#pocketscience

I’ve recently installed insulation on the exterior of my Quest M3. I’ll offer some thoughts on it in terms of the Quest and also some broader connections on how it seems to be affecting the roast, and in that sense, I think it’ll be useful even if you roast on a different setup.

the job

Specifically, I purchased these items from McMaster Carr. I found some instruction from Tom Chipps on Home Barista. (Just to be totally clear, I’m listing these so you can find them. I’m in no way paid by McMaster Carr.)

9379K93 Ultra-High Temperature Foil-Faced Insulation Strip, 1/2" Thick, 3" X 12' 1

7631A92 High Temperature Aluminum Foil Tape, 2" Width X 5 Yards Length, .006" Thick

I put on rubber gloves and an N95 mask, cut the insulation into measured strips - just two strips needed - taped them together, and voila. It took less than thirty minutes. The insulation is fiberglass, so please be very careful and take the necessary precautions. Don’t eat it, snort it, or inhale it. I’m not responsible for your mistakes, so read up.

experience

In concrete terms, the results are pretty apparent. I like to think of MET as a sort of speedometer for how quickly I’m roasting. (This analogy isn’t quite perfect, since our acceleration is always relative to the current bean temp. Therefore, MET-BT would be more precise.) With insulation, at a given MET, the roast now proceeds more quickly. In other words, BT increases more rapidly or BT RoR is higher. This is excellent, because it means that I can roast faster if I want to, and I have less risk of scorching coffee. 

Clearly, I’m retaining heat in the drum better. [A bit of pocket science ensues...] Energy is less concentrated around the heating element and better distributed through the drum, so more heat is transferred convectively rather than conductively. Since the M3 tends to be quite conductive given its airflow pattern, this is excellent.

negatives

The first downside is that it can be difficult to slow down the roast. I typically enter 1c at around 490 F MET and finish my roast around 460-470 MET in order to get a declining RoR in 1c. (This declining RoR in 1c is extremely important for avoiding baked flavors, in my experience.) Before, moving through ramp at 490 MET would produce a ramp time of ~3:45, 495 around 3:15-3:25, and 500 around 3:00. Now I move through it in closer to 3:00 even at 490. So I’ll now have to implement a more complicated strategy like not reaching max MET until further into ramp. Fortunately, I generally favor pretty quick ramp times to avoid malty and bready flavors, which I detest in coffee.

This problem also crops up during the “drying phase” or “green phase,” as I’d rather call it. The roaster now moves through it even more quickly. However, since I haven’t been getting scorching, I think that this is just an apparent problem rather than a real one. If, as is typically thought, there are no chemical reactions occurring in the drying phase, then it’s OK to move through it as quickly as we can without scorching.

The other problem is on the roaster side of the tryer. Any adjustment to a roaster forces the roaster to relearn some procedural memories [”muscle memories”]. In this case, there’s the added issue of electric and thermal lag. Electrical elements take time to heat up. But we don’t control heat directly, we control amperage. So the electrical element responds with some lag, as those of you who’ve cooked on a traditional electric range know. (This is why I love my induction burner.) When you add insulation to the equation and increase the thermal mass of the roaster, this gets to be even more of a problem. It’s not insurmountable, but it’s definitely a bit of extra work on the roaster’s part. It’s really key to pay attention to the MET consistently and develop a feel for the momentum of the roaster and heat added if one intends to manage it effectively.

ideas (a.k.a. useless speculation)

So this leaves us with some thought-food. Adding insulation or otherwise increasing thermal mass probably offers an increase in convection over conduction. Convective roasting, at least to a point, offers more even bean development. This means I’ve been managing good development and refractometer-measured solubility at 11.5% weight loss and even less, versus 12% before. This isn’t to say that I always roast quite that light, but I can if I want to. 

A double-wall drum roaster with plenty of thermal mass is somewhere near 80%/20% convection/conduction. These roasters achieve excellent and even development if used properly. A recirculating drum roaster (e.g. Loring SmartRoast) is even more convective. An air roaster is essentially fully convective. The familiar problem of convection/conduction balance is a (conductive) pan roast searing the outside of the bean and leaving the inner bean raw. The unfamiliar is an air roaster managing to roast the inner bean darker than the exterior in an extremely fast roast. (By the way, I’m just suggesting that these issues tend to crop up at extremes of convection/conduction balance, not that these problems are necessarily caused by convection/conduction balance.)

Either of these is problematic, but with increased thermal mass, it appears that the M3 has better heat transfer characteristics. 

The other area for improvement would be in terms of airflow. It would be great to have airflow push heat through the bean mass and then out of the roaster. As is, the two processes are pretty much disconnected. A possible addition of a heat gun in the tryer slot or a modification to the exhaust pathway could be a great improvement. But, one step at a time. For now, better developed, sweeter, and cleaner roasts.

intro

As with my last espresso nerd post, a quick shout out to my friend Mandy who suggested and carried out part of this experiment.

Anyway, a while back, Perger suggested that correct distribution should maximize extraction yield. Better distribution means more even extraction, and since coffee extraction is increasingly harder as it progresses toward maximal extraction, more extraction should tend to be more even extraction. Lo and behold Perger comes out with an article with a different methodology, basically figuring out which distribution packs the most espresso into a given space - interesting, but not quite what was intended.

By this point, we had already conducted some initial investigations, not finding even a shred of support for this idea, so we guessed at why he’d changed his methodology and designed an experiment. Here are the basics of our methods:

methods

We were using a Linea at 9 bars and 199.5 F at the grouphead, grinding on a Mazzer Kony, .1 g scales for dosing and shot weight, espresso at eight days from roast. Shots were thoroughly mixed, samples taken, allowed to cool, VST Lab 2 refractometer purged, and measurements made until stable. We used the standard .45 micron syringe filters. The refractometer was regularly zeroed with DI water.

For distribution, we moved the portafilter to achieve even distribution, tapped horizontally to achieve a flat bed, tapped vertically twice, and then tamped. For non-distribution, we used a mound of ground right in the center of the portafilter.

We also stuck to a given output weight as closely as possible, since brew ratio has a gigantic impact on espresso extraction. This would be easier with a volumetric, but we were able to achieve pretty consistent output with the help of a scale. We used 17.5 g in a VST 18g basket, approximately 33g out in around 33 seconds.

We pulled five shots for each condition. 

results

We found no obvious effect on extraction yield from looking at the data, and I ran these numbers through SPSS (two-tailed independent samples t-test) and found no effect (p=.2). Obviously, the study didn’t have much statistical power, but if distribution affected aggregate extraction yield that strongly, then you’d see it even in this tiny study. On average, the non-distributed shots actually tended to be slightly more extracted. (Again, this wasn’t statistically significant.)

Raw data are available here: http://www.mediafire.com/download/974fm2i3o8vy5bh/results+spro+dist.zip

Visually, distributed shots were a bit more even and tended to converge to one stream more rapidly. However, they weren’t quite as ugly as you might expect.

In terms of taste, distributed shots were a bit sweeter, but the effect wasn’t as dramatic in this regard as you might expect. (Yes, this was unblinded.) (Pocket science explanation: non-distributed shots extracted heavily from areas of channeling or “micro-channeling,” and thus had less opportunity to extract sugars from areas where channeling didn’t occur.)

In terms of mouthfeel, distributed shots had slightly better viscosity. Again, this effect wasn’t dramatic. (Pocket science explanation: more of the puck saturated more evenly allowed for solids to be extracted from more of the puck.)

conclusion

Refractometers are awesome but won’t replace your palate. They can’t measure everything. 

[front to back: La Marzocco 58.0 convex, “the wedding tamper” 58.4 mm, Pergtamp]

First of all, a shout-out to my friend Mandy for coming up with this idea and pulling a bunch of shots. The idea itself was simple: replicate (or fail to replicate) Perger’s claims of tampers’ effects on extraction.

In practice, we just dialed in the espresso in a typical qualitative fashion - winding up at around 17.5 (to the .1g) dose and 30.0 output in around 28 seconds. We tried to maintain these parameters but wound up fluctuating a bit. In any case, the claims I make will be very basic, and future, more extensive tests can produce more concrete and conclusive results.

We were using a Linea at 9 bars and 199.5 F at the grouphead, grinding on a Kony, .1 g scales for dosing and shot weight, consistent grooming and distribution technique (even dose, swipe, tap), espresso at six days from roast. Shots were thoroughly mixed, sample taken, allowed to cool, VST Lab 2 refractometer purged, and measurements made until stable. We used the standard .45 micron syringe filters. The refractometer was regularly zeroed with DI water.

Two effects were very obvious: 

1) Brew ratio has a gigantic impact on extraction yield. This effect dwarfed any impact of shot time. 

2) The smaller, convex tamper yielded dramatically lower extraction yields. We did some additional comparisons after the fact to a 58.0 flat tamper and couldn’t conclusively state whether it was worse - better sampling methodology and stopping shots by weight very precisely would be required.

So this is to say the Pergtamp performed similarly to a 58.4 tamper. Both performed dramatically better than a convex 58.0 and likely slightly better than a 58.0 flat. This isn’t saying it isn’t better, just that the effect isn’t obvious in a statistically-weak experiment.

Raw data are available here. We pulled many other shots that aren’t included. 

We also performed some tests with a 58.0 mm reg barber flat tamper, shown above.

We investigated two extremes of distribution - on one end, literally no effort whatsoever, not even portafilter movement. On the other end, a pretty meticulous standard involving even distribution into the basket, a finger swipe, and taps. Surprisingly, there wasn’t any obvious effect on extraction yield. The sloppy shots tended to channel a bit but were nowhere near as bad as expected. They also tended to run a little longer due to channeling, so the extraction yields were higher due to the size of the shots. That is, the effect of brew ratio on extraction dwarfed any effect from channeling.

I’ll definitely return to distribution later, with a larger sample size.

A couple other observations:

1) The conical Mazzer Kony actually had no trouble reaching correct extractions when pulled around 60% or longer - coupled with a properly fitted tamper, good technique, and so on. We could achieve 19-20% extraction when pulling long-ish shots (50%).

2) A far larger impact was noted from a convex bottom than a difference in tamper size. While the Pergtamp may be better than slightly smaller options, its effect would need to be examined in a more powerful study.

3) There was no obvious effect of time. And, again, brew ratio completely dwarfed time as an influence on extraction yield. We got “correct extraction” in terms of extraction yield with shot times as low as 20s (!) and underextractions at 33-34 seconds. 

And a plan for another experiment:

5 shots for each condition, up from 3, ended at precisely 1:2 (50%) brew ratio. 

i) tamper size: 58.0 (common), 58.35 (common custom VST size), 58.5 (perg)

ii) distribution: literally nothing, even distribution and two vertical taps (”minimalist”), even distribution, swipes, two vertical taps (”maximalist”)

[here’s a picture! now you’re entertained! now read a big wall of text!]

Back when I first got into coffee, I remember reading through a gigantic list of helpful threads on home-barista. So in that same vein, I’ve composed a mega-list of essential reading. Most of this is online. This will never be complete and will occasionally get updated.

Scott Rao (Roaster, barista, writer) - Read all his stuff. If you roast, start with the Roaster’s Companion. Everything but Espresso is probably the single best introduction to extraction dynamics there is. The Professional Barista’s Handbook should cure you of most of your bad habits as an espresso-head or barista. 

Matt Perger (Barista competitor, roaster, educator, and coffee thug)

EK Series (about the EK and why it’s great) 

http://mattperger.com/The-EK43-Part-One

Downward Spiral of Death (on why espresso roasts are often overly dark and espressos are often underextracted)  

http://mattperger.com/The-Downward-Spiral-of-Death#.VHv4JzHF98E

Extract more, better (The title says it all. If you aren’t extracting >20% from your coffee, you’re missing out on its potential.) http://mattperger.com/Extract-More-Better#.VHv4KTHF98E

V60 Method (I use this often, just with a slightly more dilute ratio) - http://mattperger.com/V60-Pour-Over-Method#.VHv4LzHF98E

Barista Hustle - Go subscribe to this right now. Matt posts easily-interpretable posts on coffee every week.

 http://baristahustle.com/

Ben Kaminsky (Barismo cofounder, QC’ed for Ritual, won the taster’s cup numerous times, coached Matt Perger to a 2nd place WBC)

On Espresso, a lovely video that goes into espresso extraction and how to make espresso actually taste pleasant. I consider this video a goldmine and have been meaning to post some notes from it, but in the meantime, go watch it.

http://nordicbaristacup.com/2013/11/ben-kaminsky-espresso-why-you-hate-it-and-how-to-fix-it/

James Hoffmann (WBC champ, big dog at Square Mile)

Double hump (one idea why underextraction sometimes tastes pleasant) -

http://www.jimseven.com/2010/11/08/the-double-hump/

French press recipe (why I use six minutes for my Aeropress brews) -

http://www.jimseven.com/2010/11/04/cupping-vs-french-press/

Extraction vs. Time in Cupping bowls (gets into the dynamics of extraction in immersion)-

http://www.jimseven.com/2012/07/12/cupping-protocols-and-extraction/

[another pretty picture! wow! this chemex looks like Jupiter with the great red spot.]

Sweet Maria's / Coffee Shrub

(This is really only useful if you roast.)

Stretchin’ Out the Roast (This goes into the effects of stretching out each phase of the roast; it’s also useful for thinking about which types of reactions and flavors are dominant in each phase. If you roast, I’d highly suggest replicating the results as I have.) - 

http://www.coffeeshrub.com/shrub/content/stretching-out-roast

Using Sight to Determine Roast Level - (disclaimer: remember roast level != development; light roasts can be well-developed and dark roasts can be poorly-developed.)

https://www.sweetmarias.com/library/content/using-sight-determine-degree-roast

Roasting dry-processed coffee - 

http://www.coffeeshrub.com/shrub/content/fundmentals-roasting-dry-processed-coffees

Nick Cho (importer of the Wave, designer of the Brewer’s Cup and intelligent coffee nerd)

In-depth discussion of press brewing, with relevance to other preps - 

https://plus.google.com/106600757771848447744/posts/TxoVir91SoF

Home Barista (a lovely resource for those of you ready to graduate from /r/coffee, /r/roasting, and so on)

Home-Barista Espresso 101 (if you know nothing about espresso, start here. Otherwise, this might seem basic.) - 

http://www.home-barista.com/tips/espresso-101-newbie-introduction-to-espresso-t26435.html 

http://www.home-barista.com/tips/espresso-101-how-to-adjust-dose-and-grind-setting-by-taste-t16968.html

Other FAQs - 

http://www.home-barista.com/advice/faqs-and-favorites-t9793.html#p111420

Colonna & Smalls (a shop)

On grinding...

https://colonnaandsmalls.wordpress.com/2015/02/03/the-heat-is-on-more-grinding-puzzles/

https://colonnaandsmalls.wordpress.com/2015/02/01/grinding-the-dark-matter-of-coffee-a-think-piece/

(related, from h-b) - http://www.home-barista.com/grinders/why-are-conical-burrs-inherently-bimodal-t33252.html

David Walsh (coffee geek over at Marco/Uber) 

On grinding, a somewhat prophetic post - 

https://theotherblackstuff.wordpress.com/2011/02/16/the-dark-age-of-grinding/

A great post on evenness of extraction in different brew preps - 

https://theotherblackstuff.wordpress.com/2010/07/26/at-odds-with-unevenness/

Jim Schulman 

A technical article on espresso extraction, SOEs, and which variables have measurable impacts

http://coffeecuppers.com/Espresso.htm