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Cool Beans


Aug 2023

The history of coffee provides a rich index of global economic and cultural exchange going back thousands of years. In the twentieth and twenty-first centuries, we’ve seen distinct “waves” of change in coffee consumption. Not only have roasting and brewing methods grown more refined, tools and accessories have also become increasingly precise in their engineering.

The First Wave marks the emergence of pre-ground, mass-produced coffee (think Folgers), while Second Wave introduces specialty coffee chains and espresso culture (like Starbucks). Third Wave delves into coffee as an artisanal craft, emphasizing bean origin and brewing methods (Blue Bottle, etc.). The emergent Fourth Wave pushes boundaries with scientific precision and sustainable practices, refining coffee’s production and enjoyment.

Our Neptune industrial CT scanner is the perfect companion for tracing this evolution, revealing how and why coffee tools and techniques stand the test of time.

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Moka Express

Bialetti, 1933

Until the 20th century, coffee was primarily enjoyed in coffee shops. That all changed when Alfonso Bialetti invented the Moka Express in 1933, inspired by a washing machine his wife used to do laundry. But the Moka didn’t really catch on until after WWII, when Alfonso’s son Renato refined the octagonal Art Deco design to maximize heat capture in the base and replace the flammable wooden handle with a modern Bakelite one.

More importantly, Renato was a marketing genius who innovated advertising techniques in the 1950s to include billboards, commercials, and even animations — introducing “l’omino coi baffi” (the little man with a mustache), based on Renato himself. The little man appeared on the side of the Moka pot and also starred in cartoons showing how quick and easy it was to make coffee with the Moka Express: all you need is water, coffee, and fire to brew espresso-style (it’s not quite espresso) coffee in the comfort of your own home. Since then, an estimated 300 million Moka pots have been sold, and today you can find them in 90% of Italian homes.

The Moka Express consists of three primary cast aluminum parts: a bottom chamber for water, a middle funnel-shaped filter basket for coffee grounds, and a top chamber to collect the brewed coffee.

To brew, fill the bottom chamber with water up to just below the safety release valve in the wall. Then add medium-fine ground coffee (slightly coarser than you’d use for espresso) to the filter basket, but don’t tamp it down. Screw the top chamber back on and place on a stovetop at medium heat. Be careful to avoid an open flame going beyond the edges of the base, otherwise you’ll end up with a stalactite of melted plastic at the end of your handle — as you can see in this well-loved Moka pot that we scanned. 

As the water heats up, it creates steam. The steam pressure forces the hot water up through the coffee grounds in the filter basket and into the top chamber. Take it off the heat before the volcanic sputtering phase at the end; this only adds bitterness to your coffee.

The aluminum components prove to be pretty hearty, and if you don’t use abrasive cleaners, the Moka pot develops a coffee patina that some believe enhances the flavor. The gasket around the filter basket wears out over time and will eventually need to be replaced. Here you see how the rubber has dried and cracked, making a secure seal impossible. Steam and water would escape, resulting in an incomplete extraction.

Renato Bialetti died in 2016 at the age of 93, and his ashes were interred in a giant Moka pot. Not long after, Bialetti declared bankruptcy but managed to stay afloat after consolidating their business and securing loans. They moved some of their manufacturing outside of Italy, and our CT scans make us wonder if the new Moka Express that we bought on Amazon is a counterfeit or if the quality of the product has fallen off in recent years. Let’s take a look.

We didn’t need a CT scanner to observe grease around the threading and unwanted aluminum shavings in the lower chamber, but cropping into the center column, we see an uneven surface finish with aluminum debris that hopefully wouldn’t find its way into our coffee.

The quality of the casting in this piece is also inferior. Cropping into the walls, we find the new Moka pot riddled with porosity. These tiny voids in the aluminum may not represent a problem for the performance of the brewer, but they suggest that changes to the casting process or the use of new suppliers may have had unintended consequences. The old Moka pot had visible flash inside the lower chamber from where the pieces of the mold came together, but there’s none to be seen in the new one. Even if Bialetti isn’t what it once was, the Moka pot is here to stay as a beloved brewing technique and icon of industrial design.

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Aerobie, 2005

The AeroPress was invented by Alan Adler, a retired engineering professor and coffee enthusiast, and introduced to the world in 2005. Unlike traditional brewing methods, the AeroPress utilizes a unique combination of air pressure and immersion brewing, delivering a smooth, rich cup of coffee in under a minute. Its ease of use and portability made it an instant hit among coffee lovers and travelers alike. Over the years, the AeroPress has garnered a devoted following, inspiring coffee championships and daring experiments with brewing techniques.

The AeroPress consists of two main parts: a cylindrical chamber and a plunger with a rubber seal. To brew coffee with the AeroPress, you place a paper or metal filter inside the bottom of the plastic mesh filter chamber (on the top in the visualization at left). You then add coffee grounds on top of the filter and pour hot water into the chamber. Give the coffee and water mixture a stir to ensure even extraction.

Once the coffee has steeped for the desired amount of time, insert the plunger into the top of the chamber. Gently pressing down on the plunger creates air pressure that forces the brewed coffee through the filter and into the cup below. You can adjust the plunger’s pressure to create different coffee strengths and flavors, allowing full customization.

The silicone seal gasket wears down over time, but not as much as you would expect from this seven-year-old AeroPress. Cropping into it from the side, there’s a 0.5 mm gap that we can measure in our Voyager analysis software. Removing used coffee immediately after brewing and storing the AeroPress with the seal pushed all the way through the chamber (as shown) can help minimize wear by reducing compression to extend the gasket’s life. 

Now let’s compare our old AeroPress to a brand new one.

The densities of the old AeroPress chamber and plunger were very similar, both appearing light green in our color map. The chamber of the new AeroPress, however, is made of lower density plastic, which shows up as darker in our color map. Perhaps this change in material will lead to reduced wear over time for the plunger. Though the original AeroPress was made of clear polycarbonate, the company switched to using BPA-free copolyester in 2009 and then in 2014 they changed to (also BPA-free) polypropylene — a durable but lightweight thermoplastic. The density shift evident in our comparison scans is the difference between the copolyester and polypropylene models.

If you’re an AeroPress user, dealing with leaks or drips during brewing can be frustrating and messy. Loose or improperly sealed filters and caps are common culprits that can allow water to escape. Another cause is using water that’s too hot, which can lead to plastic expansion and gaps. To avoid leaks, ensure the filter is securely placed and the cap is tightly screwed for a proper seal. Using a slightly coarser grind size can alleviate pressure and reduce leaks. Optimal water temperature (175°F to 185°F) minimizes plastic expansion and potential gaps, helping to ensure a leak-free cup of coffee.

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Gooseneck kettle

Fellow, 2022

The gooseneck kettle gained recent prominence with the rediscovery of mid-century pour-over brewing methods, such as the V60 and Chemex, which require precise control over water flow and distribution. The long, slender spout of a gooseneck kettle allows you to pour water in a slow, controlled, and circular motion. An even saturation of the coffee grounds promotes consistent extraction and ultimately a well-balanced and flavorful cup of coffee. The gooseneck design also helps prevent splashing, ensuring a mess-free and enjoyable brewing experience. Fellow is at the top of the gooseneck game with their Stagg EKG electric kettle line. Let’s see how they manage to achieve unmatched precision in temperature control with our CT scans of both the kettle body and base.

With a sleek minimalist design, the Fellow Stagg kettle combines both form and function. Its precision-pour spout has a stainless steel fluted tip that provides optimal control of water flow. Cropping into the counterbalanced handle, we discover the dense embedded weight that shifts the center of mass closer to your hand and makes it easy to maintain a steady stream of water while pouring.

Notice the recessed edge around the circumference of the kettle body base. This increases the surface area exposed to the heating element and speeds up the formation of the convection current to evenly distribute heat throughout the kettle.

With the powerful 1200 W heating element (the thin coil wire), the kettle reaches optimal temperature very quickly — in under three minutes. Hidden in the base, we also see a thermal cutoff switch, a mandated safety device that helps prevent fires by interrupting electrical current when the temperature exceeds a certain limit. If you peek into most kettles, you’ll also see a temperature sensor poking its head up. This “boil-dry protection” automatically shuts off when it detects that the water has evaporated or the kettle has been left empty for too long. In the center we see the copper rings that link up with the base coupler.

But the base is where the magic really happens. In the lower left corner is a small LCD temperature display screen. On the lower right is the main button and dial. There are two toggle switches on the back. On the left, you can switch between Fahrenheit and Celsius (F/C), and on the right, you can set the kettle to hold a temperature for up to an hour. There’s also a hidden game in the Stagg EKG and Corvo EKG kettles. If you remove your kettle from the base and toggle the F/C switch back and forth, you’ll unlock a snake-like game called Wormy that you can play using the dial.

Decreasing the opacity of the lower-density snap-fit plastic exterior, we have an excellent view into the kettle base’s internal circuitry. There’s a cable strain relief entrance at the top that keeps the power cord safely connected to the device. The larger wires we see here deliver 120 V household current to the heating element. The smaller wires power the digital electronics (screen and dial).

The Fellow EKG Stagg kettle features a sophisticated PID (Proportional–Integral–Derivative) controller that uses a solenoid relay switch and MOSFET (metal-oxide-semiconductor field-effect transistor). Instead of kicking on and overshooting the target once the temperature has fallen well below it, the PID controller’s non-mechanical approach ensures uniform heating and precise temperature control with minimal fluctuations (±0.3° C). The solenoid relay and MOSFET work in series; the MOSFET flutters to modulate power supply to the heating element inside the kettle. Departing from basic on/off mechanical relays — the annoying click sound that other kettles make — Fellow’s advanced system employs Pulse Width Modulation (PWM) for gradual power adjustments.

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Burr grinder

Porlex, 2018

The scientific precision characteristic of the Third and Fourth Wave of coffee culture places a premium on grind quality. Blade grinders, like in a blender, chop coffee beans with their sharp edges and get the job done quickly, but they produce grounds that are uneven in size and shape. Burr grinders offer a more consistent and precise grind size compared to blade grinders. They use two serrated components, known as burrs, to crush the coffee beans to a uniform size, resulting in a more even extraction during brewing. Burr grinders also generate less heat than blades during the grinding process, minimizing the risk of overheating the coffee grounds and preserving the delicate flavors and aromas.

This handheld burr grinder made in Japan by Porlex is perfect for on-the-go brewing, making it a great companion for an AeroPress. The stainless steel body holds 40 grams of coffee in the hopper. Instead of twisting the body like a pepper grinder, you crank the handle like an old-fashioned coffee mill to turn the internal conical burr, while the external ring burr remains stationary. Ground coffee collects in the bottom chamber, and you disassemble to retrieve it. You can see we missed a few grounds on our last cup of coffee; there are remnants in the bottom right of the chamber.

Conical burrs allow for a wider surface area, which leads to a slower and more controlled grinding process. Compared to flat burrs, conical burrs also create a more uniform particle size distribution, reducing the potential for clogs and jams. Porlex grinders use high-quality precision-milled ceramic materials. Ceramic remains sharper for longer than steel, does not rust, and imparts no metallic flavor to the coffee. Ceramic burrs have high thermal capacity and don’t warm the coffee during grinding. All of the advantages a burr grinder has over a blade grinder are taken to their highest level with ceramic burrs.

Burr grinders also have the advantage of unmatched precision in their ability to adjust grind size to suit different brewing methods. We compared our six-year-old Porlex grinder to a new one, and discovered a redesigned ring burr with additional teeth. Instead of the original six, there are now 15 steps of adjustment. Each click on the adjustment ring under the burrs changes an average of 37 microns, allowing you to dial your exact specifications for everything from cold brew to espresso.

We also compared the tiny lower teeth and found no detectable wear and only a slight misalignment between the burrs on the used grinder. Despite the somewhat labor-intensive nature of this analogue tool, the quality of its materials and construction allow it to outperform newer technologies.

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