Extract Mojo, and Refractometer

This is our understanding of the Extract Mojo and Refractometer, and how we’ve been using it for the results we have.

Posting this is mostly a hope to start conversation about how to best use the mojo, point out the flaws in our system, and hopefully point out some things we’ve noticed that may help, though in our short experience that’s not likely.


Brew coffee.

Stir Coffee with syringe or eye dropper (supplied with Mojo)

Take 15mL sample and place into clean/dry cupping glass (glass 1)

Stir by moving glass (dissipate heat faster)

Wait 2 minutes then place 3mL +/- into Refractometer.

Press read in Native mode.

Copy Temp. and Refractive Index possibly look at TDS

Place into Mojo, and copy results into moleskin.

Rinse syringe with distilled water (glass 2)

Dump out cup 1 and wipe dry with microfiber towel.

Rinse Refractometer with distilled water.

Wipe Refractometer lens with super microfiber from eye glasses store. (spec optical)

Repeat. allowing time for the meter to cool, notes to be taken and coffee to be prepped/conversation to be had about next experiment.


3 Responses to “Extract Mojo, and Refractometer”

  1. scottlucey Says:

    sheesh, sorry nobody’s replied. perhaps you’re spot on and need no speaking to!
    1) i’ve never tried cleaning w/ microfiber… i use science wipes, or kimwipes i think they’re called… sanitary disposable.
    2) you should get a hold of vince fedele from vst – he’ll answer any questions and explain so much behind the mojo. feel free to email me more if you can’t find his contact info.
    3) if measuring brewed coffee, i’m mainly using tds mode. vince confirmed that native mode was really for espressso and that native mode’s extended decimal reading isn’t that much more accurate, seeing as the software reads out to more decimal places than does the refractometer.

    as it stands now, mainly i wonder why when you take multiple readings from one sample you get different results. according to the directions, the user should take the average of about 3 to 5 readings, but there are times my tds reading is wildly different, more than .1 variance.

    great questions though – it’s largely important that if we as an industry start measuring our extraction percentages we know how to use these applications better than anything we know!


  2. I just got turned on to your blog and have been digging it so far. I’ve been super curious about the Extract Mojo and your musings on it and tests are some of the most interesting I’ve seen. I’m enjoying following along.

  3. That refractometer is pretty nice, but a bit dear. You can get a little hand-held one from Bellingham and Stanley for £40 (E-line ATC 0-18 Brix (Cat. No. 44-802)), set up a brix-to-RI chart from the data enclosed, and you’re away. Push the cover down for best results.

    For my local coffee shop I’ve calibrated brix to total solids (measured in a laboratory) for espresso. Pop that figure plus coffee weight and brew weight it into a six cell spread sheet and can get ‘total solids’ based on brix reading to +/- 3%. This then enables you to calculate extraction, brew ratio … And all for a tenth the price!

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