling the group off, but producing the optimal brew
temperature when the shot is pulled and during extraction of the shot.
This routine is commonly known as "temperature surfing" and you can read
detailed explanations of its use (such as How I
Stopped Worrying and Learned to Love HXs on this site).
including . In addition, I've worked on commercial HX machines and have
temperature surfed those machines for optimal brew temperature. Even so,
pulling shots with the Mia was a new experience for me.
I've spent most of my career using commercial dual boiler machines.
With them, there's little need to temperature surf. If the machine has
been idle, a quick flush of the group brings it up to temperature. With
commercial HX machines, you may choose to temperature surf like home
units to obtain the target brew temperature more precisely, but the
variance even when idle is dramatically lower and temperatures change
more slowly. In addition, commercial machines in a café are less
likely to see extensive idle periods. So true home style temperature
surfing was a new experience for me.
I tried several of the common methods, but in the end felt most
comfortable with the methodology that I always used with commercial HX
machines. I would taste a first shot and adjust the flush timing
(performed immediately before pulling the shot) based on the temperature
of that first shot. This methodology probably is not applicable to
typical home usage, as it requires an understanding of how slight
deviations in brew temperature affects a specific coffee and thus
requires a lot of time spent tasting a coffee under many circumstances.
In addition, it requires more time and coffee than most people wish to
expend. On the other hand, it leveraged my strengths, so it was ideal
for me. In fact, when I double checked this method with a thermocouple
thermometer later in the testing period, I found that the temperature
was accurate 9 out of 10 shots after the initial shot.
That said, the reality is that this is just a slight variant on the
standard "water dance" method described in How
I Stopped Worrying and Learned to Love HXs, however instead of
pulling the shot as the temperature is rising, I'm pulling the shot
immediately after it's fallen.
The implications of the requirement that a barista manage brew
temperature are, in my opinion, significant. In the absolute, it means
that a home barista using the Mia needs more skills than a professional
barista using a La Marzocco Linea in order to make one great shot. Of
course, the reality is that a professional barista is not just making
one great shot—there are other requirements of the job. And as I
discovered during this test, a serious professional barista can easily
make one good shot on the Mia. Nonetheless, the skill level demanded by
the Mia to produce exceptional espresso is quite high.
The challenges of brew temperature management were especially evident
when I started training a novice barista on the Mia. While she was able
to pull good shots within the first couple days of training, she had a
very hard time doing so with any consistency, even after the first week.
The principle challenge was the number of variables involved, but in
particular the temperature surfing was never something that became
intuitive to her. Without an understanding of the look, smell and taste
of an espresso whose brew temperature is 1°F too hot, it's
impossible to adjust the temperature surfing timing using the method I
was most comfortable with. As a result, she switched to the water dance
method. This allowed her to be more consistent, though the range of
temperature was still wider than what I was getting. I think this was
probably in large part the result of more variance in the time of the
overall process of building a shot. Nonetheless, this has implications
for a home barista using the Mia. To obtain exceptional results, you
must become a skilled barista who understands the machine and the
espresso or you're going to have a rough time of it. This doesn't mean
you must be able to taste a 1°F brew temperature change, but rather
that you need to understand this machine and learn to work within its
constraints. Now to be fair, my guess is that this statement is true of
nearly all home machines and a very large percentage of commercial
machines as well. Fundamentally, the experience of working on the Mia
taught me one thing above all else—the capabilities of the
espresso machine are rarely the problem.
Other than the temperature management issues, the Mia is an
incredibly usable machine. The ergonomics of the Mia are well thought
out, switches are well placed, easily identifiable and provide excellent
feedback. Everything feels solid, sensible and simple. Working on the
Mia is like working on a commercial machine—with the exceptions of
the temperature surfing and the need to refill the reservoir. The
techniques, the style, being a barista—it's very much the same. If
you have skill and training and an understanding of the realities that
lie behind the espresso machine, you'll be very satisfied. If you're a
seasoned barista, the Mia will make immediate sense to you. Within a few
days I felt very at home with the Mia and was able to apply many of the
techniques, lessons, skills and theories that I had developed from years
on commercial dual boiler machines. In other words, being a barista is
being a barista, regardless of your tools.