Help Using DiFluid R1 Refractometer

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BaristaBob
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Joined: 6 years ago

#1: Post by BaristaBob »

Well the wife bought me a refractometer for Christmas. I don't want to geek out to much on extraction, been adjusting my coffees by taste since the beginning of time in this hobby...and as we all know extraction data isn't the end all to a great cup. However, I downloaded the app and it's not that intuitive as to using it. Anyone have this little device mastered? I can use it pretty well straight from the device, but the app screens get confusing, at least for me. Things like setting all the parameters getting to "test" mode? How to delete data you no longer need? Saving data? That sort of stuff. Maybe there is an online manual for it?
Bob "hello darkness my old friend..I've come to drink you once again"

Pressino
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#2: Post by Pressino »

I don't have any practical experience with the DiFluid R1, but I've been using their model R2 refractometer for a while and have a positive opinion about it. Previously I had used my Reichert AR200, an instrument with very good accuracy and precision for nD measurement over the range of 1.33000 to 1.56000, but which was a pain to use because it required using a program with lots of math to convert it to coffee %TDS. I didn't feel like spending $500+ to buy a specifically designed coffee refractometer with two decimal place %TDS resolution (like the Atago and current model VST Lab) and wasn't interested in buying any of the other less expensive units that displayed TDS resolution to +/-0.01...because their accuracy or precision specs indicated their resolution would qualify as mostly "empty" resolution.

Then I read about the R2, whose resolution, accuracy, and precision figures actually sounded attractive enough to spend $230. It sounded like it would give me the precision I could get from the AR200 but a lot more easily, especially given that the associated DiFluid coffee App allowed it too work in conjunction with a smart phone/computer and a DiFluid scale to monitor and analyze coffee brewed by any common method. When I first received it, I was quite shocked at how tiny it was and really began to doubt it would actually function as the manufacturer claimed.

So far, I'm finding that the R2 seems to work as well as my AR200. It holds calibration over days of use. I like the fact it can display sample temperature and the response time is quick. It is both precise and accurate. The SCA plots are nicely done and extremely helpful. I've actually improved my pour over coffee results based on what those plots showed. As regards the small size, that's something I now consider to be an advantage, but I still worry about durability. The prism window is made of glass, not harder material like saphire, so you need to be careful cleaning it. But so is the Atago's, as far as I know.

All in all, so long as it keeps on working as well as it has so far I think this is the first sub-$500 coffee-specific refractometer worth buying.

BaristaBob (original poster)
Posts: 1873
Joined: 6 years ago

#3: Post by BaristaBob (original poster) replying to Pressino »

After a month or so of using the R1 it has become easy to use. The app has also improved, as there has been two or three updates, making the app more intuitive to use. I've been impressed with the R1's ability to hold calibration as well, but I've not pushed it past a day since it is so easy to start the day zeroing it out. Day in, day out I'm impressed by its repeatability. I can say as well, it has made my espressos better. I use to think many of my shots were under extracted, only to find out that most of my shots have been over extracted (EY greater than 22%). I now use smaller doses, and pull more ristrettos than in the past. So it's been a win for me as well. A nice little device for $129.

One question I now have is how much effect does filtering my sample vs not filtered have on the EY value? I test unfiltered simply because it's way easier and the syringes cost a lot less.
Bob "hello darkness my old friend..I've come to drink you once again"

jpender
Posts: 3905
Joined: 12 years ago

#4: Post by jpender »

BaristaBob wrote:One question I now have is how much effect does filtering my sample vs not filtered have on the EY value? I test unfiltered simply because it's way easier and the syringes cost a lot less.
You'll have to do the experiment to be sure but past investigations have found that unfiltered samples tend to read a little high and also have poorer precision.

Here is a good example: https://awasteof.coffee/science/espresso-filtration/

I found this to be true even with my $25 optical refractometer. Unfiltered samples of espresso read about 0.3% TDS higher on average than the filtered ones. That surprised me because I had believed that digital refractometers read high because of the way their firmware might be confused by particles obscuring the total internal reflection edge. I figured that my eyeball wouldn't be as easily duped by the obviously fuzzier, less precise edge. But it's also possible that filtration actually reduces the dissolved solids content slightly in addition to removing tiny undissolved particles.

In any case I think that if you're happy with the precision with unfiltered samples it doesn't really matter if the absolute value reads a little high.

BaristaBob (original poster)
Posts: 1873
Joined: 6 years ago

#5: Post by BaristaBob (original poster) replying to jpender »

Thanks for the article, that's exactly what I was looking for, but couldn't find. And, yes...I'm happy with the results and the repeatability day to day. So it's nice to know that my values unfiltered are 0.3 to 0.4 higher, but I'm not trying to land safely on the moon either. I just want to drink great coffee!!
Bob "hello darkness my old friend..I've come to drink you once again"

jpender
Posts: 3905
Joined: 12 years ago

#6: Post by jpender »

I didn't do enough tests but I figured I could just add a fudge factor of -0.3% (for normal espresso strength) and improve the accuracy slightly. The precision clearly suffers as the dividing line is quite fuzzy for unfiltered and very sharp for filtered. You don't see it with a digital refractometer unless you do a bunch of tests to measure the precision. I don't have a photo of what I see in my refractometer but I did take a picture of the coffee itself: samples I dried in the oven as a check since that gives me values on par with a VST.

Filtered vs unfiltered is like clean water versus mud:


Oddly enough I prefer to drink mud!


From what I gather landing on the moon is pretty darn hard! Right up there with brain surgery:

BaristaBob (original poster)
Posts: 1873
Joined: 6 years ago

#7: Post by BaristaBob (original poster) »

Ha, ha...well sometimes I feel that making a great espresso is harder than rocket science and brain surgery put together! :lol:
Bob "hello darkness my old friend..I've come to drink you once again"