Boiler pressure gauge with cooling tower

If you want to capture accurate boiler pressure measurements, you need to have a high accuracy gauge and you need to mitigate measurement inaccuracies related to process temperature effects.

NOSHOK is one of many vendors that provide liquid or air filled pressure gauges suitable for tuning up your Olympia espresso machine’s pressurestat setting. (Their products are available through McMaster-Carr.) As explained in an application note on the NOSHOK website, process temperature can negatively impact pressure measurement accuracy [emphasis added]:

Temperature Influence:

For every 18 °F (10 °C) shift in temperature from which the gauge is calibrated, the user can experience up to a ±0.4% additional error. The cause is the change in the elasticity or spring rate of the Bourdon tube element with temperature. While it is difficult to circumvent the influence of ambient temperature, we can address the influence of process temperature. In steam service, the common practice is to install coil syphons or pigtail syphons to dissipate process heat. Another common practice is to install a diaphragm seal with capillary to separate the gauge from the high heat source. There are many options available with fill fluid in the seal and capillary system to withstand temperatures up to 600 °F. In severe cold ambient conditions, many users elect to heat trace their instrumentation via electric or steam trace. Process and ambient temperature is an important consideration when selecting and applying pressure gauges.

Many people have successfully used 140°F-rated pressure gauges with the Richard Penney boiler neck adapter, as shown here and here. However, some of these gauges are not rated for the process temperatures inside of an espresso machine boiler, which obviously exceed 212°F. Further, the gauges themselves are generally installed in close proximity to the boiler, which will tend to compromise measurement accuracy. If you are willing to spend the extra money, it is possible to address these issues through gauge selection and measurement device configuration.

As a general rule, all-stainless steel pressure gauges are rated for higher media temperatures than gauges with brass parts. For example, this 2-1/2-inch 30-PSI WIKA gauge from Valworx, which is shown in the photo above, has a stainless steel case as well as stainless steel wetted parts; it is rated for media temperatures up to 212°F and ambient temperatures of 140°F. Best of all, its mid-scale accuracy is 1%, which means it is ideally suited for capturing accurate boiler pressure measurements—provided you can address the negative impacts of elevated process temperatures.

You can address process temperature impacts in Olympia espresso machine applications by installing a cooling tower or diaphragm seal or similar between the Richard Penney boiler neck adapter and your pressure gauge. In the photo above, I am using a Model A-240-A perforated cooling tower from Dwyer to moderate process temperature effects. This cooling tower is basically a heat sink that pulls heat out of a small-diameter pipe spiraling up inside the perforated tower. During a typical boiler gauge pressure measurement, the base of this tower is too hot to touch with a bare hand; however, the top of the tower is only warm to the touch.

By taking these extra steps, you can capture accurate boiler pressure measurements on your Cremina. Note that in order to ensure measurement accuracy over time, you will also need to protect your pressure gauge against the vacuum that the boiler pulls during cool down. To do this, simply open and close the steam wand periodically as the machine cools down, in much the same way as you relieve false pressure in the boiler prior to taking any official pressure measurements.

In praise of the “big group” Penney portafilter

While the difference in diameter sounds modest, the 54mm portafilter is nearly 65% more massive than the 49mm version.

At some point in the 1980s or ’90s, Olympia began manufacturing a 54mm group for its heat exchanger espresso machines, which otherwise have a 49mm group like the Cremina manual lever machines. One nice thing about this larger group is that it will have better temperature stability as compared to the smaller group. For example, Richard Penney’s 54mm NEWD portafilter weighs in at roughly 370 grams as compared to roughly 225 grams for the 49mm version.

The downside of having an Olympia Express “big group” espresso machines is that 54mm replacement parts are much harder to find than for 49mm machines. By special request, Richard was able to produce a very small batch—five units—of 54mm bottomless portafilters for Olympia “big group” machines. These large portafilters are almost as rare as hen’s teeth, and they will sell out fast. Get yours at the CoffeeBOS shop on Etsy while supplies last.

R. Penney boiler-neck pressure gauge adapter

Late-model Olympia Express espresso machines—both manual lever and heat exchanger models—incorporate a 2.5-bar boiler pressure gauge. Just because you are rocking a vintage machine, doesn’t mean you can’t have this functionality.

In the summer of 2008, Richard Penney designed a prototype boiler-neck pressure gauge adapter for Olympia Express espresso machines in response to requests from fellow home barista. This adapter mounts on the boiler neck in place of the OEM boiler cap, and is threaded to accept pressure gauge with a 1/4 NPT (National Pipe Thread) mount. In effect, it allow home users to calibrate the pressurestat on their espresso machine in much the same fashion as they were originally calibrated back in the factory. The adapter fits all Olympia-made machines: Cremina, Maximatic, Club, Coffex and the re-branded Pasquini Livietta.

The pressurestat on Olympia espresso machines is mounted under the back cover alongside the boiler. The pressurestat is adjustable via a knurled brass knob, which you can see here:

pstat

Turning this knurled knob toward the boiler increases the pressure (and water temperature) inside the boiler; turning it away from the boiler decreases the pressure within the boiler. (Note that very early Cremina models may have a different pressurestat orientation than shown here.)

In order to set the pressurestat to the factory recommended settings—or to your preferred setting—you need a way to mount a high accuracy pressure gauge on your machine. At the factory, this is accomplished by temporarily installing a pressure gauge on the boiler neck in place of the boiler cap. A technician will then refer to the manometer readings as the heating element cycles on and off, and adjust the pressurestat accordingly.

With the Richard Penney boiler-neck pressure gauge adapter, you can not only ensure that the pressurestat on your vintage espresso machine is set properly and verify its deadband, but you can also optimize the setting to your brewing style. Most people agree that something in the 0.7–1.2 bar range is ideal. However, people who want to steam milk efficiently may want their machine to cycle at the top of that range, whereas some espresso purists prefer to to set their machine at the lower end of this range.

To set the pressurestats on my machines, I purchased a high accuracy 30-psi liquid-filled pressure gauge from Valworx with a 1/4 NPT fitting for $45. This particular gauge is 2.5″ in diameter, has a stainless case and stainless sensing components, and is rated for 212°F media temperatures. (You can find 2% to 3% accurate pressure gauges for under $15, but they my not be rated for 212°F media temperatures.) For good measure, I also installed a perforated cooling tower between the pressure gauge and the Penney adapter. This cooling tower tempers the steam temperature before it comes into contact with the pressure gauge, which improves measurement accuracy and prevents damage due to high temperatures. (Note that you also have to protect the gauge against the vacuum that the boiler draws during cool down by venting the boiler as it cools.)

Armed with my high accuracy pressure gauge, I learned that the pressurestat on my 1991 Pasquini Livietta was set too high, whereas the one on my Cremina was set too low—in spite of the fact that both were calibrated using an inexpensive pressure gauge a few years ago. Now that they are calibrated properly, both machines are brewing better espresso.

If you are tired of brewing blind, check out the CoffeeBOS shop on Etsy to pick up your own adapter!

Cona brew board compatibility

Q: Which vacuum coffee maker models are compatible with the Cona siphon brew board?

A: All of the Cona tabletop models—Models A, B, C and D—are compatible with the siphon brew board for Cona vacuum coffee makers. Of these models, the C and D are still in production, whereas the A and B models are only available used.

While a Model C brewer is shown in the photo above, the Model D brewer uses the same base and handle. Also, the height of the bottom of the globes is identical. So the only difference is the diameter of the globe and funnel—and the brew board design takes these differences into account.

Additionally, the Cona brew board will also fit the smaller Model A and B brewers. While these brewers have a more compact frame geometry, they are still a good fit with the brew board.

Q: Which is the best butane burner for me?

A: It depends. The best adjustable butane burner for your application will depend on which brewer you are using.

The cup or recess in your CoffeeBOS siphon brew board is designed to accept an adjustable butane burner. These burners can be turned on “high” for bulk heating. They can be turned on “low” when the brew water has risen up into the funnel. With a little practice, you will be able to intentionally, accurately and repeatedly manage your brewing temperature within a very tight range.

On the one hand, the Cona brew boards have a 3.5″ diameter cup for the butane burner, which is roughly the diameter of the hole in the base of the brewer. On the other hand, the Japanese-style brew board, like those for the Hario TCA models, have a smaller diameter hole (3.375″) and require a smaller diameter burner to fit within the forks of the brewer. The three butane burners that I own range between 3.125″ and 3.4″ in diameter, and all nest very neatly inside the base of the Cona brewer. However, while I can use all three of these burners with a Cona brew board, only the two smaller burners work with my Hario brew board. These burners are all roughly 3″ tall. 

If you are shopping for a new butane burner, I can personally recommend the Rekrow RK42013 for Japanese-style brewers and the B302 professional grade micro burner for Cona vacuum coffee makers. Both these units put out plenty of heat for larger volume brewers, like the Cona Model C or D or the Hario TCA-5, and are adjustable enough on the lower end to accommodate smaller volume brewers, like the Cona Model A or B or the Hario TCA-3 or TCA-2.

The Rekrow RK4203 is undoubtedly the most common butane burner used for siphon brewing. Since it is often sold with Yama brewers, it is occasionally identified (incorrectly) as a Yama butane burner. Once you pick up this butane burner, you will have no doubt about the quality of its construction. It feels substantial, like it is built to last. The adjustment dial is responsive, and may take some getting used to. When I last looked, Prima Coffee had the best price on this burner. While the Rekrow burner is ideal for use with Japanese-style siphon brewers, it has two shortcomings when used with a Cona brewer. First, the depth of the cup plus the height of the Cona base may not allow provide adequate clearance for the lever-actuated ignitor. This can be solved by lifting or shimming up the burner, but is an inconvenience. Second, the Rekrow burner has a dome-shaped fuel reservoir, the shape of which is not ideal for pinning the Cona brewer to the brew board.

The B302 professional grade micro burner (pictured above) is actually the best fit with a Cona brew board setup, in part due to the push-button ignitor. While there are no manufacturer markings on this burner, Google seems to attribute this burner to the vendor YTC Summit 1234. Based on its shape and diameter, this butane burner likely holds a bit more fuel than the Rekrow. It also has a broad flame head. This is a powerful butane burner in terms of BTUs, which is a nice feature if you have a relatively high volume brewer. While perhaps not equal to the Rekrow in quality of construction, it is comparable to it in terms of performance. Best of all, the fuel reservoir of the B302 burner has steep “shoulders,” and this form factor does a great job of pinning the Cona armature in place atop the brew board. The only real downside to the B302 burner is that its diameter is too large to fit Japanese-style siphon brew boards.

In summary: the B302 burner WILL NOT fit Japanese-style brew boards, but is ideal for Cona brew boards. While the Rekrow burner will fit Cona brew boards, it is best suited for use with Japanese-style siphons, like the Hario TCA models. Therefore, I use the B302 burner exclusively with my Cona brew board and a Rekrow burner exclusively with my Hario brew board. 

Hario siphon brew board in situ

Customer photo of a customized CoffeeBOS siphon brew board prototype.

While most siphons have a chromed base, Hario makes a couple limited edition versions with a gold or copper finish. This TCA-2 has the gold finish as well as a wooden handle. The brew board was customized with a polished brass stand pipe to better match the brewer.

The customer’s initial feedback on the Hario TCA siphon brew board prototype is positive: “Spectacular. Just beautiful, artisan work.”

Custom Hario TCA siphon brew board

Live-edge spalted pecan Japanese-style siphon brew board with a polish brass standpipe.

This Hario brew board prototype was customized for use with a limited-edition Hario TCA-2. The polished brass stand pipe will match the gold-plated finish on the brewer. Pictures don’t do it justice. Both side edges of the brew board are natural live edges. The board has a very sexy splayed profile, kind of a subtle hourglass shape. It looks like the piece was intentionally sculpted by an artist. But it is simply the natural shape of the wood revealed and celebrated.

You can see this brew board in the raw here or check out additional views of the board here.

[SOLD] Vintage gold-plated Cona new table model

New old stock? Display model? The last of its kind?

The date stamp on the base of the brewer indicates that this gold-plated Cona new table model size C vacuum coffee maker was manufactured circa 1985. However, it appears that it has never been used. The spirit lamp is still wrapped up in packing paper and does not smell of alcohol. Further, the brewer is still in the original packaging with the manufacturer’s instructions. The glass was made in West Germany and is absolutely stunning.

ConaC.packaging.web

If you are a serious coffee collector, you may never see a Cona brewer like this one again. And if you are a serious home brewer, here’s your chance to elevate your tabletop coffee brewing to the highest levels of elegance.

Best of all, you don’t have to settle for the binary temperature control offered by the spirit lamp. With a siphon brew board from CoffeeBOS—like the longleaf pine bistro-style board pictured below—you can brew in style while maintaining stable and optimal slurry temperatures.

Cona.Gold.board.web

Coming this fall: Hario TCA model siphon brew board

Construction is complete on the first ever CoffeeBOS brew board for Hario TCA model siphons.

This summer, a Home-Barista member and I will be performing extended usability tests on a pair of CoffeeBOS Hario TCA model siphon brew boards. I just took the first completed prototype for a successful test drive. Later today, I will finish assembling a custom prototype with a polished brass standpipe to match a limited edition gold Hario TCA 2. Production models may be available as early as October. (We’re spending the summer far from the Texas heat, so all CoffeeBOS production is on hold until fall.) The Hario TCA brew board will accommodate 2-, 3- and 5-cup models; the 5-cup siphon is pictured in the lead photo. If you would like to receive a notification when the Hario brew boards go live on the CoffeeBOS store on Etsy, just send me an email: david@coffeebos.com

New BOS (balance of system) component: Richard Penney 49mm NEWD portafilter

Do you have a vintage Olympia Cremina with a missing portafilter? Do you want to master the art of the naked extraction with your vintage MCAL? If so, this is the tool for you.

I purchased my first Richard Penney bottomless portafilter from Orphan Espresso in February 2012, shortly after rebuilding a vintage 54mm group Pasquini Livietta, a heat exchanger espresso machine built in Switzerland by Olympia Express. Not only did it look great, but it also allowed me to diagnose extraction problems and accelerate my progress along the home espresso learning curve. I have used this custom stainless steel portafilter almost every day since, and find it superior to the OEM portafilter in every way. It offers better aesthetics, enhanced hand feel, optimal ergonomics and improved diagnostic capabilities. When I purchased a ’74 Olympia Cremina in October 2012, I immediately ordered a 49mm Richard Penney bottomless portafilter for it as well. However, in the years since, Orphan Espresso has stopped carrying Richard Penney portafilters in all sizes, in part to focus on its successful line of high-end manual coffee grinders.

Since a 49mm bottomless portafilter is a valuable addition to the vintage home espresso ecosystem, CoffeeBOS and Richard Penney have teamed up to keep this naked portafilter in production and available for sale. This product has a 7 year history in the field and is used by hundreds of home baristas. It will fit the Olympia Cremina, as well as the Elektra Micro Casa a Leva. It will also fit heat exchanger machines manufacturer by Olympia Express, provided these have the smaller 49mm group; it will not fit 54mm group models. While the handles in the lead photo are only shown for reference purposes, I do have two lightly used handles—the second handle from the left and another one just like it—available for resale. We will roll out custom CoffeeBOS hardwood handles in the fall.