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Introduction |
It's time to take this espresso machine around the block a few times. As I've already mentioned, the key advantage of the Expobar Brewtus over a prosumer HX machine is the ease and accuracy of temperature control. How important is it? Time to find out in the next section.
To demonstrate the point, I took the machine for an espresso ride. Participating in this jam session were the following espresso blends:
I chose these blends for a specific reason. They all have different optimal brew temperatures, and some, like Vivace Dolce, are very finicky about temperature. If the extraction isn't at precisely the right temperature, you will taste the negative consequences in the cup. It could be dull, sharp, or ashy. Some, like Terroir Northern Italian, are roasted very lightly. Such blends nicely demonstrate the effect of a gradual change in brew temperature from the low end of the scale at 91°C to the high end at 96°C.
Technical notes: For each shot, I measured brew temperatures with an Omega HH506RA thermometer using a 36 gauge type T thermocouple. This type of thermocouple has the optimal accuracy at the temperatures that interest us (standard error limit tolerance is 1.5°C). I used a double ridgeless basket, dosed with 15-17 grams depending on the blend, and all coffees were between 3-5 days post-roast. Coffees were ground using a the Mazzer Mini grinder. I followed Schomer's NSEW distribution technique and used the MACAP auto-tamper to ensure consistent tamp pressure.
D'arte Firenze - I like this espresso extracted at 91°C. I set the temperature and waited five minutes for the machine to adjust, flushed and pulled my shot: The measured brew temperature 91.3°C; the shot was well rounded with pronounced chocolate, some smoke, and anise. Aftertaste was long and stayed sweet all the way.
Terroir Northern Italian - George Howell recommends 92-93°C for his blend. I looked at the light roast of those beans and thought: Fruit bomb. I pulled the shot and measured the brew temperature at 92.3°C. Ouch, time to call in the bomb squad! The flavors of lemon, apricot, papaya were way too sharp for my palate. I decided to work the shot later.
Ambrosia - My target extraction is 93°C. I repeated the above steps and extracted at a measured brew temperature of 92.7°C; nice bouquet of cherries, apricot, chocolate, with a gentle scent of wild flowers from the Daterra.
Redline - I like it at 94°C. Measured temperature was 94.2. Starting to see the pattern?
Vivace Dolce - David Schomer recommends 203.5°F for his blend, which translates to 95.2°C. Actual temperature was 94.9°C. Oh man, I nailed that one. Creamy and heavy body, fruity but low in acidity, and had some chocolate on top.
My own blend - Since it is mostly Indonesian and Indian, it pulls nicely at high temperatures: I dialed in 96°C and measured 95.5°C. In the cup it was heavy as advertised, mostly chocolate, but also some spice from the aged Indian.
Overall results: The Brewtus delivered the coffee attributes with high fidelity. They were all very satisfying, some flat out exceptional, and not one sink shot.
So let's try the same experiment on my Giotto Premium HX machine. I have had this machine for almost two years; I have done extensive temperature control experiments with it and consider myself an experienced HX user. In addition to the flush routine I developed through my own experimentation based on the fabulous write-up How I Stopped Worrying and Learned to Love HXs, I also tried the flush routine Chris Tacy outlined in his Pro's Perspective series on Home-Barista.com. Using his refinements of the "water dance" method, he was able to obtain accurately and consistently a much larger range of the temperature scale than is my experience. I found that what apparently worked wonderfully in his experimentation does not work well for my Giotto. I suspect that the problem lies in two areas. First, it is hard to determine the point to start the count down when the hissing stops because of the noise from the Giotto's vibration pump (this is less problematic for machines having much quieter rotary pumps). Second, an even countdown from the end of the water dance does not correlate to an even drop in temperature. It speeds up towards the end and also slightly changes according to how long the machine was idle. With the Giotto, I easily and consistently obtained 94°C and 95°C. However, hitting 91, 92, 93 and 96°C took a few tries, and the in-cup result was correspondingly inconsistent. Obtaining 91°C required a significant flush and even then it was off by 1°C. A brew temperature of 92°C was a hit or miss, and 96 was either 97 or 95 but never quite 96°C.
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Faema E61 Legend
thermosyphon flow restrictor |
As a side note to the topic of HX temperature control, I spent three days on the trade show floor during the SCAA 2004 annual convention in Seattle. There were hundreds of vendors there and almost every commercial machine manufacturer in the world. When I asked "how do you set brew temperature on a HX machine?", they all pointed to the boiler pressurestat. Those that had a flow valve on the thermosyphon loop also pointed to it as a means of further refining the group's temperature (similar to the one shown on the left from a Faema E61 Legend).
Reaching both consistency and accuracy in brew temperature with an HX machine like the Giotto requires more barista skills because brew temperature is only indirectly dictated by its boiler pressure. Fine tuning the final temperature requires the barista to master the flushing routine which clears out overheated water from the HX and allows the boiler pressure setting to do its intended job. The boiler pressure setting allows the barista to obtain the desired temperature from a possible range by adjusting the flush quantities, but only to a few degrees. Outside a certain range, getting consistent and accurate brew temperature from a machine like the Giotto requires me to change the boiler pressure, which is not practical on a frequent basis. I could change it of course, but it requires opening up the machine, and the adjustment represents a narrow range of temperatures, not a specific one. Simply stated, constantly tweaking an HX's pressurestat is neither refined and nor as accurate compared to Brewtus' electronically controlled brew temperature.
Now let's get back to Terroir Northern Italian Blend. What do you do with a fruit bomb? There are several variables you may adjust to defuse it: dosage and extraction time, temperature, and pump pressure.
Of these variables, I chose to focus on temperature to see if I could tone down the sharp notes. So I raised temperature to 93°C, pulled the shot, and ran for cover. Still too sharp! I tried increasing the temperature to 94°C and noted a marked difference in the cup. Sharp notes toned down, and I'm getting a little more nut in the cup and some chocolate. One more degree to 95°C you think? Yes, we have a winner! The cup is still fruity, but not so sharp on the palate. More understated, and the chocolate is more pronounced. I know that 96°C is going to be too high for this blend as Brazilians get ashy at high temps, but as an experiment, let's take it there: Yep, as expected, it's like drinking coffee from an ashtray.
When testing a machine I look to see how well it executes the specific coffee attributes. My evaluation parameters are the following:
Body and texture are different criteria: Body relates to the detectable solids in the brew which give it weight in the mouth. Texture refers to the type of solids. I prefer the sensation of heavy cream coating my palate. Clarity relates to the relationship between flavors: are all the flavors infused into one single "muddy" flavor, or do they still retain their identity, and can be clearly singled out. Total Impact is an instinctive total taste evaluation of the cup. Without dissecting it, how do I like it? Versatility relates to the machine's ability to work equally well with a variety of coffees and blends which require different brew temperatures.
In my shot evaluation, I used six different blends (see above) and one single estate coffee, Daterra Reserve 2004. I pulled each shot on the Expobar Brewtus and on the ECM Giotto Premium. I repeated the test five times for each coffee to test consistency in the cup. To ensure consistency between the machines in the shot preparation, I used the same baskets, same grinder setting for each coffee, same brew pressure, and I tamped all shots using the MACAP auto-tamper.
Once I determined the optimal dosage and temperature for each blend, Brewtus consistently delivered very good to excellent shots, with a few exceptional shots. Not even one sink shot. Very nice body and often creamy texture, and when the blend had it—complexity.
The Brewtus outperformed the Giotto on all categories. However, it is important to point out that the Brewtus clear advantage stems from one thing: its superior temperature control. As the Giotto struggled to deliver brew temperatures outside its comfort zone, the result in the cup became evident: mediocre to sink shots in 30% of the cases. The key to excellent espresso with the Giotto is choosing blends that work well within the comfort zone of its pressurestat (e.g., 93-94°C for most a typical pressurestat setting of 1.1 bar). For such blends, the espresso was equivalent on both machines. In one test I intentionally chose a temperature tolerant blend, the popular Black Cat blend by Intelligentsia Coffee Roasters. In this case, Brewtus and the Giotto performed equally well. The Brewtus advantage becomes evident for those who frequently change blends having widely varying temperature requirements.
A dual boiler machine must steam well in order to earn its reputation. Steam power is driven by a combination of boiler size, boiler pressure, power of the heating element and steam wand and tip design. The Brewtus' 1.7 liter steam boiler pressure is set to cycle between 1.1-1.25 bars. I would have liked to see it set at higher pressure setting, say 1.4 bars, and a more powerful heat element for quicker recovery. Brewtus' steaming power is slightly weaker than the Giotto, which enjoys a bigger boiler and a stronger heat element, but is more than adequate for my needs.
The stock tip is a single-hole tip, though WholeLatteLove will supply a two-hole tip to those who request it. The stock tip is ideal for novice users. This tip increases steaming time and thus allows an inexperienced user better control over the process. However, a more experienced user will want to ditch the single-hole tip for the two-hole version. By doing so, you can cut the steaming time in half, and more importantly, I found it produces better quality of velvety super smooth sweet milk. I also tested the Gold Pro 2 from 1st-line and found it to be a step between the single-hole stock tip and the WholeLatteLove two-hole tip. The holes on the Gold Pro 2 are smaller and you will not notice a sharp decline in steam boiler pressure compared with the WholeLatteLove two-hole tip. It should be noted that using a 2 hole tip causes a sharper decline in steam boiler pressure than the single hole, and as such will increase boiler recovery time. A sharp decline will also have some affect on water temperature entering the brew boiler, and if you are steaming and pulling a shot at the same time, it will have a modest impact on brew temperature. The two-hole allows producing both a rolling end to end wave for frothing, or a whirlpool. With the single hole, a whirlpool is the only way to froth. I used the standard technique for steaming which is well-documented in The Milk Frothing Guide.
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8 ounces |
10 ounces |
12 ounces |
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Expobar Brewtus - one hole (stock) |
84 |
87 |
104 |
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Expobar Brewtus - two hole (optional) |
29 |
40 |
46 |
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Giotto Premium |
28 |
38 |
43 |
Seconds required to heat water from 40 to 160 degrees Fahrenheit (boiler pressure of 1.2 bar)
I did all my steaming using a 12 ounce pitcher, as I have found it to be the most suitable size for the steam power of this machine. The 12 ounce pitcher is a perfect size for cappuccinos and macchiatos. I do not drink lattes, but tested steaming for 12-16 ounces latte on a larger pitcher. The milk texture for a latte was just as good as with the 12 ounce pitcher.
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