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Using Refractometer with Londinium R

Hi,

I have Londinium R and using the Kafatek Flat grinder.

I've bought recently a Refractometer (Atago, and I also use the VST filters) and have started measuring my espresso extractions.

I use commercial beans (blends and SOs) from Verve / Onyx / 49th Parallel / Square Mile / Blue Bottle. These folks have provided me their recipes (dose in / espresso out / time ranges). But I am not able to get good extraction numbers on the refractometer with their recipes and my equipment. I am most often on 23%+ on Ext % (in the VST iphone App - Espresso) and cannot easily drop the TDS. I've tried to make changes to their recipe but I have not being able to have a great result. Espresso tastes ok, sometimes great. I could ignore the refractometer and just purely go on taste but I want to try to correlate these.

I have seen in various blogs / forums that people have done various refractometer experiments but I have not being able to get a clear picture of how to massage the whole setup (machine, grinder, recipe) to align closer with the refractometer / VST App readings.

Is there a rough "IF-THIS-DO-THAT" approach (for bringing the blue circle & red circle closer in the VST app chart) that people follow?

Thank you so much for your help!

Best,

Nikos.

Comments

  • Nick Kavantzas post=13999 wrote: I am most often on 23%+ on Ext % (in the VST iphone App - Espresso) and cannot easily drop the TDS.

    You bought the Atago which is not designed to work with the real VST refractometer app.

    A while ago I spent a day with a friend to calibrate a great number of measurements between the two devices on a range of identical coffee samples and my friend who is a number cruncher had the software to correlate and come up with the non-linear conversion from that specifioc Atago to my specific VST refractometer. . We discussed it with Vince from VST and even though he found the job well done, we all agreed that publishing this conversion would be a copyright issue, since it was derivative of the VST product and it would enable people to use an Atago and the VST app to get similar results. Not exactly identical results by the way because the VST device is much more precise and stable (which explains part of the price difference as well --- what you pay is what you get).
    Nick Kavantzas post=13999 wrote: Espresso tastes ok, sometimes great. I could ignore the refractometer and just purely go on taste but I want to try to correlate these.

    You are doing just that which is fine and if you find that in your combination of grinds, dose, tamp, filter basket, timing, pressure and brew weight/ratio you get your best result, you can use that extraction percentage with another bean as a local rule of thumb. Try an under-extracted ristretto and see how you like that, compare that with a long pre-infusion large volume shot and see how that measures, etc.

    Rather than using the device and app as an instrument to play darts "getting the dot in the middle" I advise you to taste, evaluate and gradually begin to understand the process. When you buy into that lab equipment (and also opting for a cheap replacement) you simply have to get familiar with it. A number is not a taste, and 20% is not necessarily the best number for this one specific bean. You have to remember that that 'target' number was the result of a large stack of results averaged.

    When I started off with my refractometry, two expert baristas in a hugely popular (always packed) specialty coffee place told me that right then their recipe had 16.5% extraction (light roasted African, EK43, updosed, extracted short on the Spirit) and since that was fantastic they kept that recipe for that batch.

    Change the assumed moisture of the bean a tiny bit and see the changed outcome of the calculation. Think again, go over notes, etc

    But by all means keep enjoying a great cup of coffee without spoiling the fun by not 'getting' the numbers.
  • Hi Frans,

    Thanks for you reply. Its good to know that the Atago and the VST App are not working well together. I'll get the VST refractometer and continue my experiments.

    I have being looking in the HomeBarista forum that you started back in 2014 (https://www.home-barista.com/knockbox/vst-refractometer-t29505.html) and have found many interesting comments from users that are useful to understand the ways to progress in a methodological way in the experimentations.

    For example, from MWJB in response to another comment:
    " bryantruitt wrote: Longer flow will increase your extraction yield. The % TDS will go down.
    MWJB: %TDS may well drop, but probably not by much as those next 2g of beverage, all things being equal, will still be carrying some TDS mass. Depends on what the flow through the bed is doing between 25g & 27g."

    This is useful to build an "IF-THIS-DO-THAT" approach. This does not mean that will give necessarily better coffee in the taste but still gives a way to navigate in an organized way and explore.

    So, I was wondering if you or anyone else has consolidated these/related type comments/thoughts into a single approach and you could share it.

    Best,

    Nikos
  • It is really simple. Sample handling: mix well, take small sample, filter and cool in a separate cup, take a few drops with pipette, drop them on the glass, wait to balance temps, measure 1-3 times.

    Extraction: imagine you're chewing the licorice wood. When you don't chew, not much taste comes off unless you suck for ages. When you chew well and then suck, a lovely rich licorice syrup is extracted in your mouth but the harder you chew and suck, the thinner the taste gets and eventually you extract wood taste, not good. Cofee is much like that.

    Grind too fine, extract too much: lots of extraction in way too much water, less optimal taste. Grind too coarse, extract very little: often, and underextraction masked by some mouthfeel. Etcetera. There is no 'logic tree' needed, just making coffee, thinking about what you just did and understanding it better as you go.

    I read on an Australian bicyclist forum in a thread about Dutch bicycles and the special techniques of breaking. I laughed silly, because in Holland I know no one who has ever talked about when exactly to use which brakes while curving a corner. We ride bicycles and wonder why tourists wobble all over the place on their rented bikes here in Amsterdam ;-) It just needs more practice.
  • Matt Perger has a lot to say about refractometry and espresso, including his step-by-step method of combining the two. Start here and follow the thread: https://baristahustle.com/blogs/barista-hustle/vst-wtf-part-1
  • Yes, I have being reading MattB's blog entries (including the refractometer ones). MattB has shared a lot of his great coffee knowledge with the community.
  • If after reading all that material you feel there is something missing, you could also write a more detailed blog / report about what you have done so far, weights in / out, flow rates measured with the Acaia, taste results, refractometer results over a few dozen shots using different beans, also measuring the roast degree of the beans so we have some idea of what type of roast you are using. Illustrations and if possible some videos of what you do and how you do it. If an extraction comes out too fast because distribution of the grinds was not done right for instance, that influences the extraction outcome.
    I blogged about it on occasion, sharing pictures, data, results, and sharing such info has taught me much, also generating helpful feedback from others.
    Merely reporting "I get 23%" does not communicate much and then there is not much feedback to provide.
    Just like reading answers to math problems does not teach you math, getting a grasp of the material needs practice and thinking done by the students themselves.
  • Nick Kavantzas post=13999 wrote: I am not able to get good extraction numbers on the refractometer (...)

    Espresso tastes ok, sometimes great. .

    One valuable quote from the article linked above:
    let's please stop acting as if we have the ultimate brew because our yield numbers say it is right. Let's use our palates, and senses
  • OK, but refreactometers have their uses. After setting up my new Kafatek Monolith Flat , I found with my Atago (unfiltered samples) that I was getting more EY variation than I expected. Denis suggested that my puck preparation technique might be the cause. I found ways to become more proficient at that and seem to have succeeded. I now get high and regular EY extractions, although for taste reasons I sometimes dial in less than the highest EY; but I certainly value the regularity. I don't know if I could have identified and worked to resolve the problem of my sub-optimum puck preparation without a refractometer.

    Matt
  • Matthew Hoffman post=14028 wrote: OK, but refreactometers have their uses. After setting up my new Kafatek Monolith Flat , I found with my Atago (unfiltered samples) that I was getting more EY variation than I expected. Denis suggested that my puck preparation technique might be the cause. I found ways to become more proficient at that and seem to have succeeded. I now get high and regular EY extractions, although for taste reasons I sometimes dial in less than the highest EY; but I certainly value the regularity. I don't know if I could have identified and worked to resolve the problem of my sub-optimum puck preparation without a refractometer.

    Matt

    Hello Matthew,

    Do you mind sharing what your puck prep is now and how you improved it from before?

    Thanks
  • I sent this reply to someone who DM'd me with the same inquiry:

    I got inconsistent results. I cured the problem by doing WDT as in this video:



    Then levelling with the OCD:



    And, finally, tamping with the LevTamp:

    https://www.kafatek.com/index.php/levtamp-auto-leveling-espresso-tamper/

    Matt

    PS I took delivery of a Londinium distribution whisk a couple of days ago. It makes a fluffier puck than does the stylus I had been using. Concerning taste, it's too early to say much, but I think the flavours may be brighter and better separated.
  • Matthew Hoffman post=14127 wrote: I sent this reply to someone who DM'd me with the same inquiry:

    I got inconsistent results. I cured the problem by doing WDT as in this video:


    Then levelling with the OCD:


    And, finally, tamping with the LevTamp:


    Matt

    PS I took delivery of a Londinium distribution whisk a couple of days ago. It makes a fluffier puck than does the stylus I had been using. Concerning taste, it's too early to say much, but I think the flavours may be brighter and better separated.

    Thanks for the tips Matt. I have looked at those Kafatek tampers, they look nice. I should be receiving my Londinium dist tool soon.

    Cheers,
    Roger
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