Slayer Steam Espresso Machine

(Conor McCann) #13

I tried both milks from traditional wet and the slayer dry steam and again like others found it was definitely sweeter, I didn’t get a chance to taste it in coffee.

The milk they were using is what I use in the shop everyday, and I was really surprised by how sweet it was tbh, however I rarely if ever just taste the steamed milk on its own.

I wasn’t however mind blown by it. I was more mind blown by the fact that it was completely clear coming out of the steam wand haha

I was intrigued by the texture, it seemed to be a lot dryer then usual, texture wise. The exhibitor was quite busy when I was there do I completely missed the science explanation so I’m sorry if that’s common sense obvious ( wet foam = wetter, vice versa) this led me to thinking of day to day use. I think the milk, by looking at it ( in my opinion) looked a little bit tricky to pour nice latte art. I know it’s not the most important thing but I still believe quality presentation is very important… Does anybody know if my assumption is correct, is it harder to pour nice latte art ?

The machine did look beatiful … Nowhere near as sexy as the new spirit by Kees van westen. It is gorgeous and unlike the slayer I got to play around with it at the world of coffee and it was a great machine to use… An absolute pleasure ( added points for looking like a spaceship) it may just win my heart over from la marzocco.

(Levi Andersen) #14

Latte art… hmmmmm great question… They said because of the lack of water in the milk it has an ability to hold the shape/image longer. But - I wonder about the pouring itself, what part does the water play if any at all?

I tried both, 2 times. The new way was more similar to milk with a splash of condensed milk in it. The ‘old way’ had an odd old milk smell to it. So weird, because I love lattes. Very cool to see, I posted a little video on my Instagram if that helps anyone ( - cheers!

(Conor McCann) #15

It was just a thought, I know it’s not the most important thing but it’s something to keep in mind.

The point about the milk holding texture longer is interesting, it might make for a more consistent cup. Get rid of my need to drink milky coffees quickly to maintain the nice creaminess of freshly steamed milk.

I agree with you comment on condensed milk. I can see the similarities.

(Jackson Cate) #16

Curious, did it seem to take longer, shorter, or about the same time to steam the milk? vs traditional wetter steam that is @Levi_Andersen

(Conor McCann) #17

It actually seemed to take longer, there was a person steaming both sides and they started around the same time and the wet steam was ready first, quite a few seconds before actually … But I’m not sure how much milk was in each pitcher tbh

It definitely seemed quite long to steam a small 12oz pitcher with the dry steam which I found odd.

(Dillon Smith) #18

If drier steam means a longer time to reach the target temperature then better texture and flavor would make sense to me.

MattPerger mentioned in a post about milk that bubbles separate flavor from one’s tongue. Therefore, the smallest bubbles possible (the finest microfoam) is desirable. I achieve this on bar by using cold milk, a cold pitcher, aerating as quickly and uniformly as possible, and submerging the tip as little as possible to stop aeration and continue rotation.

Sometimes I show trainees the difference between the milk they steam this way with milk steamed very quickly- submerged as deep as possible after aeration. The latte art falls apart after a short time with this milk compared to the milk that has taken longer to steam.

If the dry air from this steam wand buys the barista another couple seconds of rotation then I would expect the texture to be better and produce more resilient latte art than a conventional wand.

(Levi Andersen) #19

I didn’t notice - but Nelson the Slayer barista said it did take a small amount longer.

(Scott Burlington) #20

I have a more general question: it says “classic 9 bar extraction” on the site.

Does it not have the Slayer preinfusion/pressure control as the regular machine?

(Komette) #21

No preinfusion on this one.

(Sarah Dooley) #22

Hey there Matt! We’re tickled that you are just as excited about Steam and the addition of volumetrics as we are! p.s. we love this thread.

(Sarah Dooley) #23

Good day to all of you and thank you for engaging so openly with the launch of Slayer Steam. I’m Sarah Dooley and I work primarily in Marketing at Slayer, although R&D is where I’ve spent the last 6 months learning and testing.

Let me begin by saying that we recognize there are a lot of questions. Our research has produced solid answers, but we will conduct further tests if we come up short in any conversation. You all deserve the truth.

I want to take this one topic at a time, starting with dry steam / dilution.

The core technology inside of Slayer Steam is a compact super-heater, which we call the Vaporizer. As steam leaves the boiler, it passes through the Vaporizer and is flash-heated at high temperatures to remove water, resulting in a dry vapor. Our steam tank is usually set to around 250º F; the Vaporizer is much hotter, producing steam that registers at 360º F. (That’s the output temperature, not the element setting.) Compare this with a conventional system, which produces steam that registers around 212º F at the wand.

The result is a drier steam that is nearly invisible. Counter-intuitively, perhaps, drier steam results in slower heating because the liquid water in conventional systems actually helps to transfer heat. When compared to Slayer Espresso, Slayer Steam takes 3-4 seconds longer to bring 150 mL of whole milk to 130º F.

So, this dry steam uses less liquid to heat milk. This brings us to the topic of dilution. Simply put, we don’t “water down” milk as much as most machines do. Conventional systems add an average mass of 10% liquid water back to the milk. Slayer Steam averages 6.5%. Does a difference of 3.5% really matter? We think so.

SCAA and SCAE Gold Cup Brewing Standards tell us there is a preferred flavor experience window that is just around 19-22% extraction. That’s a window of 4%. Swing that pendulum just 3.5% under or over and you can write yourself out of winning the brewers cup or, for what it’s worth, hitting the masses where their palates want flavor to be.

You can taste the difference with a simple test: heat two airtight bags of milk via sous vide, then dilute one with 3.5% of its mass in water. Similarly, anyone who enjoys scotch (like me) will note that adding just a few drops of water to a very complex scotch will change the experience completely.

We will be the first to say that we did not make all of these conclusions on our own. Over the last few months, we employed three outstanding food and coffee professionals to make sure that we weren’t “drinking our own Kool-Aid”. We believe that these are real changes, which will make a real difference to our guests cup experience.

Thanks for participating in this with us; more info is coming soon. For now, let’s keep talking about dry steam and dilution!

(Troy) #24

My perspective on this is a little different (apologies in advance for the brain dump).

It’s true, there is a large increase in enthalpy associated with the “change of phase” from liquid to vapour (which is because the molecules that escape the liquid are those with the greatest kinetic energy). However, I’m not entirely sure it is valid (or relevant) to say the steam changes phase back to liquid and “realeases” that energy when it is added to the milk.

I find it easier to think in terms of the specific enthalpy (the enthalpy per unit mass). Consider the hot steam and cold milk separately - each has it’s own specific enthalpy (related to it’s temperature). When the steam is mixed into the milk, the temperature of the resulting mixture is a function of the specific enthalpy of the mixture - which is approximately equal to the mass weighted average of the specific enthalpies of the milk and steam. What, if anything, changes phase (and at what temperature this might occur) is essentially irrelevant.

A few thoughts:

  1. Saying a superheater removes water is potentially misleading. Dry steam (whether superheated or saturated) is 100% water, it’s just that there is no liquid phase present. It’s more than likely all of the water entering the superheater ends up in your milk.

  2. Superheated steam is dry steam which has been heated to greater than the boiling point (at a given pressure). It has a greater specific enthalpy than either wet or dry saturated steam which is why you need less of it (by mass) to heat your milk.

  3. As other have mentioned above, I’m also not entirely convinced about caramelisation occurring (I would be interested to know if this is just a theory, or if it has been verified analytically).

Regarding the reports that heating milk takes longer with the superheater on:

  1. There is no reason I can think of that superheated steam would transfer heat more slowly to the milk than saturated steam, in the case of direct steam injection. I’m quite sure conduction is not a factor.

  2. One plausible explanation is the superheated steam having a lower density than saturated steam (wet or dry) at the same pressure:

  • Assuming the same steam tip, I would expect the volumetric flowrate to be close to that with saturated steam and the mass flowrate would therefore be lower.

  • My quick and dirty back of the envelope calc (which assumes the equal volumetric flowrate) suggested it would take around 10% longer to heat milk to the same temperature (comparing superheated steam at 180C to wet 90% steam at 125C).

  1. The slower heating could also perhaps be partly responsible for the reported improvements in milk texture (in addition to the reduction in dilution):
  • Bubbles are broken up by shear stress, which is influenced steam velocity (and thus volumetric flowrate).
  • Exposure to approximately the same level of shear stress over a longer period, might perhaps result in smaller bubbles.

(Andrew Baker) #25

Hi @Bayard

I believe it does have pre-infusion but it is of the mechanical variety not through variable flow control. The Slayer Espresso is still the machine for profiling espresso. The Slayer Steam combines the traditional consistency of pre-infusion, flat pressure & volumetric dosing with epic milk from the new ‘vaporizer’ super heater. I think it is aimed for specialty coffee houses with high milk volume.

Im guessing you can still adjust the flat pressure at the pump - @sarahdooley, is this all correct?

(Sarah Dooley) #26

Hey there @AndrewB and @Bayard, I’m happy to interject a few facts. You are correct Andrew, our newest machine is volumetric however there is not a programmable pre-infusion feature and you can adjust the pressure very simply at the pump.

For added clarity the term pressure profiling was used, Slayer Espresso has a two phase water delivery system. In phase one an adjustable needle valve delivers water pre-pump, to the coffee bed. This is the bloom phase of extraction to saturate the puck thoroughly before pressure is added to the system. Much like what we all do when brewing pour-over or setting a pre-wet phase on our brewers. Phase two engages the pump at the pressure you determine is right for the coffee.

Does that add clarity?

(Matthew Perger) #27

I believe you’re underestimating the latent heat of condensation. It’s more than 50% of the thermal transfer. Without it, you’d need steam at 680C, which this machine certainly doesn’t do.

(Troy) #28

I think the idea that “condensation” of the bulk vapour occurs at some point, and that this point is when most of the heat transfer occurs, is somewhat inconsistent with the physical reality.

If we were indirectly heating the milk (say, with heat transferred through the walls of a heat exchanger tube) then you’d be (mostly) right. But that isn’t what is happening in our case. We are adding the hot steam directly to the milk and the mode of heat transfer is entirely different (because it also involves mass transfer).

My way of thinking about it is as follows (it’s somewhat oversimplified, but useful enough):

  • Temperature can be thought of as a measure of the average kinetic energy of the molecules in a fluid (not all molecules have the same kinetic energy).
  • The water molecules in the steam are moving much much faster than those in the milk.
  • When steam is injected into to the milk, water molecules from the steam will cross the liquid / vapour interface (which strictly speaking, is condensation).
  • Each molecule which crosses the interface:
    a. depletes the mass of the steam vapour
    b. increases the mass of the milk
    c. increases the average kinetic energy of the milk (increasing the temperature)
    d. then interacts with molecules in the milk, transferring some of it’s kinetic energy to them (changing the distribution, but not the average and thus not the temperature)

My assumption is that this happens very rapidly and that condensation as it is commonly thought of (bulk steam condensing into liquid droplets) is not required to transfer heat to the milk.

That said, I could be completely wrong; I’m certainly no expert in thermodynamics or kinetic theory.

It is interesting to note that the vapour phase exists even below the boiling point and that looking at steam table data it appears the specific enthalpy of the vapour phase does not change markedly when you cross the boiling point curve (there is a general trend increasing with temperature).

Boiling is only relevant because there is a significant increase in the amount of vapour (relative to liquid). You can calculate the amount of steam mass required to heat a given mass of water, by accounting for the difference in specific enthalpy between the initial and final condition. The result should be numerically equivalent to using the specific heat capacity (i.e. change in specific enthalpy per unit temperature ) and the latent heat of condensation (i.e. change in specific enthalpy per unit mass condensed).

It may also interest you to know it is theoretically possible to reach the superheated condition without going through the boiling phase change at all - it does require pressurising the water to greater than it’s critical pressure (~ 221 bara from memory) prior to heating though. :sweat_smile:

(Matthew Perger) #29

Have you read this? The latent heat of condensation is literally doing half the work.

(nicolas) #30

@MattPerger @DIYCoffeeGuy where can someone learn all of this science? can it simply be googled or does it have to be studied somewhat academically? this chat is enthralling but I can’t say I understand the majority of the terminology

(Matthew Perger) #31

Hey Nico!

It’s all pretty simple. Definitely not degree-level. I only did high school chemistry, physics and engineering.

Best bet is to look at explainer videos for specific heat, latent heat of condensation, and thermal equilibrium.


(Chris Bodnar) #32

What I find most curious is that Slayer has decided to split their machine offerings in such a specific way.

High volume cafe that relies mostly on ‘press a button and go’ :: get the Steam.

But where does this leave the Slayer Espresso? Is it now considered a machine mostly specialized in extracting different flavors etc from coffee?

Is one or the other better for a cafe with a serious coffee program? Or are they just ‘different’?

Another thought to throw out to you fine folks - when it comes down to it, which (or what) makes the better milk-based drink? An espresso with all of the potential nuances brought out in a variety of different way (a la Slayer Espresso and its water debit) or is the texture/taste of the milk more important? Sadly the machines are geared/marketed towards preferring one over the other … Is a combination the best?

I realize I’m asking theoretically, and there is probably no right or wrong answer, but I’m hoping it creates discussion around those milk-based drinks (which consistently seem to take a back seat, even tho I’m sure the vast majority of cafes serve far more of these compared to straight espresso).