An Interview with Greg Scace
Greg Scace has been involved in the Third Wave Coffee Movement since the early 2000’s. Based in Washington, DC, U.S.A., he is best known as the creator of the Scace Thermofilter device, the cutting edge tool for monitoring temperature and pressure in espresso machines. Greg earned his BS in Mechanical Engineering at the University of Maryland, and spent 33 years as a research engineer, developing new ways of measuring humidity, temperature, and pressure at the National Institute of Standards and Technology.
Les Kuan is a Canadian Barista Academy Co-Founder, Head of Curriculum and Dean of the Calgary and Vancouver Campuses, helping many baristas and business owners realize their dreams. After more then a decade of Teaching while learning alongside some of the best International and National champions, the SCAA thought to award and certify Les as a Lead Instructor in 2012. Les has been a keen student of all things coffee since the 90’s. Les was the Canadian National Body Representative and the Head Judge for the Canadian Barista Championships from 2004-2015.
In this conversation, (audio here) Les and Greg discuss the early days of the Third Wave Coffee movement, the current state of the industry, and the dangers of forgetting where we have come from.
They cover what the Scace device is, how it was created, and how important it is for controlling the quality of espresso machine performance.
The Scace device helped to create and verify a temperature stability standard of plus or minus 2 degrees Fahrenheit as the minimum accepted variance in temperature. Prior to this, machines were routinely +/- 15 degrees F or worse, and yet everyone was still buying machines , thinking they were good machines, but in fact irresponsibly inconsistent.
As two key figures in the evolution of Specialty Coffee in North America, this is a pivotal interview for the historical record and for guiding the next generation of baristas.
Our Deleted Coffee History
Les: You and I first connected in the alt.Coffee forums in the early 2000’s. Some of that community history, from 2000 to 2003 is missing from the web. The genesis of third wave specialty coffee started in that forum. In a very short period of time, we had a community spring up, exchanging information and ideas, that were tested and tried by all of us. This quickly sorted out the untested myths and solidified what was relevant and useful, this saved everyone a lot of time.
It would be a tremendous loss if we can not recover that span of our history. (Note to reader , alt.coffee archives have literally gone missing since newsgroups were taken over by Google.)
It’s not just the Alt.Coffee forum that has gone missing. Also, independent and personal coffee blogs are being abandoned and deleted. There are the Wayback Machine backups, but, that is not just a simple google search.
At the Academy, we are proud of our history, who influenced us and would like to give credit to those who made significant contributions. Which is why I am reaching out to you specifically.
Every few years there is a new generation of barista. If our history online is gone, how will the new barista know the key players and terms that are relevant?
Otherwise, we are just a bunch of weirdos, in our basements playing with coffee, grinders and machines.
Greg: Alt.Coffee forum was great, it was the first time I had interacted with people on the internet. I would spend half a day writing and then post it from my work.
Les: I put up an aura that I was working in my office, but really I was posting on Alt.Coffee too.
An integral part of our courses at the Academy is to demonstrate the Scace thermofilter showing its importance for the barista and coffee roaster alike. We mention that your last name is both a verb and a noun which makes you world famous!
Greg: Like Crapper ! ha ha ha ...
Les: Ha ha yes... We have questioned many Fourth Wave geeky baristas, and surprisingly they have not used or heard of the Scace.
In comparison, you can’t fix cars today, if you don't have the proper Diagnostic Tool to read the car computer. It’s similar to the measuring of the temperature of your machine, if you don't have a calibrated scace how on earth does anyone set up an espresso machine?
Possibly worse, there are coffee technicians that don't own a Scace.
We recognize that as educators, we need to do our part , bring awareness to what's important again. And at the top of the list, is the Scace device.
The Invention of the Scace
Les: How did you get the idea for the Thermofilter device? Why would you want to measure temperature at the group head and then create the device to take that measurement?
Greg: This goes all the way back to David Schomer. David designed a method to measure temperature in Espresso Machines. His work was pivotal for my later design. He was convinced that the swing in temperature was affecting the taste and appearance of the espresso. He measured the temperature by burying thermocouple leads in the coffee cake within the filter basket measuring the temperature while brewing espresso. With my background in measurement science, I saw a problem with David’s method. Dry coffee grounds are naturally colder than the brewing water temperature and absorb heat from the water, which means we were not getting an accurate read of the machine temperature over time. We were getting a temperature read of how the coffee was absorbing the heat.
Besides, David’s method was really messy because you would get water and coffee grounds sputtering out the sides and bottom of the portabasket.
The critical measurement is the temperature of the water before it hits the coffee.
Troubleshooting the first Thermofilter
So I made myself a tool that didn’t absorb a lot of heat, which is the plastic part that mimics the coffee cake. I then added a little needle valve with a thermocouple wire glued in. My first attempts were quite crude. I then realized the machine had to be super clean or it would plug up the scace. A filter was the solution for that. Then Terry Ziniewicz said "you should make these”. I wasn’t an entrepreneur like he was, so I said, “you think anyone would buy them?”
Well, d’uh! So I made a couple and sent them to him at Espressoparts.com in 2004, and that’s how it all got started.
Les: The first time I heard of the Scace, was at SCA in 2005. Barry Jarrett from Riley's Coffee and Fudge was taking measurements from many Italian espresso machines on the tradeshow floor and showing that they were plus or minus 15 degrees!
Greg: Up until 2005, very few manufacturers building espresso machines realized their machines were fluctuating by +- 15 degrees. Either they didn’t know or even worse they didn’t care because their machines were still selling. There was no protocol, nor was there a device to measure what was happening at the shower screen. And still today, 15 years later, many coffee machines are still in the Dark Ages.
Les: I still get blank stares when I talk about temperature stability. This should have been solved in 2005 with the advent of the Scace. It’s like we are still arguing whether the earth is flat or not.
Greg: Oral and written history needs to be re-told over and over again or people growing up now will not know.
I grew up in the 60’s and 70’s on the United States side of Lake Ontario. There was a lot of acid rain back then, with dead lakes in the Adirondack Mountains and very few fish living in them. Acid rain was killing all the fish. At some point, scrubbers were installed on all the coal fired power plants in Ohio and Southern Canada and the acidity of the rain was reduced. After that, native fish were reintroduced and they thrived. My point here is that folks who don’t understand the value of environmental regulations that fixed the lakes will be more than happy to relax those regulations, not knowing of their benefit.
Les: Right. There's so much information now, that we forget quickly. Things that were once so important are suddenly discarded and forgotten. Case in point, tampers.
Recently we had a Barista Jam. One of the prizes was a Reg Barber tamper. Reg is a trailblazer, innovator and deeply generous in the specialty coffee scene. Strangely, the new generation barista picked cheaper prizes before finally someone took the $100 tamper. It was almost like a consolation prize to them.
Greg: Is Reg still able to make tampers?
Les: I’m not sure.
Greg: It says on Sprudge that he got tariffed out of business?
Les: I don't know if it was tariffs, pricing, or a change in brand awareness. I'm seeing this as the canary in the Coal Mine. Reg is an iconic third wave coffee brand, possibly in jeopardy. Which means, all aspects of Third Wave Artisan coffee are in trouble.
If we don't retell and share our history, then we risk becoming an afterthought.
The Engineering of Espresso Coffee Extraction
Les: What is the significance of the Scace device?
Greg: Dissolution of coffee, the process by which ground coffee goes into solution, is driven by 3 factors;
- surface area,
- and how much coffee is already in the solution.
For example, if you have pure water going by dissolvable coffee compounds, then there is a strong affinity for the coffee to dissolve into that pure water, and be transported away. If the water already has dissolved compounds in it, then the affinity for the coffee to dissolve is less so. That’s called the concentration gradient.
The rate at which things dissolve is an exponential function of temperature. This explains why Cold Brew coffee takes so long to extract.
If you want to control the process of brewing to within 30 seconds or less, as you would with espresso, then you need to control the temperature. Surface area is controlled by grinder technology and water is controlled by filtration technology.
The significance of the Scace device is that It allows you to measure and know the temperature of the water, where it hits the coffee.
Schomer was right about temperature and how it affected the taste and appearance of the espresso. But, he was wrong in his placement for measuring temperature in the coffee cake and the bottom of the portabasket.
Hot water gives energy to the coffee grounds making the measurement of the coffee cake incorrect.
Hot water loses energy when it moves through the coffee cake and into the bottom of the portabasket. It will simply be colder. If you measure with a thermocouple at the bottom of the portafilter spout, you will get a completely different answer than above the coffee cake.
The important measurement is right before it hits the coffee, when it can’t gain or lose any more energy.
It’s when the water comes out of the dispersion screen above the coffee bed, that the temperature measurement is crucial.
Even upstream, within the espresso machine boiler doesn't matter that much because it too will dissipate energy along the way to the group head. We really only care about the temperature of the water right at the moment it hits the coffee, at the group head.
Les: Before your device, there were many arguments about how and where to measure temperature.
Some people tried using styrofoam cups and meat thermometers and others were trying to build other Monty Python-like devices. These were very creative, yet lacked any scientific credibility.
As a scientist, you must have been inspired to create because of this pseudo device making?
Greg: Yes, those tools all had some merit, but were difficult to set up standard testing that was reproducible, measurable and consistently accurate in measurement taking. I was purely motivated by wanting to know what the temperature was and needed a device for that desire.
Measurement tools have been around in Industry for awhile, and have actually solved industrial problems in a way that's almost seamless.
The Industry tools I am loosely talking about would be a combination of my device, and Vince Fedele’s refractometer.
People like to argue about refractometry and taste. In my opinion, you should be tasting and measuring because there's a pretty damn strong correlation between total dissolved solids (TDS), temperature, and pressure, and what you're going to get on your taste buds.
Essentially, the refractometer and Scace give you the ability to establish boundary conditions ahead of brewing, and then measure the coffee coming out.
Les: Is there anything more than tracking measurements of heat and mass transfer in coffee extraction?
Greg: Conceptually, coffee extraction is not that hard a process to understand. But, in actual fact, it’s not an easy process. When you start to dig into the science of it all, there is really nothing else to pay attention to, other than heat and mass transfer. But the actual implementation of the concepts becomes quite complicated.
Les: In 2005, did you anticipate the influence of Scace Device on the coffee industry at that time?
Greg: No, I had no idea. Like I said, I’m not much of a self promoter, so it was completely natural and organic the way people found the device and started to use it.
Les: I remember, it was November 2007 and I was attending the first World Barista Championship temperature stability testing in Vancouver, on Granville Island.
You were there, but since then, looking at all the new espresso machines designed specifically using the Scace device…. Your tool influenced a whole new generation of espresso machines!
Greg: Yeah, so that was cool!
Les: Arguably, you changed something that hadn’t changed in Italy for approximately 40 years prior.
Greg: That surprised me, how little innovation and engineering was going into making espresso machines and how they could be improved so easily by people at home. At that time, in the early 2000’s people at home were modifying their espresso machines and they were more stable in temperature than their commercial counterparts. Do you know of any other industry that at-home users can dive into like that ? And, quickly the home user was getting their hands dirty and improving the machines so easily. It was an exciting time.
Les: People do hack stuff up, but in this case, guys at home were suddenly pulling better quality and more predictable shots than people with full-fledged commercial machines.
Greg: There is a lot of science and engineering in coffee today, particularly on the agricultural side. But, in the early 2000’s, temperature stability was not getting pushed hard by scientists and engineers.
Les: There is still a lot of that pseudoscience in the barista side of things. How do you feel about that?
Greg: Yes, there is a lot of pseudoscience in the barista writings and how they perform their job. A few years ago, Cosimo Libardo invited me to give a talk on coffee science in Australia. Cosimo was working in Australia at the time, putting this series of talks together for the specialty coffee industry. I gave a talk on diffusion, extraction science and its applications to coffee brewing. It was a simple talk on a pretty complicated subject, which seemed pretty well received.
Les: What is extraction science?
Greg: It was clear to me that most don’t understand the mechanics of how the dissolvable solids go from the ground coffee into the cup. Fortunately, there are people like Dr. Chahan Yeretzian, he’s the Swiss chemist working on coffee. He’s a really cool guy and is driving this research forward.
Basically, there is a cellulose matrix within the raw coffee bean that gets the shit beaten out of it by roasting, until it’s altered cellulose and dissolvable compounds - a thousand different ones or so.. Extraction science deals with how those compounds get dissolved into the cup.
Temperature Stability Testing
Les: Arguably, we have more espresso machines that are temperature stable, especially in home machines, in part due to the invention of your device. However, there are still many commercial machines on the market, that are sputtering at plus or minus 15 degrees. Unfortunately, salesmen are still finding ways to sell those machines to people that are clueless about the effect of temperature on coffee tastes and how it ultimately creates an inconsistent customer experience affecting your bottom line.
I hoped that the published results of the first ever WBC temperature stability testing that you conducted in 2007 would be the great leveller of machine manufacturers. Those results should have put public pressure onto the manufacturers to comply with temperature stability standards. Was there a ban on publishing the results?
Greg: Manufacturers were laying their chests bare in front of their peers at our first temperature stability testing in 2007. That’s not normal in the industrial world. Businesses tend to keep their secrets close to their chests. Their business could live or die based on publishing those results. All the manufacturers got their own data from our testing and were permitted to do whatever they wanted with that data.
(Editor's note : Is it possible to have WCE release that information with redacted manufacturer headings ?)
Les: Do you still conduct the WBC temperature tests?
Greg: I perform those tests every 3 years as a volunteer engineer/member of the Qualified Testing Committee of the WCE. In each subsequent testing cycle, we revisit and reevaluate and refine those testing protocols. As you may remember, in 2007, we did all this temperature measurement stuff thinking we need to correlate the results to how we make coffee. We spent a day floundering around, going through a ton of coffee, trying to figure out how the hell to evaluate machines.
Our main focus was to figure out what makes machines good. We took that primary idea forward to the next period of testing 3 years later and continued to evolve. By 2011, 2014 and 2017 those protocols were refined by the volunteers on the Qualified Testing Committee, and machines started improving–dramatically.
Each testing period we also looked at usability. For example, steam wand usability and performance, does the machine misfire, do the touch screens work if your fingers are wet, and in general, does the machine have poor ergonomics. And we’ve taken a fairly systematic approach to quantitatively understanding how reproducible a machine’s performance is.
So in the instance of temperature and pressure, uniformity on the front side drives the extraction process but there other variables in the extraction process that can be problematic. For example, how does the water percolate through the coffee bed, what kind of filter basket is being used, what is the spray pattern, etc,?
Filter basket holes and hole distributions are measured using advanced machine vision technologies prior to extraction yield testing . Yield testing is performed using a coffee refractometer and plotted on a universal brewing control chart. During the 2014 and 2017 testing sessions, temperature and pressure reproducibility, and filter imaging correlated well with the final extraction yield results. We still can't, with these tools, completely understand the brewing space, but you can do a remarkably good job with them and the results show in the cup. If candidate machines have the brewing space nailed down well, then we arrive at our recommendations to WCE based on ergonomic factors.
You can look at this using a refractometer for the bulk answer and you can taste it. This lets you arrive at conclusions that make one machine preferable to another in ease of use.
We’ve done a pretty good job of test protocol evolution. Now we’re trying to tackle coffee grinders, which are harder to test because the equipment to evaluate is far more expensive, and because coffee is an organic material and is not necessarily stable after grinding. With respect to the last point, understanding factors that affect instability are of interest to me. We know that temperature plays a part, but I suspect humidity does as well.
Les: Are any of these protocols public, or are these proprietary and secret?
Greg: I don't really know the answer. I have the ones from the last time sitting on my computer and nobody told me I couldn't send them out.
Les: You have my email right?!
We’d love to see your new protocol. Obviously you've written something up that allows you and your team to evaluate step-by-step each machine.
Greg: The temperature protocols are remarkably stable over the years.
Les: We ran the Canadian Championships from 2004 to 2015 using our own flushing routines. The WCE method takes about 35 minutes to complete, and that’s not really practical if you're trying to adjust temperature quickly in a competition setting. If the machine is good enough for the WCE, then how it performs during the intermittent duty cycle would reasonably be close to making coffee in a cafe setting. Of course, as long as you’re not purging it for 50 seconds.
Generally we tried to follow a routine for competition that would be more typical of cafe usage. It would be helpful if you authored a protocol that a technician could follow. For example, the protocol would address how to go about testing each group head.
Greg: I guess I’m a shitty business person, I’ve been making these devices for years and I still don’t have a manual for the end user.
Les: Firstly, we need to describe what a Scace is and does. Secondly, we need to teach how to use it properly, because Scace abuse is rampant.
Greg: There’s two camps. There’s people that buy and I never hear anything from them. That’s the majority. So I’m assuming they’re happy.
Then there’s people that use them and beat the shit out of them. They use it as a jack stand for their car or something.
Les: I may be guilty of one of those infractions.
Greg: It’s a fragile and delicate device. It needs to be treated with care. Think about how it is constructed and works. There’s not a lot of water that comes through a coffee machine, so if the temperature probe is too big, then it absorbs energy and you don’t get the right answer. You need to get the temperature really quickly as this process is only 30 seconds long.
In the engineering world there’s a term called response time. This is the time for something to move 63% of what it would move. For a thermometer, it’s the time for it to move 63% of the total change to a stable temperature. After 10 response times, you’re within a fraction of a degree of the answer. But that’s 10 response times…
So if your probe’s response time is 2 seconds, you don’t get to the right answer until 20 seconds have elapsed and now you’re almost done.
That’s why you need a really small, light-weight temperature probe, which is fragile. The one in the Scace is only 2.5 mm in diameter for the sheath. The wires inside are 5 thousandths of a millimeter. The response time is a quarter of a second. For 10 response times, you gotta wait 2.5 seconds. That’s adequate for the measurements we are recording.
But you can’t buy a thermistor or a platinum resistor thermometer that has a quarter of a second response time. They don’t make ‘em. There’s a new material called graphene. Graphene makes temperature sensors really fast. But graphene is hard to get hold of and it’s expensive. Scace devices are already expensive, not many people will buy them at 10 times the current retail price.
Les: Recently, I've seen knockoffs of your device and tried to calibrate it against your device, but there’s a substantial offset required. Anyway, I tell our students that the temperature should be staying constant during brewing. If a salesman badmouths the Scace Device, then we recommend walking away. If a salesman doesn't have a Scace, then we recommend running away! We maintain our objectivity about the various brands of espresso machine manufacturers by recommending “Scace it’.
How To Calibrate Your Scace
Greg: Calibrate them in the steam above boiling water because the steam is at a constant temperature to about .05 of a degree C. (Editor's Note: Have a look at this for more in-depth instructions and pointers.
Les: Again, one of the things that scares me about the third wave coffee movement is moving backwards and losing our progress.
I consider this as a long-term skirmish between the forces of Third Wave coffee and Second Wave coffee, and I hate retreating when we've gained ground. I want to reinforce where we've been, making sure that we don't take anything for granted since our biggest enemy is complacency.
If we don't record these stories of where we came from, then we can’t expect the next generation of baristas to even pick up from where we left off?
Right now, I'm seeing a dumbing-down of the baristas in the industry, because I would argue that the coffee geek that spawned all of us doesn't exist anymore. Or it exists in much lesser numbers, people are just not as motivated or as inspired to dig deeper into the mysteries of coffee. It’s easier just to work in a coffee shop rather than play around the basement with a couple of hand grinders and a couple of tricked-out home machines.
Greg: I think in some ways that’s okay…
Les: But we don’t want to reinvent the wheel. I'm kind of saying that we’re forgetting what the wheel is.
Les: Anything else that you'd like to say regarding this Scace adventure?
Greg: Manufacturers have said that temperature problems have been solved. I can reassure you that those problems have not been. In the quality control world, you need to verify if they have been. This has not been done.
Les: Even with machines that are known to be stable, in the preparation of the machine before it goes out to clients, I don't see an established protocol for calibrating and testing these machines.
Greg: Slayer tests everyone. They buy a lot of Scaces.
The guys that you know are really on top of their game, they use a lot of them. They’ve solved these problems. But as an end user, you don’t know if the temperature probe is going bad.
Les: I think that's sort of where my frustration with everything is. We're even forgetting that this is a thing to worry about.
In my argument, every roaster needs to have access to a Scace device if he's going to set up a client with coffee, to firstly make sure that his machine is calibrated to the temperature that he thinks it's at, and secondly, check his customers’ machines are calibrated to the same level. It's part of the toolkit of a coffee professional. I don’t think you can call yourself a coffee professional if you don't have a calibrated one in your toolbox
Greg: People don't want to use measuring tools, mostly they want taste to be their guide. But if you have a certain coffee and a roaster says you should brew it at this temperature and pressure and it should be at this TDS value and you should get this taste, you should use all the tools that are available to you, right? That makes sense!
Les: Right. To benchmark your palate so to speak.
Greg: Well if it doesn’t taste the same, there's a problem, that's for sure. If you’re getting a certain taste result that you like, the drivers of it are going to be the temperature, surface area, and concentration gradient with pressure being involved in the surface area. Temperature and pressure are the variables, and you need to know what they are doing on the upstream side and what the TDS is on the downstream side. That is the essence.
Les: But you left out how I move the coffee around with my finger… (laughter)
Greg: Yes, distribution depends on the dirt under your fingernails. Ha ha!
Les: My running joke is, I wanted to make a business of distribution tools, by taking the live cast of World Barista Champions’ index fingers. Maybe, I could start off my new venture with your fingers Greg? We’ll call your finger the ‘engineer finger’ dosing tool. Or ‘Scace’s finger’ dosing tool ! And, we will even allow you to pick which finger to cast.
Looking for Archives of the Good Old Days
Greg: I want to go back to our earlier conversation on the lost archives of the forums…
Most of the innovative work that was really interesting was accomplished in early 2001 in about a 4 month period. And from 2000 to 2004 all of the PID (Proportional-Integral-Derivative) experimentation and implementation was completed.
Les: I refer people to that, but now we can’t even show them that. The history is obscured online.
Greg: That’s really weird. Randy Glass archived a bunch of stuff. I know he’s still around. He’s a retired graphic artist and a coffee guy. I'll ask him if he’s got copies of that shit cos they’re not findable on the internet now.
Les: Well, thanks Greg. It’s been a walk down memory lane, but also a chance to trace back how we got here. I’ve never been a history buff, but I realise the significance of it now. I know, if we don't know where we came from, then we don't know where we are or where we're going...
Greg: Right. It all gets forgotten and then you’ve got to reinvent it or something. But what would happen if suddenly we didn’t have computers anymore. For example, what would happen without Babbitt bearings?
Les: Was that a comedy team?
Greg: No, not Lorena Bobbitt!
It was invented in 1839 by Isaac Babbitt in Taunton, Massachusetts. It used to be the way that you made bearings in car engines in the early 20th century before the thin shell bearings in crank shafts now. You would pour this material and fit the crankshaft using a deformable material that would flow out and you could measure the clearance between this bearing material and the ground joint. If you couldn’t get those parts, no one would know how to make bearings any more.
Les: The only good thing about getting older is I can fool the younger people with the old magic tricks.
Anyways, great speaking with you Greg!
Greg: Thank you for taking the time to speak with me today.
We would like to give special thanks to Terry Ziniewicz,Barry Jarrett,Randy Glass,Dr. Chahan Yeretzian, Vince Fedele, Reg Barber and Les Kuan for their fact checking, suggestions and overall enthusiastic contributions to this interview.
VisitEspresso Parts to purchase a Scace Device.
If anyone can access alt.coffee archives, here are the article links saved by Randy Glass (which no longer are available). Please email us if you are able to access these files:
Feb 4 2001, 12:43 am
Temperature study of my Sylvia (looong)
Feb 5 2001, 12:50 pm
Proportional Temperature Control for Sylvia
Mar 5 2001, 6:32 am
PI Sylvia Tempmeasurements (really)
Mar 24 2001, 2:39 pm
SCHOMER'S # 27
Prof. Brian L. GOMES da COSTA
May 21 2001, 5:41 pm
Tricked-out Silvia part 3: Procon pump!
Apr 15 2001, 1:10 pm
Sep 20 2001, 1:03 pm
Tricked-out Silvia: heated brew head
Sep 16 2001, 4:26 am