Anyone have one? DiFluid's initial model had good reviews. The new one, the R2, is supposed to be more consistent and need less frequent calibration. It is not a cheap product, $US240 but a discount to the $600+ ones.

I just remember reviews trashing the first model, e.g., Lance Hedrick's http://www.youtube.com/watch?v=yF2fIaQS70k

The reviews of both of the DiFluid models that I have seen/read used units supplied by DiFluid and so I ignore those given how electronic refractometers work. In addition, the ones by coffee people often seem to show an ignorance of metrology and/or statistics that is unfortunate.

In metrology I want to see traceable certification/calibration for the actual individual unit that I purchase. Known manufacturers of all manner of refractometers like Atago and Misco do this as a matter of course. (Misco makes the hardware for the current VST.) While a hobbyist probably doesn't need NIST-traceable certification, no mention of calibration/certification supplied with each individual unit is a red flag for me.

Caveat emptor.

Acavia wrote:Anyone have one? DiFluid's initial model had good reviews. The new one, the R2, is supposed to be more consistent and need less frequent calibration. It is not a cheap product, $US240 but a discount to the $600+ ones.

Suppose I had one and I liked it? What would that tell you about it's quality?

I've read one review of the R2 that was mixed. And there were a number of questions I had about the review.

The author liked to use the term groundtruth to indicate an ideal value. E.G., the TDS of instant coffee dissolved in water had a groundtruth that was presumably determined by accurately measuring the powdered instant and the water. I say presumably because there wasn't any discussion of this in the blog post. Is instant coffee 100% soluble? I have dehydrated syringe filtered coffee and then rehydrated it and found that the TDS dropped. Maybe something similar happens with commercially prepared instant coffee. Are all instants the same? In the case of Starbucks VIA there are small coffee particles added that are probably not fully soluble. Similarly one would have to ask if instant coffee has a moisture level of 0% and, if so, how long it would take to rise significantly once the package is opened. One can ask similar questions about the sugar that they used.

The R2 and the VST both read low for the groundtruth of the instant coffee they used which is what you would expect if the coffee were either not entirely soluble and/or had a non-zero moisture content. Maybe a coincidence.

I mention these facts not just because it may partially undermine the credibility of their study but because it points out the difficulty in evaluating these tools. If it were me I'd pay for the knowledge that the tool was well made and verified. The VST -- which they used as the groundtruth for some of their tests -- fits that bill.

Not quite off topic, but say as a home hobbyist I wanted to know if my extractions were going higher or lower when changing things like amount of coffee used, grind size, yield, etc...you get the point. Maybe the absolute value (use of a standard solution) is not as important as whether the R2 provides reproducible values? This becomes what's important to me.

For better or worse, the accuracy of an instrument is often correlated with the instrument's precision. While correlation is not causation, it doesn't make sense for a manufacturer to design a precise measuring instrument that isn't accurate, or to design an accurate measuring instrument that isn't precise. Users want both.

You get what you pay for.

BaristaBob wrote:Not quite off topic, but say as a home hobbyist I wanted to know if my extractions were going higher or lower when changing things like amount of coffee used, grind size, yield, etc...you get the point. Maybe the absolute value (use of a standard solution) is not as important as whether the R2 provides reproducible values? This becomes what's important to me.

Yes, of course, particularly when it comes to extraction which isn't a highly portable number.

But how can you tell how precise it is? You have to make a number of measurements of identical samples or of samples with known values. The latter is problematic. In that review they either used weighed measurements of substances as the reference or simply treated their VST as sacrosanct. And the R2 they tested sometimes differed from their reference values by as much as 0.1% TDS. For filter coffee that's not all that good.

If you had an R2 in hand you could, with some effort, use the former method. Even then you wouldn't be able to tell someone that their R2 works equally.

The review I read promised to revisit the question but with some number of R2 units. Maybe that will be revealing.

I hope this isn't off topic but what refractometer do you all use if not the R2?

I have had the Atago PAL-Coffee for years. Atago Pal Coffee vs pocket barista?

However, that was a long time ago and mine is a different version than what is sold today. VST also sold a different refractometer back then. I have no idea what to buy today, and I will say that I think that it is chicken-before-the-egg to buy any tool as expensive as any of these refractometers until you are very comfortable with your blind cupping skills, and reasonably comfortable with your sensory analysis skills. Just my opinion.

I know some people on the Kaffelogic unofficial forum who are happy with it and Christopher Feran has an Instagram post about it. The company is releasing a colour meter and grind distribution device as well.
https://www.instagram.com/p/CotWDoTMyRS ... BiNWFlZA==

There is also more data on testing here multiple R2 units and multiple original difluids: https://rmckeon.medium.com/difluid-refr ... ba8d9c9dee

There is also some info on how they find the ground truth measurements using moisture balances and also an Atago RX-5000i which is a bench top refractometer, there is probably more info but I don't feel the need to trawl through it all to find it.

As far as the R2 goes we have had no real issues with the 5 we have in comparison to both a VST and atago (anecdotally the atago had the furthest away values for us).

I don't think many home users have a need for a refractometer and both the VST and atago are far too expensive to be a recommendable purchase.