Espresso Research and Engineering

The art of making the perfect espresso drink is an engaging and interesting problem to solve. From engineering the perfect espresso machine, gathering data such as bean grind size/weight/distribution, water type/volume, and managing the pressure in the group head at different stages in the extraction process; your 1-2 ounces of espresso requires careful consideration to nail the perfect shot. In addition, the dexterous art of pouring the perfect drink is challenging and satisfying when successful. One must make sure to position of the milk pitcher/cup correctly, manage flow velocity, properly homogenize your liquids, and use specific techniques that make pouring feel more like working with a canvas and brush.

It wouldn't be an exaggeration to say I love espresso drinks. They're delicious and everything about them is so pretty, the rich dark crema, the art, the stainless steel machinery and ceramic cups. I've been roasting beans, buying roasts directly from local roasters, making roast blends, brewing espresso, and making hearts, leaves, and rosetta art on single/double shot lattes/cortados multiple times a day, every day for the past few years. In addition, I've been dabbling lightly in homesteading dairy cows and growing coffee plants, though not enough to get a drink yet!

Do you folks like coffee? Real coffee, from the hills of Colombia? ~ Duncan Hills Coffee Jingle (Deathklok Season 1 Episode 1)

The following are a summary of my notes on crafting espresso drinks, from the engineering to the dexterous art that goes on top. Crafting drinks and engineering the tools to do so is a passion a sizable group of people share, so please take a look at the references and additional resources for more contacts, modifications, and tools.

Drinks

A sizable amount of people don't know the names of the drinks they want, and cafes are aware of this. Thus when you order a latte, cortado, flat white, cappuccino, etc. you'll often get the same exact drink. There are definitions for these drinks such as the Instituto Espresso Italiano (IET) Italian Espresso , however, I'll provide a definition based on what most baristas and roasters local to the United States agree on.

Espresso

Espresso is normally a single ounce for a single shot (or 2 ounces in the case of a double shot) of concentrated coffee brewed from an espresso machine. That's a rough definition however, as it's more accurate to craft an espresso based on the weight of the initial dose of grinds. That weight can vary depending on your goals, are you aiming for a stronger more concentrated shot, or one that's lighter?

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There's a wide range of flavors that an espresso can have, from sweet and fruity to sour and bitter, and depend heavily on how how the shot is pulled extracted and the beans you choose to use. Generally a shot should be a ratio of 1:2, so for every gram of espresso grinds, you extract 2 grams of espresso. This also tells you how big your portafilter basket should be, enough to accommodate your intended amount of espresso.

With coffee beans, the fresher the better, and light to medium roasts tends to have the most floral flavors, and dark roasts tend to have the more caramel and bitter flavors.

Extraction refers to the process of making a shot of espresso. When pulling a shot of espresso, your compacted grinds go through the following brewing steps:

1. Pre-infusion is when you soak your espresso puck with low pressure water to start your extraction at generally 1-3 bar of pressure. Once the puck is fully immersed in water, we can begin extracting at high pressure.

2. Infusion is when you're pushing high pressure water through the puck. 9 bars of pressure is the standard for espresso, but lever action machines can have a curve of pressure.

Clive coffee goes into more detail here on pre-infusion here.

As for types of espresso, these include:

• Ristretto - typically 40 grams or 1.4 oz. A short shot of espresso, made of only the first portion of a shot, and is thus more flavorful.

• Turboshot - a fast espresso drink that's shorter than the typical 25-35 second extraction.

• Lungo - A longer shot where more water passes through a shot.

Latte

A Latte can vary greatly depending on what you're looking for. The cup its served in generally determines what you get to drink, with 12 oz cups being the standard, and 8 oz cups being an alternative size. As much as the cup is advertized as a given size, it's real capacity is often more than its size. Some 6 oz cups hold 8.5 oz max. Some 12 oz cups hold exactly 12 oz max. Usually the standard is 12 oz exactly.

• A Flat White is a drink with very little to no foam, so little to no stretching of the milk, and only frothing/heating it. In spanish communities, a Cafe con Leche is very similar to a flat white, but uses 2-3 oz of coffee instead of an ounce of espresso.

• A Cortado is A 6 oz drink with 1 oz of espresso, and 5 oz of steamed milk. It's a concentrated beverage, and essentially half of a 12 oz latte.

• Cappuccinos are often interchangeable with a latte, but have significantly more foamy milk, and often have a layer of white foam on top, garnished with powdered chocolate and even decorated.

Latte Art

It's possible to draw anything on top of your espresso drink, even going so far as to print art on top of a given drink. You could do use a stencil with a chocolate powder dispenser, or use a stainless steel latte art pen to adjust your art, but for the most part that's very easy. The challenge with latte art is only using steamed milk to do it.

Texturing

Getting the perfect milk texture is paramount to successfully doing latte art. Generally you want to let the milk naturally disable the "ripping" sound, by forming a layer of foam at a medium density for lattes, with lower/higher amounts of stretching depending on if you're aiming for a flat white or cappuccino. This can vary from machine to machine, and is ultimately driven by your steam wand pressure.

When pouring, maintaining a constant flow and reasonable velocity is very important, that is, approximately 3 fluid oz per second.

• Stir your espresso and swirl your steamed milk well to make each more homogenous. You'll find the best parts of your espresso at the bottom of the liquid.

• Pour from above to establish your base. You may want to add some chocolate powder prior to this for some delicious contrast to the white milk coming later.

• Try resting the spout on the edge of your cup, once you've poured your base. This can offer more control over the pour.

• Pour closely to establish your white art on top, and form a heart by pouring forward, do pulsing waves for a rosetta, and/or restart the process for tulip layers.

Espresso Machines

Espresso machines come at a wide range of prices, from very low to very high. The following is a summary of machines at a variety of price ranges under $6000 USD. Realistically, a good price target that have the majority of important features a barista is looking for is around $1500 USD, and entry level is about $500 USD. Espresso machines can be very expensive, but what matters are specs and performance. A few things to look out for are:

1. What's the heating system? The cheapest machines use thermoblocks, while more expensive machines use heat exchangers and dedicated boiler(s). [Hoffmann 2022]

2. Is it lever based or feature a flow control system? There's 2 schools of thought with espresso, constant or variable pressure, and generally the variable pressure of a lever machine can result in uniquely flavored espresso.

3. How computerized is the machine? Does it feature a PID controller or multiple? Does it feature flow controls, timers, scales, etc?

4. What's the group head size? Usually you want a standard E61 group head, as this is the size with the most accessories.

5. What are the components made of? Plastic, stainless steel, brass, chrome, wood?

6. Is it modable? Anything can be modded to add sensors, replace parts with wood, but some products have more resources and tutorials than others. The Gaggia Classic Evo Pro arduino mod can improve shot profiles tremendously.

Price	Name	Links	Details
$2399.00	Profitec Pro 600	Clive Coffee	E61, Dual Boiler, Shot Timer, PID
$2919.00	Bezzera DUO MN	Whole Love Latte	Flow Control, PID, Dual Boiler
$3399.00	ECM Synchronika	Whole Love Latte	Dual Boiler, PID
$2695.00	Lucca M58	Clive Coffee	Dual Boiler, PID
$2395.00	Quick Mill QM67 Evo	Chris Coffee	Dual Boiler, PID
$2294.15	Bezzera Strega	Whole Love Latte	Lever Action, PID, Single Boiler
$1799.95	Lelit Mara X	Seattle Coffee Gear	L58E Group Head, Dual Boiler
$1850.00	Rocket Espresso Appartamento	Seattle Coffee Gear	Heat Exchanger
$1940.00	Rancilio Silvia Pro X	Rancillo Group	E61 Group Head, Heat Exchanger, PID Controller, 2 L Water Tank
$1725.00	Ascaso Steel Duo PID	Ascaso USA	Dual Thermoblock, PID
$699.95	Breville Barista Express	Amazon	Thermoblock, built in rotary grinder
$549.00	Gaggia Classic Evo Pro	Amazon	Thermoblock

There's other machines at higher price points for the prosumer/commercial market, while there's a very large number of these machines, here's a few:

• Tone Swiss - Arguably the most interesting technologically, Tone Swiss has been working on highly efficient espresso machines.

• La Marzocco - The Gibson of the espresso machine world, La Marzzoco makes incredible espresso consistently.

• Victoria Arduino - This company has been designing espresso machines since 1905!

• Sanremo Coffee Machines - Designing high quality commercial espresso machines with smart features.

There's also other styles of machines such as manual lever press machines.

Components

• Proportional-Integral-Derivative (PID) Controller - Manages the machine target temperature.

• Over Pressurization Valve (OPV) - Manages extraction pressure. Generally low end espresso machines have this set too high, you should aim to have this configured for 9 bars, but this could even be managed by a microcontroller for pressure profiling.

• Grouphead - the mechanism your portafilter attaches to, that holds the spout where pressurized water comes out. The E61 grouphead is one of the more common designs, modeled after the Faema E61.

• Portafilter - The insert that holds your basket and grinds. Most come in 58mm in diameter, while other like the Breville barista express use 53mm.

• Portafilter Basket - The stainless steel basket inside the portafilter. The size and shape depend on the dose you intend to put in it, with double shot baskets resulting in the best extraction.

• Steam Wand - The tool to steam milk.

• Drip Tray - Where excess water gathers for disposal later.

Grinders

Some espresso machines such as the Breville come with a built in grinder, but most do not, so you're required to purchase a grinder separately.

For grinders, what's important is:

1. How fine they can it grind? This is often measured in average particle size. When brewing espresso, the common meme phrase is: "Did you try grinding finer?", and it's true!

2. How quickly can it grind? as a rule, the bigger the burrs the faster it can grind.

3. What's the retention rate of the unit? Does it feature a plasma generator? Bellow to blow air?

4. How computerized is it? Does it have a built in scale? Variable grind size profiles?

Price	Name	Links	Details
$649.00	Turin DF83	Turin	83mm flat burrs
$700.71	Niche Duo	Niche	83mm flat burrs
$989.00	Eureka Oro Mignon Single Dose Espresso Grinder	Clive Coffee	65mm flat steel burrs, single dose design
$959.04	Barsetto E6 Professional Coffee Grinder	Aliexpress	64mm titanium burrs, built in scale
$1299.00	La Marzocco Mazzer Lux D Espresso Grinder	Voltage Restaurant Supply	61mm burrs
$2299.00	Mahlkonig E65S Espresso Grinder	Prima Coffee	65mm flat steel burrs, programmable, 2.6 lb hopper
$2139.00	Weber Workshops The Key	Weber Workshops	83mm flat burrs, all metal build
$299.90	Varia VS3 Grinder	Varia	48m conical steel burrs
$385.00	Femobook A5	Femobook	53mm flat burrs, Compact, Battery Operated

Roasters

Roasting beans yourself can be an extermely effective way of producing amazing coffee. Here's a few high tech roasters:

• Kaleido

• Stronghold

Accessories

For espresso machine accessories, it's important to bear in mind sizes. Check the size of your group head and portafilter prior to getting any accessory. Generally machines have 58mm group heads, but cheaper Breville/Sage machines uses 53mm.

• Portafilter - Can be bottomless, or with different spouts.

• Dosing Ring - A ring used to help keep your portafilter clean.

• Dosing Cup - A cup that can be used to ensure doing weights when serving espresso and keep your grinds clean.

• Filter Paper - a paper that goes on the bottom of your espresso basket.

• Puck Screen - A screen that goes on top of your tamped coffee. Helps keep the group head clean.

• Refractometer - Measure your extraction yield. Generally you should aim for a 20-25% yield.

A few vendors of accessories include:

• Normcore

• MHW-3BOMBER

• notNeutral

• Coffeezone

• Subminimal

• Prima Coffee

• Timemore

Roasters

There's a variety of commercial roasters that ship quality roasted coffee to your doorstep, among which are:

• Onyx Coffee Lab

• Black White Roasters

• The Boy and the Bear Roasters

• Sey Coffee

• HS Coffee Roasters

• Sweet Bloom Coffee

• Presta

• Bigface

• Kurasu

There's large and medium sized roasters such as:

• Counter Culture

• Stumptown

• City Girl Coffee

And depending on your area, you may find great local roasters. Here in Florida there's:

• Buddy Brew

• Foxtail Coffee

• Blazing Bean Roasters

There's certainly more roasters out there, so look for local roasters in your area.

Additional Resources

• Espresso Aficionados

  • Discord

• Barista Hustle

• The Milan Coffee Festival

• Specialty Coffee Expo

• Espresso Parts

• Cropster

• Mtpack

• Roest

• Espresso Setup Builder

Video

• Lance Hedrick

• Emilee Bryant

• James Hoffmann

[Hoffmann 2022] How to Make the Best Coffee at Home James Hoffmann Firefly Books 2022 theworldatlasofcoffee.com