Let's get to the coffee!
If you've done some initial research, you no doubt have come across the two popular types of espresso machine boiler designs: heat exchanger and dedicated brew boiler (if not, see Espresso Machines 101 for a quick recap). Much of what you'll read will focus on the extra steps heat exchangers require, a ritual known as the "cooling flush." Although dual boiler espresso machines simplify this necessity by dedicating a boiler to maintaining brew temperature, heat exchange machines are not without their own advantages such as:
- Reduced purchase cost
- Less parts means potentially reduced maintenance costs
- Consumes less energy
- Brew water is flash heated, so it's guaranteed to be fresh
- With practice, the barista can make minute temperature adjustments on the fly.
I demonstrated the last point one weekend when Steve Robinson, the Lever Espresso Machines forum moderator, stopped by to check out the Vetrano. He sampled an espresso made from Intelligentsia Kid O's Organic espresso blend. Although he thought the texture was excellent, he noted a sour finish and asked for a retry. Lately I had been toying with borderline low temperatures to favor the "gentler" flavors than are muted by higher temperatures, but who am I to argue? One of the advantages of a heat exchanger machine is that you can tweak the temperatures in small increments by flushing a extra couple seconds (however not with the level of precision reported for the La Marzocco GS3; the last degrees of temperature management on a heat exchanger rely on the barista's skill and intuition). I've noted that Steve favors ristrettos, so I also increased the dosage by settling the grounds with an earlier portafilter tap on the grinder's fork while dosing. The extra grams of coffee slowed the extraction rate, pushed up the crema's creamy texture and amplifed the stronger flavors. The additional five seconds of rebound time increased the temperature just a tad. These two adjustments yielded an espresso more to his liking: Bolder initial flavors, richer crema, even finish— and not a trace of sourness.
Pulling Shots by the Numbers
Below are the steps for making your first espressos. Let's assume that you've adjusted your grinder for a reasonable 25-27 second extraction:
- Allow the group at least 25 minutes to warm up.
An accurate and stable brew temperature relies on the entire brew pathway being up to temperature. Ideally you should do one or more "warmup flushes" to better equalize the grouphead and heat exchanger temperatures after a long idle period.
- Measure out and grind your coffee beans.
I found that 18 grams of coffee beans / a small heaping basket full of grinds worked great (a level basket holds around 15 grams before any settling, depending on the blend). Smooth out the grinds to an even bed of coffee. Once tamped down, the coffee will leave the top of the ridge for the basket retention clip exposed (check out the site's How Tos for more details on properly preparing espresso and diagnosing common problems).
- Draw water through the group with the portafilter in place.
Observe the "water dance" and listen for the hissing of steam and boiling water; this video clip demonstrates a proper cooling flush. Continue drawing about two ounces of water after the stream has settled down. If you've recently pulled a shot, remember that the cooling flush will be considerably less than the full flush amount of four to six ounces.
- Remove the portafilter, fill and tamp firmly with about 30 pounds
Many people underestimate how hard they are actually pressing. The key point to remember is the consistency of your tamp pressure from one extraction to another, not the precise pressure amount itself.
Move briskly, you only have about 30 seconds after the cooling flush before the water reaches your target brewing temperature. (Alternatively, remove the retention clip from the portafilter so the basket drops in and removes easily. Then you can tamp at your leisure while the portafilter remains in the grouphead. Once the basket and coffee are ready, a quick turn to remove the portafilter, drop in the basket, then back in the grouphead.)
The HX Love article refers to the period between the flush and the beginning of the extraction as the rebound time. You can increase or decrease the target brew temperature by adding or removing seconds from this waiting period; each 1°F change corresponds to approximately five seconds within a temperature range of 198-203°F for a boiler pressure of 1.1 bar (e.g., 201.5°F = 30 seconds, 202.5°F = 35 seconds, etc). These are only rough guidelines; you will need to adjust these approximations based on taste.
- Lock in the portafilter and raise the lever to start the
If you will not be preparing another espresso, take a moment after the shot is complete to rinse the grouphead by loosely locking in your second portafilter with a blind basket and running water while slowly jiggling the portafilter handle back and forth. This "wiggle-rinse" will wash most of the loose grinds off the grouphead and dispersion screen and over the sides of the portafilter into the drip tray. Be careful not to splash yourself with hot water! Because the driptray doesn't extend far beyond the reach of the grouphead, place a towel over the front edge to save time cleaning up countertop dribbles.
Remember to relock the portafilter back into the grouphead to keep it warm. At the end of a session, I also recommend a quick water backflush to clear the pathway from the grouphead to the pressure relief valve that empties into the back of the drip tray. Refer to Espresso Machine Cleaning - Why, How, and When for more details on a cleaning regime that applies to the Vetrano.
Whew! If all this talk of listening to cooling flushes has your head spinning, below are Bob Yellin's keep-it-simple rules that work well:
- If the machine has been idle for awhile, flush 6 ounces
- Or, if the machine has been idle around three minutes, flush 2 ounces
- Wait 30 seconds and start the extraction.
That's it! At the other extreme, if you want to push the temperature reproducibility of this espresso machine design to its limits, continue with the next section, otherwise follow the rest of the review with Steaming Performance on the next page.
Developing Better Temperature Control Skills
Many shoppers for high-end espresso equipment are stymied by choices. It's a lot of money to spend and the opinions on the "best" choice vary widely. The Andreja Premium has earned a good reputation since its introduction, but some buyers hesitate to purchase a heat exchanger espresso machine because of the added effort of temperature management compared to dual boilers, despite the hints offered online and in articles like HX Love. In order to master HX brew temperature control, Eric Svendson has done all the legwork to bring us a ready-made package shown to the right. According to Eric, the purpose of this adaptor is to facilitate the measurement of brew water temperature about 1.25" away from the puck during a real brew cycle using the thermocouple and digital thermometer of your choice. It requires no drilling, tapping, soldering, brazing, cutting, Teflon tape, or epoxy. The difference between the temperature that you will be measuring using this adaptor and measured temperature of the water hitting the puck is very close to the actual brew temperature.
My interest in this adapter was not determining the actual brew temperature, but collecting real-time data of the water exiting the heat exchanger to better judge the correct flush amount, independent of how long the machine had been idle. In other words, to answer the question: How consistent are the brew temperatures for those who simply flush the group until the digital thermometer says temperature X? I ran a series of tests using the E61 adapter to judge the correct flush. The measured results are excellent and confirmed by my daily use preparing espresso.
I had already determined that the proper temperature at the well depth for my routine was 206°F before the adapter arrived. Keep in mind that for the purposes of this test, I didn't worry about what the adapter's reported temperature relative to the brew temperature might be, as long as it indicates the same readings every time. I note a very distinct "knee" right around 205°F. The temperature moves slowly prior to that and then plummets just past it. Below are the results of five simulate extractions measured with the thermofilter using this approach:
Irregular pulls (3m, 1m30, 3m, 15m, in no particular order)
- Grouphead is definitely cooler and the HX hotter after the machine is idle for a long period (see the line in red; it rises more slowly at first and spikes higher)
- "Warm up" flush would spike well above the target brew range then settle down (this "high hump" profile was not recorded)
- Adapter feedback made it easy to stay within 1°F, although occasional outliers still occur, especially if interval was short (see blue dashed line with 200.4°F peak temperature)
- The adapter reading and thermofilter reading converge about midway into the shot; the thermofilter indicates a very slow decent towards the end and the adapter is reporting near flatline temperature from the HX (for simplicity's sake, both readings are not shown in the chart above).
The utility of Eric's adapter is plainly evident: By tuning the flush amount based on the adapter's digital thermometer reading, reproducible temperatures are easily obtained within ~1°F. Bob Yellin's simple rule of "flush two ounces if it's been three minutes" described in Pulling Shots by the Numbers works well for that situation, but the adapter enabled me to improve on it with these easy-to-follow steps:
- If the machine has been idle for 10 minutes or more, flush until the readout indicates 206°F. Allow the group temperature to equalize for at least one minute. Note: The empty portafilter should be locked in.
- Remove the portafilter. Dry the basket. Dose, distribute, tamp. Flush until the readout indicates 206°F.
- Lock in the portafilter.
- Wait 30 seconds since the end of the flush in step (2) and then start the extraction; adjust delay to taste as desired in 5 second intervals, usually between 25-35 seconds. This protocol consistently delivered 201.5°F peak brew temperature. Note: Heat exchanger espresso machines naturally deliver a slightly "humped" temperature profile as explained in How I Stopped Worrying and Learned to Love HXs.
In summary, those who worry about the complexity of HX temperature management have a solution that a half-blind one-armed barista suffering from a mild case of AADD could not screw up. I look forward to the day when such a readout is standard equipment on consumer heat exchanger espresso machines. In the meantime, those who wish to push heat exchanger temperature reproducibility to the maximum have a straightforward option.