Single Group Slayer Review

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shadowfax
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Postby shadowfax » Aug 17, 2014, 10:41 pm

Introduction

Founded in 2007, Slayer Espresso produced its first espresso machine in 2009, a multi-group commercial machine hand-built in Seattle, WA. It featured a saturated group brew boiler, a dedicated tank for pre-heating brew water, and an innovative brew path with an array of needle valves and a 3-way valve actuated by a paddle to modulate shot flow and pressure. Slayer also focuses on espresso machine customizations, providing a variety of wood trim, color, and metal plating options and offering additional customizations by commission.

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The single group Slayer, shown with customize Xs, panel colors, and wood trim

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Slayer's custom needle valve assembly allows
the brew actuator to toggle between adjustable,
restricted flow and fixed high flow.
Slayer's group design has changed over the years, becoming hydraulically and mechanically simpler and requiring less upkeep. Its latest design, the "V3" group, has a paddle that acts as a large 3-way switch instead of actuating a 3-way valve; all the valves on the machine are now solenoid valves. A single needle valve (pictured to the right) controls the preinfusion (or "pre-brew" in Slayer's preferred terminology) flow rate.

After 6 years of producing multi-group commercial espresso machines, Slayer has brought its brewing technology into a home-friendly single group design. In addition to featuring a slightly miniaturized version of its commercial brew group and sharing a lot of hardware with the larger machines, the single group Slayer features a custom electronic controller with a touch-based user interface. This interface displays brew temperature, steam pressure, and brew time. It also allows control of brew temperature and pressure, steam pressure, an on-idle schedule, and many other features.

The Slayer has a size, feature set, and price to compete with the single group Synesso Hydra, Kees van der Westen's Speedster, and the La Marzocco GS/3.

Disclosure: I have purchased the Slayer used in this review, and as such this is a self-sponsored review. I have not received any special discounts from Slayer and do not have any financial stake in the company.
Nicholas Lundgaard

good beans = good times
Sponsored by Bodka Coffee - good beans = good times
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Postby shadowfax » Aug 23, 2014, 3:17 pm

As we have done with previous reviews, this one will be a series of blog posts that delve into various aspects of the Slayer's design, features, and performance, culminating in a final summary that is published as a brief review once complete.

I'd like to begin the review with a discussion of what it's like to purchase and receive a Slayer. From there, I will highlight some of the Slayer's unique and interesting features, its construction, and the initial experience of pulling shots with the machine.

Ordering, Shipping, and Setup

Ordering a single group Slayer is somewhat different than most machines: there's no "retail" price, and very few distributors. Priced between the Speedster and Synesso one-group Hydra, the machine is also shipped much like those machines—bolted by its feet onto a wooden pallet with a wood-framed crate covering it. Shipping alone is done by a freight carrier. This requires either a commercial receiving facility or a lift service for delivery, and generally adds a few hundred dollars to the price. The shipping crate weighs a whopping 160 lbs. and requires two people to safely lift.

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The Slayer is shipped in a large wooden crate

The machine itself weighs in at about 110 lbs. with the boilers filled. This is around 30-35 lbs. heavier than a GS/3, and as such it is more difficult and impractical to move alone (Slayer recommends against this). Its large feet are set with ~1" diameter rubber feet that practically glue it to whatever surface it rests on. This is excellent during actual use, but can be frustrating when setting up and moving the machine. Slayer recommends placing towels under its feet in order to adjust its position on the counter. This works very well. However, this would be a challenging machine for mobile catering. I've had a number of experiences catering with the GS/3 at Free Press Summer Fest in Houston, and it is not too heavy for one person to set up. The Slayer needs two people to move, and its plumbing requirements require extra equipment.

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The Slayer is packed with minimal padding, secured instead with bolts and straps.

With a footprint 16" wide by 18" deep, the machine is a little wider and shallower than a GS/3 (16"W x 21"D). Like the GS/3 and Speedster, the Slayer easily fits under the lowest of kitchen cabinets; its height is 13", but the steam and water levers bring the total height to about 15". It also comes in a 110V version that can operate on a 15A circuit, but does not contain or support use with a water reservoir. The machine needs positive inlet pressure for the pump and a drain or bucket for the drip tray. You can, however, set up the machine to draw from a five gallon bucket using a delivery pump like a Flojet. If you choose to set up the machine like this, note that it also needs an accumulator tank and a pressure regulator for consistent inlet pressure. The machine uses a Fluid-o-Tech gear pump that amplifies inlet pressure and will translate inlet to outlet pressure fluctuations. This is also true of most espresso machines that use rotary pumps, but the effect appears to be more significant with the gear pump.

After connecting the water supply, drainage, and electricity, the machine powers up and fills each boiler. First-time setup requires calibrating the pressure transducer that controls the steam boiler and bleeding the group to force out any trapped air. Both of these processes must be performed through the touch interface behind the cup tray. This interface acts as the display for boiler temperature, steam pressure, machine state, and shot timing. It also has an iPod-like touch interface for adjusting machine settings, performing automatic maintenance features, and programming the schedule for the machine. Slayer has posted a short video of the basic mechanics of the interface on their Facebook page, which gives a sense of what it's like to use. After calibration and group bleeding, the machine is ready to have the elements for each boiler enabled, which is also performed through the touch interface.
Nicholas Lundgaard

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Postby shadowfax » Sep 02, 2014, 10:10 am

Build and Layout

The single group Slayer, unlike it's larger brethren, is not built around a center spar suspended by X-shaped legs on either end. Instead, it is built on a half-inch thick aluminum base plate that the Xs are attached to by a pair of aluminum brackets.

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The Slayer's iconic Xs attach to the base by these three-quarter-inch aluminum brackets.

The side panels of the machine, also half-inch thick aluminum plates, attach to the Xs to complete the side walls. This base layout forms a rigid skeleton that does not rely on braces higher up to keep it rigid and aligned.

The two stainless steel boilers are bolted directly to the base plate of the machine. The heating elements are sheathed with inconel instead of copper, which Slayer says allows them to run dry much longer without deforming.

A moulded stainless steel sheet separates the main compartment of the machine, which houses the boilers, from the rear compartment, which houses the pump and electronics. This piece isolates the electronics and pump from much of the heat from the boilers. In turn, the rear compartment contains a separator between the pump and electronics to protect the electronics from any potential leak. The electronics are elevated to minimize the possibility of their exposure to water:

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The rear section of the machine houses the pump, 24V power supply (above, left), heating element relays (obscured by the power supply), and brain board (above, right).

Another interesting detail is that wires aren't bundled together into a single conduit that makes tracing them difficult to do without partially dismantling them. The wires for each component are bundled together with heat shielding and run directly to each component.

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The Slayer's wiring is very easy to isolate by component.

The Pump

As previously mentioned, the single group Slayer uses a Fluid-o-Tech gear pump. This pump is compact and efficient, and provides a flow rate that is better-suited to use for espresso than the rotary pump that is more typically seen with commercial and high-end espresso machines. Additionally, the pump pressure delivered declines as the flow rate increases (given a fixed pump speed), producing a slightly declining brew pressure during an extraction.

There are some drawbacks to the pump, however. It costs four to five times as much as a rotary pump, and it sounds a bit like a muffled dentist's drill. On my Slayer, the pump's high-frequency vibrations can sometimes cause intermittent buzzing inside the machine. I've found this can be resolved with a small amount of tinkering, however, and when functioning correctly the pump's hum is more noticeable than that of a rotary pump, but less grating than most vibratory pumps seen on consumer-grade espresso machines.

I'll return to the pump as it relates to extracting espresso in a future post.

The Drain System

The Slayer's drain system has a few unique features. A stainless steel drain box located inside the machine receives the drain lines for both boilers as well as the 3-way exhaust and overpressure valve lines. Each boiler can be drained by turning a 90° ball valve located on the lefthand side in the machine. This makes periodic steam boiler draining very convenient, something Slayer recommends to prevent mineral concentration creep from steaming.

Compared to drain boxes on most commercial espresso machines, the Slayer's is much deeper. It functions very effectively for bleeding the group (which purges water and trapped air out of the OPV) and for pulling shots and backflushing. I have yet to test it out for boiler draining. One potential problem I foresee with the placement and design of this box is that the opening on the top is small and somewhat difficult to reach; this means that cleaning it will probably require a special scrub brush and may be more troublesome than it is for machines where this box is located under the drip tray.

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The drain box is plumbed to both boiler drains for convenient boiler flushing.

Rather than being connected directly to the drain line, the Slayer's drain box feeds into the drip tray via a flexible rubber tube shown on left side of the image below. The drip tray itself is well-made and designed to effectively drain much larger volumes of water than a typical workflow would produce. Having said that, though, most of the tray is near-flat and not graded to fully drain. This means that a small amount of coffee residue remains in the tray.

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The large drip tray is designed to drain quickly, if not completely.

The drip tray is covered by one of the most effective and attractive grates of any machine I've ever used. The grate is made from a thick, perforated sheet of stainless steel that is rigid and guides even very large spills and flushes into the drain rather than over the edge onto the counter. The texture of the metal is slightly matte, contrasting with the polished trim and minimizing the appearances of scratches imparted by placing cups on the grate.

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The Slayer's drip tray grate is attractive, effective, and rugged.

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The drain line is angled nicely to facilitate thorough clearing.

The Steam Wand

Slayer integrated the steam wand assembly from their commercial machines directly into the single group. As I understand it, the only difference is the length of the handle for the steam levers, which are shorter. I believe this change is primarily so they look proportional on the machine. The steam wand is actuated by a lever that rotates a bearing mounted disc. As you pull the lever forward, an angled face on the disc depresses a pin that gradually opens a valve. The disc is attached to the machine on a bearing and can be tensioned to the desired level of resistance using a locknut. It has a very smooth travel, and the wood handle gives it a very premium feel.

The steam wand itself is a classic "burn me" wand. Its length is such that it can be easily purged into the drip tray, although this makes a mess if you open the valve fully. One feature of the wand that is very convenient is a cutout above the threads of the steam arm that seats an o-ring. This o-ring seals the steam tip, eliminating the need to seal it using teflon tape or tightening it on with a wrench. It seals perfectly and only needs to be hand-tightened.

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The Slayer steam arm features an o-ring that eliminates steam tip sealing problems.

In addition to an easy-to-remove steam tip, Slayer offers a range of tips for their machine, numbered 0-5. The numbers correspond to hole sizing: the #0 tip has four 1.0 mm holes, and each subsequent tip increments the hole size by 0.1 mm. The stock tip is the #2 (1.2 mm). This makes it easy to size the steam tip to your skill level and milk volume. I purchased the #0 and #1 tips in addition to the #2 tip that came on the machine.

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Slayer sells a range of four-hole steam tips for their machines, ranging from hole sizes of 1.0 to 1.5 mm.

The steam boiler has a capacity of 3.3 liters and features a pressure transducer for controlling the heating element. This means that you can set the pressure in bars through the electronic interface. It is sized to provide power that is comparable a multi-group commercial machine, which can be intimidating for beginners. However, using a lower pressure setting and the #0 tip slows the steaming down nicely for those who need extra time while getting the hang of texturing.

I'm not sure how much of a reference point this is, but before I received the Slayer, I had been using an espresso-only machine. As a result, I'd prepared only a handful of milk drinks over the past 18 months. This was the result of my first attempt on the machine:

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My first cappuccino on the Slayer.

In practice, the machine steams much like a GS/3 with a "burn-me" steam wand installed. The range of motion, power, and capacity are nearly identical. The Slayer's steam lever is slightly easier to control than GS/3's. However, its placement makes it more awkward to use for left-handed steamers like myself. To give a sense of what steaming is like, I made a short video of steaming and preparing a 5 oz. hot chocolate. I have the boiler set to 1.4 bars and I am using the #1 tip (1.1 mm hole size). This yields a 10 second steaming time, which could be shortened further with a higher boiler pressure and a larger tip. I will record more detailed timings in a future installment.


Preparing a hot chocolate/steamer with the Slayer.

The Water Tap

The Slayer's water tap is an unusual standout among its competitors: it does not feature any kind of cold-water mixing valve to tame the sputtering, super-heated water that flows from the bottom of the steam boiler. This has the obvious disadvantage of being noisy and messy. If there is any advantage to it, it is that this omission saves a good deal of space and complexity inside the machine. This is very much in line with Slayer's minimalist design, but at a cost to usability (which the machine otherwise scores very high on). For me, it is a mild annoyance that deters me from using the water tap for anything other than periodic water purges to help keep the mineral level in the boiler low. I've created a video that demonstrates a five ounce purge into a cappuccino cup:


The water tap is a sputtering dragon.
Nicholas Lundgaard

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Postby shadowfax » Nov 10, 2014, 2:33 am

'Pre-brew'

Water debit. Flow rate. Gicleur. Jet. Preinfusion. Progressive preinfusion. Pre-brew.

There's more than one way to skin a cat, as they say. Espresso is supposed to be pulled at around 9 bars to achieve its distinctive texture, but of course that is far from the whole story. How you get to 9 bars, it seems, is pretty important.

Slayer's method is unique: when the brew actuator is in the middle position (pre-brew mode), water pressurized to 9 bars flows through a needle valve that allows you to set the water debit (flow rate) as low as you want. While most espresso machines have a water debit of 8 or more grams per second, the Slayer's water debit in pre-brew mode is generally set to 1-2 grams per second. With that setting, there may be 15 seconds or more between exposing the coffee puck to water and applying pressure to it—and the rate of the pressure ramp after that is more gradual compared to a typical espresso machine's. However, when the Slayer's brew actuator is in the left position (brew mode), the water passes instead through an 0.7 mm flow restrictor. In this mode, the water debit is a more familiar 9 grams per second.

Compare this pre-brew mode to an old La Marzocco Linea or an Elektra A3/T1. These machines have either no flow restriction or a very wide flow restrictor. They apply full pressure to the coffee puck in about 2 seconds. This tends to result in a machine that is either unforgiving, picky about dose, or both. These machines are quite capable of pulling delicious espresso, but they can be frustrating to use or limited in the style of coffee that they can excel at extracting.

That said, machines with a 'gentler' rise to full pressure hardly a new phenomenon. Home espresso enthusiasts have long lauded the famous Faema E61 brew group. It features a preinfusion chamber, a pocket of air downstream of the flow restrictor that increases the time required for the incompressible water to fill the space above the espresso puck, delaying smoothing the pressure ramp considerably and resulting in a more forgiving espresso machine. This design pattern has been used in various incarnations in many well-known espresso machines, such as the La Spaziale S1, the Nuova Simonelli Aurelia, and the Kees van der Westen Speedster. Indeed, a "sipper" lever espresso machine that draws water from the steam boiler to fill the lever piston features a similar design, and that design precedes pump espresso machines entirely.

Another common design is to use a narrow flow restrictor. The smallest in common use is the 0.6 mm flow restrictor found in modern La Marzoccos and Synessos, among others. Like a preinfusion chamber, this flow restriction delays the rise to full pressure and makes for a more forgiving espresso machine.

Lastly, there is line pressure. Many espresso machines (famously, paddle group La Marzoccos and the Synesso Cyncra) feature the ability to apply water at line pressure (generally 2-4 bar) to the coffee puck prior to engaging the pump for full pressure.

Various combinations of these designs exist and have been in wide use for many years. And it is very likely that the variations in the pressure ramp and flow rates that a machine provides accounts for a significant part of what differentiates one machine's 'personality' from that of another. In that light, "preinfusion" is a rather loaded word that requires further explanation to understand in detail. However, all of these designs have one thing in common: they come to some pressure (more than 1 bar), if not full pressure, within 6-8 seconds. To differentiate their design, Slayer calls their preinfusion phase "pre-brew." In the interest of clarity and succinctness, I will use that term when referring to "Slayer style" preinfusion in this review.

In my experience, using pre-brew goes beyond enhancing the "forgiveness factor": this kind of preinfusion requires grinding so much finer, all other things being equal, that the resulting shot is very different in character. This concept is discussed at length in a previous discussion, "Pressure profiling, flow profiling, and a new rule of thirds."

Pulling Shots

To illustrate how pre-brew affects the shot flow, I have prepared a series of videos. The Slayer has a brew pressure gauge on the front panel that measures pressure downstream of any flow restriction, meaning that it reads the pressure of the water on the puck during a shot. It also has an angled "shot mirror" that allows you to see how your shot is flowing through a naked portafilter without the need to bend down and look up from below. This makes capturing pressure and shot flow at the same time very convenient.

In the videos below, each shot uses a 19 gram dose, and the shot is stopped at 30 grams, for a 63 percent brew ratio. The first demonstrates a "Slayer style" shot with a long pre-brew phase (25 seconds at 1.5 grams per second flow rate) and a typical total brew time of around a minute. It also shows re-entering pre-brew phase at the end of the extraction to restrict flow, tailing pressure and flow rate at the end of the shot.


Slayer style shot—long pre-brew.

For this particular coffee, a light roast of a bright, clean washed Costa Rican, a long pre-brew phase works nicely. The sweetness is ample, balancing out the tart citrus with sweet middle tones.

The second video demonstrates using a "traditional" approach simulated by performing a short 5 second pre-brew phase, using the same grind and dose as before. The result is a choker whose total time is only a little longer than the previous shot's, but whose time at full pressure is considerably longer. This tastes as you would imagine—acrid, cooked, and over-extracted.


"Traditional" brew profile, same fine grind.

Note that this isn't the only way to simulate such a "pressure profile." One could also loosen the needle valve to give a larger water debit (say, 6 grams per second); I have not investigated this in any detail, however.

Finally, here is a demonstration of the same coffee and dose with a much coarser grind (4 notches on my K10 Pro Barista).


"Traditional" brew profile, coarser grind.

With the coarser grind, the shot flows normally and completes in about 27 seconds. This particular coffee did not work as well in this format, tasting rather sour and under-developed. In this case, if pre-brew weren't available, I would dial this shot in by lowering the dose to allow tightening the grind, and probably also use a lower the brew ratio. Note, however, that these changes would almost certainly entail sacrificing shot body and concentration to achieve taste balance.

This serves to illustrate what the Slayer is best at: making it easy to get an well-balanced, full-bodied espresso shot from a dense, light-roasted, high-grown washed coffee.

As another example of this, last month fellow forum member Mike Ivanitsky challenged me to try a ridiculous coffee that normally wouldn't be suitable for espresso and brew it on the Slayer. I selected George Howell's La Esmeralda Mario San Jose, a washed gesha grown at around 1500 meters. I guessed the grind based on a visual assessment of the roast degree, selected my usual ~18g dose for my basket of choice (VST 18 gram basket), and pulled a shot with about 20 seconds in pre-brew, shooting for a brew ratio of around 60-65%. The first shot was good, but a little too tart. I tightened the grind slightly, raised the temperature setting, and repeated. The second shot was amazing. The aroma was full of fragrant orange floral tones, and the shot was candied orange with tons of caramel flavor.

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La Esmeralda Mario San Jose espresso—a shot of fragrant orange flower honey.

I also reviewed the Chicago Trio that Jim Schulman graciously sent us on the Slayer. They serve as good examples of when Slayer's pre-brew feature works very well, and when it's preferable to use a coarser grind and a more abbreviated pre-brew time (i.e., a more typical pressure ramp).

  • C1 was a very nutty, creamy, lightly acidic northern Italian style espresso. While I was able to use long pre-brews and produce good shots, it didn't truly shine until I cut my pre-brew short and used a faster pressure ramp and coarser grind.
  • C2 was another espresso blend featuring a healthy dose of pulped natural Brazil. It practically demanded a coarse grind; all the fine-ground, extended pre-brew shots came out acrid and bitter.
  • C3 was easily my favorite of the Chicago trio. An SO from El Salvador, it was clean, bright, and worked extremely well with a long pre-brew phase, which made its Sweet Tart acidity pop. It also was easy to tame the acidity and bring the caramels to the forefront by lowering the dose and temperature together.
Nicholas Lundgaard

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Postby shadowfax » May 09, 2015, 9:42 am

Temperature Stability & Reproducibility

Since around February/March of this year, I have been evaluating an update to the Slayer's firmware. I went through a few rounds of feedback with them, and at the end of March, I received the final update (1.7.1a). I have confirmed that this update has fixed all the stability issues that I and others have noted (see this thread started by forum member Bob_M for details).

This update is being provided by Slayer to all customers, and I believe it has been shipping on new machines at least since the end of March as well. The update process involves moving a jumper pin on the board, plugging in the dongle with the firmware update on it, and pressing a button on that device to copy the update onto the device. It appears that this update preserves all settings on the device, so early users will probably want to update their PID settings to P=200, I=2, D=0 per the factory recommendation.

This firmware update appears at first glance to be noticeably more stable than the early (1.6.x) firmwares, and according to Slayer, it also includes some additional optimizations beyond PID, such as applying the heat for a certain amount of time when the group is in use.

With that in mind, I turned my attention to benchmarking temperature stability. To that end, I developed a slightly modified form of the WBC Procedure for the Measurement of Brewing Water Temperature in Espresso Coffee Machines. I will preface my results with an explanation of the protocol and its minor deviations from the original (update: further discussion of the method can be found here).

The Protocol

I wanted to preserve the core of the shot-pulling procedure. Below is an explanation of the workflow; It is unchanged, except inasmuch as the timings are a little more detailed and expressed in a way that I found easy to implement.

Code: Select all

Time   Duration  Action
0:00   0:15      Start Datalogging
0:15   0:10      Remove portafilter (shot prep)
0:25   0:02      Flush 2 sec.
0:27   0:03      Insert portafilter
0:30   0:25      Pull shot 1
0:55   0:01      Remove portafilter (flush)
0:56   0:02      Flush 2 sec.
0:58   0:07      Insert portafilter at end of 7 seconds
1:05   x:xx      Idle Interval
y:yy   0:10      Remove portafilter (shot prep)
z:zz   . . .     [ repeat ]

This retains the structure of the WBC preparation spec almost exactly:

  • Portafilter out for 15s prior to the shot, with a 2s flush right before (simulated shot preparation)
  • 25s shot time rather than a volumetric shot simulation. This was for simplicity, and because 25s shots fall in the water output range specified by the original protocol
  • Portafilter out for ~10s immediately after the shot with a 2s "clearing flush" right after removing it.
The changes I made were my choice of shot intervals. Rather than 14, I opted for only 10 shot simulations, using the following intervals between each:

  1. 10:00+ ("idle time" before pulling the first shot)
  2. 5:00
  3. 2:00
  4. 2:00
  5. 1:00
  6. 1:00
  7. 1:00
  8. 0:30
  9. 0:30
  10. 0:30
In addition to reducing the total number of shots, I omitted the 10s interval series at the end, instead using a minimum interval of 30s. I opted to use 3 each of the 1:00 and 0:30 intervals at the end. The point of this is to make the test reflective of a home-user's pace.

A copy of this protocol in Excel spreadsheet format is available here.

The Results

I set my Slayer to 200°F for the testing. Note that this setting is based on my own offset adjustment, so the raw result numbers' offset from 200°F is of litte importance; I may need to re-adjust it later. The point of the testing, of course, is the consistency of the results.

Here are the average temperatures for each of the 10 shots (idle time in parentheses):

  1. 198.7 (10:00+)
  2. 198.6 (5:00)
  3. 198.0 (2:00)
  4. 198.5 (2:00)
  5. 198.3 (1:00)
  6. 198.1 (1:00)
  7. 198.5 (1:00)
  8. 198.8 (0:30)
  9. 199.8 (0:30)
  10. 199.1 (0:30)
The data indicate very good reproducibility (often referred to as inter-shot stability). Note that the temperature rose noticeably when the idle time was reduced to 30s. I included that short interval series as a matter of interest, but I consider it a very unrealistic pace for anyone but an experienced barista (or pair of baristas) catering an event. If you exclude that data, the consistency is superb.

Here are the shots plotted together, with a few isolations to demonstrate the effect of omitting the 30 second intervals:

Image

Image

Image

One thing that I've noticed with the Slayer more so than the GS/3 is that it seems to have a pretty steadily increasing temperature profile throughout the shot. In other words, the slope of the "top" of the hockey stick is more pronounced than I see with a GS/3. This isn't a negative observation by any means—as I said before, reproducibility is the primary concern, and it scores well there.

I calculated the temperature reproducibility and stability, per the WBC protocol specification. I've included calculations for all shots (1-10), omitting the first few shots (3-10), and omitting the 0:30s intervals (1-7).

Code: Select all

6.3 Brew Temperature Reproducibility (2 * Standard Deviation)               
Shot
Range    Value      2X
 1-10     0.54    1.07
 3-10     0.61    1.22
 1-7      0.26    0.52

Code: Select all

6.4 Espresso Machine Temperature Stability (Average of Averages)
Shot
Range   Value
1-10    198.6
3-10    198.6
1-7     198.4

The Raw Data

I've compiled all the data I collected (using the handy Artisan software) into a spreadsheet, available here. This spreadsheet includes a sheet that contains the protocol used, as well as all the computations and graphs used above (please feel free to check my work!).

A quick note on the data: As you will see, I didn't always hit the shot start to the second of the protocol. I did my best to compensate for those errors by shifting the shot start times in the series (for calculations) by a second or two. Per the WBC spec, I did not include the first 3s of shot temperature data in the average temperature calculations.
Nicholas Lundgaard