Post By samuellaw178
Refractometer - too much science?
I read with interest the thread a couple of months ago about 'common sense vs technology'. I can certainly appreciate the overwhelming viewpoint that is essentially 'let your tastebuds do the talking', and not to get too bogged down in what many might regard as unnecessary technology.
BUT, I'm pretty geeky, love science and numbers (am currently doing a biostatistics degree) and like to maximise reproducibility wherever I can (usually with the assistance of whatever tools are available in a given context).
In the few months since my first posts here I'm regularly roasting with a Behmor and I recently bought a new machine and grinder and am working towards improving my espresso extractions. I'm now really enjoying the drinking of coffee as well as the art/science of optimising those shots.
For the person new to espresso extraction, there's a big learning curve - not only in the mechanics of pulling a shot (and there seem to be several 'acceptable' ways of doing this), but also in the diagnosing and fixing of issues when things don't go right.
Does having a tool like a refractometer put you in that ballpark of better extraction faster than fluffing around through trial and error? And perhaps then, more of the 'art' comes in to refine the process?
Or is this all too much science, too costly and becoming so analytical that it takes some of the pleasure away from coffee making (perhaps not for me :-)
Has anyone here used a refractometer, and has it helped?
I notice you can pick some up on Amazon (Milwaukee vs Hanna devices) for under $200. Don't know how accurate these are compared to the VST (but this is 7x the price).
Seems not many people here on CS actually geek enough to bother with a refractometer...
I have an Atago refractometer myself for a few months.
Does it help my shot getting better shot? Not really.
Does it help me to learn more? Yes.
Unfortunately, having a refractometer and hitting a certain % doesn't guarantee a good shot. From my own observation, your grinder, shot volume, grind size, filter basket, machine, coffee, roast level, water, coffee ground distribution/tamping technique will all affect the outcome of your refractometer readings. So what that means is if you get a bad number and you're still new in the espresso game, you probably wouldn't know what went wrong and equally clueless what to do next. Similarly, in the hand of an expert, he/she probably doesn't need that refractometer to tell what to do next (and it doesn't).
Only in the cases where the barista is so used to tasting his/her underextracted (sour) coffee (you will be surprised how many barista/coffee roaster could get their palate trained/adapted to like their own coffee even if it tastes unpleasant to others), a refractometer will give a nudge so that the person can experiment and try to improve their coffee. The palate and tasting experience can be very subjective so the refractometer can serve as a 'calibration' point.
In a home setting, if you can repeat your espresso process and keep getting the same number, it means you are consistent enough. It's a useful tool as trainer wheels in that sense. Don't use it to aim to achieve a Extraction Yield % in hoping to get better shot. Instead, measure your % so you know where you are in the extraction spectrum. Then deliberately increase or decrease the % (by adjusting grind size, and shot volume) to see if the taste improves. Often, if you change the coffee (different roast/origin), your achievable extraction yield % will be slightly different.
Refractometer to barista is almost like a temperature readout to a coffee roaster. Achieving a certain roast temperature target won't guarantee it's a good roast. But at least you know where you are (how light or how dark the roast is) and can adjust/optimize your roast next. Sure, a seasoned roaster can roast relatively consistently and do fine without knowing his number (roast temperature）. Similarly, measuring the TDS of your coffee tells you where you are in the extraction spectrum, but you still need to decide what to do with the number - don't let the number drives you instead.
About meter recommendation, there''re quite a few conflicting opinions about the Milwaukee and other lower end refractometer that read brix or RI. Some say it's passable, some say it's not accurate enough. For espresso and home use, I can recommend the Atago. It will read slower (takes more time) than a VST refractometer. But for espresso, it's precise enough to be useful. VST (3x the price) is overkill IMO and makes more sense for commercial setting (where time is money), not to mention the disposable syringe filters required to work.
Last edited by samuellaw178; 19th September 2016 at 08:19 AM.
Bang on Samuel.
I have an Atago as well and could not agree more with your comments.
Many thanks for that Samuel - appreciate your thoughts on the subject.
I'm tempted to even buy a cheapie optical refractometer to start with (although resolution is less) and see if it's something that I find value in using before considering the Atago.
No worries. I've tried the cheapo optical refractometer. No use as it's too coarse and not useful at all. The slightly more expensive digital refractometer might work okay but most likely you'll have wished you had spent a little more for the Atago. Instead of spending $200 now and ~$400 later, might as well spend the $400 now and move on with it (that's just me ).
If you don't mind spending a little (totally subjective!) and having an extra measurement/landmark to your espresso, the Atago is perfect. Spend too little and you get frustrated; spend too much and if you don't like it, it'll just be gathering dust or lose easily $100-$400 from reselling which is almost enough to buy an Atago. I see it as a very nice to have and a very informative tool, but not crucial to make good espresso. Maybe try without refractometry for a bit and see how it goes. If you really like measuring stuff and geeking like I do, it'll be great & fun.
Last edited by samuellaw178; 19th September 2016 at 11:40 AM.
Thank you - this is good to know. I wondered whether the resolution of an optical device was useful, but it doesn't sound like it is. I think I will skip it and give thought to whether I go for an Atago or not. I do have a lot of fun in measuring things which is why something like refractometry appeals to me (I'm also an optometrist in a previous life, so optics was my bread and butter for a while).
Originally Posted by samuellaw178
Do you still use your Atago or has it become a dust-gatherer? Do you use an app in conjunction with it? - e.g. VST Coffee Tools?
I still use it on and off. Mainly when doing some major changes in my coffee routine - ie trying out different grinders, baskets, dose, different coffee roasts etc. It's a nice tool for consistency checking as well .
Coffeetool is nice as it's a phone app. Ultimately, you can also calculate the yield using Excel on a laptop to keep a record. Extraction yield = TDS x shot weight/ dry coffee dose (value may be very slightly different to Coffeetool's as they consider CO2 etc as well, but not important for our context).
Originally Posted by pgseye
I shanghaied a friends medical laser refractometer (probably $200K worth, as that seems normal cost for most of his gear) for a long weekend a couple of years ago. We ran a mountain of espresso tests (and still ran out of time). No idea what cheaper ones are like in terms of accuracy. FYI, this one had one gotcha - if the particles were coarsely shaped (done deliberately by the owner as a demo) turning it around (or just shaking it up and down) and firing the laser in at different angles varied the readings markedly. Before we got serious, we proved that espresso readings were OK, however plungers weren't always consistent. BTW, we also used his 0.001g scales for the dosing (one single ground makes a difference to the reading!) which was a PITA to do, but actually helped a lot in terms of shot measurements & consistency.
I agree with Samuel's post - if you do not know what you are tasting for, it would probably just confuse the hell out of you. Which one of the dozen or so variables are you working on? It is really more of a lab test instrument - to the point that I suspect most of the CS / cafe* ones spend 99% of their time in a drawer somewhere.
Even after you know what you are doing with espresso I doubt it would rate much higher than curiosity after one session. I would suggest you find a cafe with one* and see if they will let you play with it (on site if necessary) rather than investing in one. It is unlikely to be heavily used.