So for the difluid R2 i use the provided spoon to take the sample for filter and then put it on a tablespoon to let it cool down. The R2 definitely struggles to cool down the sample compared to the VST, temperature difference between zero and sample has a big effect on TDS (data from Jonathan gagne) with room temperature being 75f in the graph below

Following the pocket science workflow gives the most consistent results and it is still usable for the VST to make sure the temperature is stable (https://pocketsciencecoffee.com/2022/12/07/my-current-refractometry-workflow/)

Coffee Roaster. Home: Sage Dual Boiler, Niche Zero, Ode v2 (SSP), 1zpresso ZP6 Work: Eagle One Prima EXP, mahlkonig e80s, Mazzer Philos and lots more

  • MWJB replied to this.

    InfamousTuba If this is DiFluid’s test protocol, they should say so somewhere?

    You’ll see from my tests there was no issue with the VST precision using their protocol. I’m not sure why Gagne would be measuring samples at such high temperatures?

      @MWJB It isn’t difluids protocol, they aren’t the best at providing good protocols and information. So it means using a different protocol which is a bit annoying instead of being able to use the same one.

      Gagnes temperature starts at his room temperature of 75f (23.9c) and goes up to 90f (32.2c) which is warm but not that hot

      Coffee Roaster. Home: Sage Dual Boiler, Niche Zero, Ode v2 (SSP), 1zpresso ZP6 Work: Eagle One Prima EXP, mahlkonig e80s, Mazzer Philos and lots more

      • MWJB replied to this.

        InfamousTuba Sorry, the chart said, “Sample temperature”, rather an ambient temperature.

          InfamousTuba It is sample (not room) temperature according to the article, but no one would do this in real life (after reading VST’s instructions)..

            No one would use those instructions, they are from quite a few years ago. It does say room temperature was 75.7f just under the figure that I copied here

            Coffee Roaster. Home: Sage Dual Boiler, Niche Zero, Ode v2 (SSP), 1zpresso ZP6 Work: Eagle One Prima EXP, mahlkonig e80s, Mazzer Philos and lots more

            • MWJB replied to this.

              InfamousTuba The instructions were written by the guy who innovated the method by which a refractomer is used to read coffee TDS, produced the first coffee refractometers & set the precision & accuracy specs. They still work.

                @MWJB That is the technique I follow with the VST but the difluid (and the atago) don’t have the same temperature correction that the VST does, VST can account automatically for temperatures between 15-40c. That is the difference between a <£200 device and a £700 device, you do get some better features and they might be worth it for some users

                Coffee Roaster. Home: Sage Dual Boiler, Niche Zero, Ode v2 (SSP), 1zpresso ZP6 Work: Eagle One Prima EXP, mahlkonig e80s, Mazzer Philos and lots more

                Thx folks for the insight.

                Three more tests now added, same protocol for both devices.

                Stir coffee sample and place a teaspoonful into an espresso cup/shot glass to cool. For all devices this sample will need syringe filtering if espresso, French press, cupping, Aeropress, or pour over made with very fine grinds (e.g. any brews with significant suspended solids, or for absolute best results for all methods).

                Calibrate with distilled water left on the lens for 1;00. Clean lens with lint free cloth/science wipe.

                Add sample to refractometer (3 drops to VST, 6 drops to DiFluid R2), wait 1:00. Now would be a good time to start tasting your brew, if cool enough,

                Start readings, I took 10 from each.

                The averaged difference in TDS between the devices was +0.03%TDS higher with the DiFluid. Which is reasonable as both claim +/-0.03%TDS accuracy..

                The stdevs in readings were:

                DiFluid R2: 0.007, 0.010, 0.005 - 0.007 averaged and 0.016%TDS extrapolated to 95% confidence level.

                VST Lab II: 0.007, 0.070, 0.070 - 0.007 averaged and 0.016%TDS extrapolated to 95% confidence level.

                So, as far as this test can tell they are equivalent with this protocol. In terms of workflow, the VST Lab is quicker to stabilise and reached the average reading in 3-5 reads (I wouldn’t be too concerned about whether the reading recorded was 0.01%TDS out). The Lab II I used has been replaced by VST for the more accurate & precise Lab III.

                This makes the DiFluid R2 quite a step up from the Atago & Amtast offerings in terms of performance. The workflow isn’t as smooth as the VST Lab series but I guess at the price difference, that’s a fair trade off. The Atago workflow is much slower due to the rolling display.

                  MWJB Exciting, extremely useful and awesome work!

                  The comparative results are very interesting.

                  Looking at your sheet, I am amazed to see the test 3 for the Peruvian coffee at room temperature / 23+C on par with each other.

                  Based on your results, this device is enough for home baristas even for filter, IMO. Of course, as you had suggested, syringe filter is recommended for the best outcome. Would that still be required even for filters like Clever (short and long steps), V60 and Hario Switch?

                  Thank you for the great piece of work. 🙏🏽

                      LMSC Whether you need to syringe paper filtered brews is more related to grind size used, so for 12% 400Kruve (probably a little finer than that too) and coarser, I wouldn’t bother. Though I have seen recommendations to brew pour over at very fine settings (like 40-45 on Niche). I wouldn’t recommend this myself, but if you were to do this, you would see significantly elevated readings, maybe by a couple of %.

                      If you were doing some kind of professional study/science then syringe filtering everything is recommended. If, on the other hand, you wanted a ‘finger in the air’ idea of extraction for Aeropress/very fine Clever/Switch steeps & very fine V60 pour over brews, you can still obviously take readings, but best to state whether syringe filters were used and take any unusually high EY readings with a pinch of salt.

                      Aeropress filters and holder have some gaps that let silt through, hence why syringing is always recommended.

                        @MWJB I have to admit your tests saves a lot of money for filter enthusiasts like self, although there is a hardly justification for not paying £700 for VST III that will certainly last a few life time. :-)

                        I am aware the filter at syringes are meant for one-time use. Do you wash in distilled and reuse ?

                        What’s your go to place for syringes and filters please? Thx

                        • MWJB replied to this.

                          Without judging the article below, there seems to some variability in DiFluid 2’s performance between devices.

                          Edit:

                          Not sure, if this is R2 Extract, though.

                          • MWJB replied to this.

                            LMSC Syringes can be flushed with distilled water, dried & re-used. The filters are single use, no I don’t re-use them. Hasbean are the UK distributors of VST products.

                              LMSC I can’t see the raw data, or sampling method details there, not sure why they tested with sucrose as only the dual scale Atago shows Brix v TDS, the other devices do not display Brix.

                              Looks a bit confused & sloppy to me.

                              Why 19 samples on the instant?

                              Why test 5x R2 but only 1 each of the others?

                              Not trying to convince you, or anyone else of the usefulness of the R2, A bigger study than my test would be better, but this doesn’t look like it.

                              • LMSC replied to this.

                                  MWJB I generally tend not to judge articles / research that fall outside my area of expertise.

                                  But, my immediate thoughts were notable variations in the outcome between DIfluid devices, yet still showing them on a positive framework, and VST apparently underperforming against home truth.

                                  The data used in research is generally not published IMO. One can contact the authors, should the data be required. Of course, I am no way affiliated to the author. 😁

                                  Your research and tests are not just invaluable to baristas but also completely transparent and unbiased. So,

                                  Giphy - Well Done Good Job GIF by Pudgy Penguins

                                  :-)

                                      LMSC and VST apparently underperforming against home truth.

                                      There is no ‘home truth’ for the sucrose test, again because sucrose is measured in the Brix scale which is not available for most of the devices shown.

                                      Neither is there ‘home truth’ for the instant coffee because they haven’t carried out any filtration & dehydration to back up the dissolved solids assertion. As I stated, early on, I am not aware of any influencers, commentators nor bloggers who are equipped to make determinations on accuracy compared to a datum/home truth. This is exactly why I avoided discussing accuracy (apart from relative averaged readings vs manufacturer’s own claims).

                                        8 months later