I currently have an old R2 Refractometer [URL=https://i.imgur.com/71yNCKV.jpg][IMG]https://i.imgur.com/71yNCKV.jpg[/IMG][/URL] [URL=https://i.imgur.com/MnHZKJv.jpg][IMG]https://i.imgur.com/MnHZKJv.jpg[/IMG][/URL] Its very time consuming to use: 1) clean the glass 2) bring unit and glass to room temperature (within a specified range) 3) ditto for the distilled water 4) calibrate the unit, 5) setup the extraction syringe and its filter 6) take the sample 7) express the sample into a mini beaker 8) dilute the sample to a specified ratio 9) bring the diluted sample to a specified temperature, within a narrow range 10) ensure that the R2 glass and the sample are at the same temperature 11) place a drop of the sample on the R3 glass 12) run the test, 13) repeat test multiple times 14) calculate average result 15) enter data into EY calculator 16) note the result That is just too much faff to be bothered. Is there an easier way, perhaps with a different unit?

The VST Lab II & III zero quickly and have better accuracy, precision and temperature compensation, they also produce a reading in a few seconds (compared to the rolling display of, say, the Atago, never used the Reichert, from before my time). Why are you diluting the sample? (Step 8). This seems faffy & a possible margin for error? But all will need zeroing, syringe filtering and 30s or so to let the expressed syringed sample cool, then again to equalise on the lens. It sounds like the main basic procedure is what you have a bugbear with. So the later models are a little bit less faff, but most of the procedure remains. I find it easy enough to measure every filter brew I make (98% of the coffee I drink) without syringe filtering, but I only occasionally do runs of measurements on non-filtered methods due to the cost of syringe filters. Noting & retaining the EY and correlating to your preference score is essential for the refractometer to give you any meaningful info.

Thanks for full reply @"MWJB"#139 . Appreciated! And found this [Refractometry Workflow](https://pocketsciencecoffee.com/2022/12/07/my-current-refractometry-workflow/) And this, from the coffee influencer superego we all know [Ultimate Coffee Refractometer Showdown](https://youtu.be/yF2fIaQS70k?si=1wyorF3xPwI8penX?t=1490su) PS Is the Reichert R2 Mini I have (which I believe was a collaboration between VST and Reichert) sufficient for my purposes? Will I gain much by buying a more recent model, or a Dilfuid R2 or ?

VST have instructions on how to take sample, https://cdn.shopify.com/s/files/1/0092/7622/files/VST_Lab_Coffee_III_USER_GUIDE.pdf?3540336393965960970 I rarely use my Atago because the workflow is slow and it's about half as precise as the VST Lab II (despite additional calibration by the vendor at purchase), which is what I consider the minimum for filter coffee, OK for espresso though. Tim Wendelboe has a video for espresso measurement here: https://www.youtube.com/watch?v=NPp0fpnH_0A For filter, I spoon about 5ml of a stirred brew into a shot glass/espresso cup, let it cool for 30-60s (whilst rinsing the just used brewer), then drop 3-4 drops onto the refractometer, allow another 30-60s to equalise and take 3-5 reads depending on how stable the reading is (half the time no variation, sometimes varies by 0.01%, sometimes by 0.02% at the most). Add to that 30-60 seconds minimum to let the distilled water equalise for zeroing prior to use (maybe while measuring out a coffee dose) and the whole process only adds about a minute to a brew. I use 3ml plastic pipettes for dropping the sample on the refractometer, these are easy to flush with 0TDS water, allow to dry out & reuse, also less prone to delivering 'bubbly' samples. The DiFluid is absurdly cheap for the spec it quotes, but I've not tried it and have too many refractometers that I don't/can't use, already. A more modern VST will be more precise a quicker to zero.

I can definitely recommend the difluid R2, the older model isn't very good but the new one is more than good enough, we have 5 of them (and I have my own one)and they all tested very similar compared to the VST that we use for QC and the atago we had. The R2 has a few quality of life features that make it nicer to use, the app is good as well but thankfully not required to use the refractometer. I like the workflow from pocket science, the temperature stabilises very well so all of the readings are close together. And having distilled water ina dropper makes it nice and fast.

> @"InfamousTuba"#p54382 they all tested very similar compared to the VST that we use for QC Interesting! Would you mind sharing the comparative results done over a sample, which can be 10-15 different coffee. It will also be good to see the standard deviations of the results. DW, if it is too much of a work. 😊

I’m wondering if my original Reichert r2 Mini (which was the result of a collaboration between Reichert and VST; it's effectively the VST I), which is accurate to 0.1 TDS, is sufficiently accurate? By comparison, the Difluid is accurate to 0.03%, as is the VST III. If my current Reichert R2 Mini is sufficiently accurate then I will just continue to use it and not throw $$ at yet another accessory. If it's not, then I would not use it. And think about what my coffee budget priorities are. FYI, with my R2, you do have to dilute the sample for espresso testing, as the unit can’t handle espresso TDS and produces an error code. But it's easy enough to make the mathematical adjustment. Any thoughts on the above @"DavecUK"#1 or @"MWJB"#139 or anyone else?

@"JHCCoffee"#p54406 You won't be able to test accuracy (so reliant on manufacturer's figs), only precision/repatability. The R2 coffee is stated as accurate to +/-0.1%TDS, +/-0.05%TDS typical. The VST Lab II is accurate to +/-0.05%TDS (precision +/-0.02%), Lab III accurate to +/-0.03%TDS, precise to +/-0.01%TDS all figures for coffee, rather than espresso. At filter strength 0.01%TDS equates to about 0.14%EY, or 0.03%TDS to around half a %EY. Precision much outside of +/-0.04%TDS starts to make things tricky over a sample of filter brews.

@"LMSC"#p54403 I can probably do that comparison in the future, might be a while until we have free time at the roastery to do it properly. The R2 had slight variance but they were consistent, so if one unit tested 0.05 TDS higher it was reliably always 0.05 TDS higher

If my math is correct, if I have a 2:1 espresso brew ratio, and a .10 (10%) TDS, the EY is .20 which is 20%. If I have a 2:1 brew ratio and a .101 (10.1%) TDS, the EY is .202 which is 20.2%. So the EY impact of .1% accuracy at a typical espresso brew ratio is only 0.2%, which is meaningless? The only thing is that I have to dilute the espresso sample by say 2:1 or I get an error code. But I can simply adjust the EY formula math for that by multiplying the resultant EY by 2.0 So my Reichert should be good enough. Am I missing something here?

@"JHCCoffee"#p54412 Your math is fine, you can multiply the TDS by the brew ratio (for espresso as it's based on beverage yield, not brew water poured). What you are maybe missing is that you seem to be confusing 'resolution' (the number output by the refractometer display) with 'accuracy' (the reading relative to a known datum, usually dehydration carried out by the manufacturer and fairly moot as far as we are concerned) and precision (the ability of the device to replicate that number when taking multiple readings of the same sample). This is the same for many devices, especially scales for instance, some are accurate to 0.1g, others read to 0.1g resolution but are only accurate to 0.4g. So, if you have an espresso that is 4x the dose weight and reads 5.05%TDS your EY is 20.2%, it could really be +/-0.2%EY if the device is +/- 0.05%TDS. No big deal, as you say. Or, +/-0.4%EY span if the reading is out by 0.10%TDS. Still useful. The higher concentration of 1:4 shots is working in your favour here, but as the concentration of the brews gets weaker for filter coffee, the precision gets worse. 1.40%TDS +/-0.05% at 1:14 (dose:beverage mass) is 18.9% to 20.3% for readings of the same sample. Repeated brews of the same coffee & method may span 2%EY or a tad over, You're going to brew multiple coffees from varyious origins which will double that span (rule of thumb), still around 4-5%EY and the target range is typically 4%EY. Still doable, enough to be of some use. It doesn't necessarily matter if your average is 19%EY or 21%EY, rather than 20%, other factors could have a bearing here. Precision is more useful for checking brew consistency. As you go farther out with the readings to say +/-0.10%TDS you now have a span of 3%EY for the same 1:14 filter sample, by the time you are considering different origins your range of readings is as wide as the likely extractions that are typically possible & much wider than the target region…not much use at all. If you are primarily concerned with espresso (especially if you can read the undiluted samples at around 1:2), this may not be of concern to you, filter generally requires better accuracy & precision.

Easier to Use Refractometer ?

MWJB

NewBoyUK Its what bean gets chucked in thats the hard part.

Subjectively, in terms of expectation (which may not be realistic) I can see this being hard. Objectively, not so much, if the output is achieved in normal time & EY

NewBoyUK I have to do roughtly 1:3 to 1:4 for unknown (cheap) beans. If they are actually labeled and have contact details on the bags (more common blends) I usually call them and generally they are 1:2 to 1:3.

I don’t see why cheap beans need a longer ratio, unless it is just to mute offensive flavours/intensity. Cheap, overly roasted beans tend to extract easily enough. Yes, many roasters suggest 1:2 to 1:3 ratios, but the bean can’t do it all by itself, some depends on whether the equipment will allow those beans to extract in those ratios. This you will be able to establish with repeated use of the 4 grinders.

You’re an engineer for the machines & grinders, not a fairy godmother for the roasting community. :-)

MWJB

MWJB The DiFluid is absurdly cheap for the spec it quotes, but I’ve not tried it and have too many refractometers that I don’t/can’t use, already.

I wouldn’t say, “I lied.”, but blame unrestrained curiosity, late night wine drinking & ‘one click’ online purchasing…DiFluid R2 arrived today. I’ll post some thoughts over the coming week…immediately, I don’t like the spoon idea - 3ml pipettes recommended.

NewBoyUK

I await your 👍👎

I believe you can share results with people so may ask for a few…… if you dont mind

MWJB

NewBoyUK I’ll post my findings here, they will be for filter brews, If satisfactory for that, espresso won’t be an issue assuming all samples are syringe filtered.

LMSC

MWJB I’ll post my findings here, they will be for filter brews,

Awesome mate! We are looking forward. :-)

MWJB

LMSC I’ve done 3 sets of 10 readings (V60 paper filtered drip, no syringe filtering of samples) with the VST LAB II and the DiFluid R2, Both zeroed at the same time & readings taken one device after the other in equivalent timeframe. I followed the VST protocol for the VST and the DiFluid protocol from their videos (the manual is not specific in this regard).

Test 1:

DiFluid average TDS after 10 reads 1.41, stdev. 0.007 (0.016 at 95% confidence).

VST Lab II average TDS after 10 reads 1.40, stdev. 0.006 (0.013 at 95% confidence).

Test 2:

DiFluid average TDS after 10 reads 1.42, stdev. 0.007 (0.016 at 95% confidence).

VST Lab II average TDS after 10 reads 1.38, stdev. 0.004 (0.010 at 95% confidence).

So far, so good, the difference in span between readings didn’t exceed 0.06%TDS, as both devices claim +/-0.03% accuracy, this seems fine…

Test 3 and the wheels seem to come off a little…

DiFluid average TDS after 10 reads 1.48, stdev. 0.008 (0.018 at 95% confidence).

VST Lab II average TDS after 10 reads 1.40, stdev. 0.007 (0.016 at 95% confidence).

So the variation in readings between devices is not a constant interval, As both are quoted as accurate to +/-0.03%TDS accuracy something seems adrift here as the difference in readings differed by up to 0.09%TDS (I, and no influencers that I am aware of, have the facility to check refractometer accuracy.) , However, the precision of the readings for both seem acceptable.

I then wondered whether the difference in protocol was causing the differences in the averages, so I repeated Test 3, using the VST protocol for both devices. So rather than plonking the hot sample onto the DiFluid lens and taking readings, I cooled the sample in an espresso cup then placed it on the lens.

Test #3 repeated with VST protocol for both devices:

DiFluid average TDS after 10 reads 1.44, stdev. 0.031 (0.069 at 95% confidence).

VST Lab II average TDS after 10 reads 1.42, stdev. 0.005 (0.012 at 95% confidence).

The DiFluid readings started at 1.50%TDS, dropping to 1.41, the VST only drifted between 1.41 to 1.42. But the DiFluid settled to 1.41. 1.41, 1.41 for readings 8, 9 & 10 (vs 1.41, 1.41 & 1.41 for the Lab II).

So I feel I have to start again, it seems logical that the plastic casing of the DiFluid may not be allowing samples to reach a steady state as quickly, compared to the steel peltier dish on the VST.

The DiFluid spoon (volume 0.65g) is a bit daft/messy. Printed instructions are scant, YT videos don’t offer any further info on taking readings,

I’m a bit disappointed that I’m having to explore a previously unmentioned test protocol seeng that this has been in the field for some months, but I’ll see what occurs over the next few days.

Data is here:

VST Lab II vs DiFuid R2

InfamousTuba

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/)

MWJB

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?

InfamousTuba

@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

MWJB

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

InfamousTuba

The whole article is a bit long winded so I did just pick out the figure, here is the full thing: https://coffeeadastra.com/2019/09/21/measuring-coffee-concentration-with-a-0-01-precision/

MWJB

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)..

InfamousTuba

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

MWJB

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.

InfamousTuba

@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

LMSC

Thx folks for the insight.

MWJB

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.

LMSC

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. 🙏🏽

MWJB

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.

LMSC

@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

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.

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