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Cupping TDS and Ext % change over time ? ?

We often host classes here at Torch.

One of the many classes we host is the Q Grader course. One of the goals of the Q course is to calibrate cuppers to a sensory standard, so when anyone in the industry talks about coffee quality we have a standard to base our decisions off of.


I also noticed throughout the 10 Q courses I have gotten to help with that many people have pre-conceived notions about how to break, clean, and pour water. 

This got me thinking, do these variables really effect TDS and extraction that much? If they do, then the Q course also needs to calibrate on breaking, cleaning, and pouring methods as well.


So I took to the cupping lab and VST refractometer to do some research.

Check out my results Below.

*Note, each experiment was done with the same coffee on the same day, at the same time. However, the coffee for each experiment was different.

So TDS results should be compared to other tests of the same type, not across. I used 11 grams of coffee and filled each cup to the top, which is 200g of water.

Extraction % = (TDS  x Beverage Weight) / Dose

In cupping, dose and beverage weight are the same, so extraction is based on TDS. I didn’t do extraction calculations, but by the nature of the formula and cupping, extraction increases as TDS increases.


One Question I am answering:

  • Do pouring methods, breaking methods, or cleaning methods effect TDS and extraction percentage?

If so, then we need to be more careful about our pouring order, breaking order, etc and calibrate.

Four different tests, each broken down into different experiments

  • Each experiment TDS will be taken every 30 seconds until 12 minutes

    • Break time

      • Will be broken at the following times and then immediately cleaned.

      • Break method will be push x2 then stir

        • 3:00

        • 4:00

        • 5:00

      • Break at 6:00

    • Cleaning Times

      • Break method will be push x2 then stir at 4:00

      • Will be cleaned at the following times

        • immediately cleaned.

        • +2 minutes

        • + 5 minutes

    • Break Turbulence

      • Break at 4:00

      • Differing breaking methods

        • Stir x1

        • Stir x3

        • stir x7

        • Push X 2, then Stir

        • Push X 7

    • Pouring turbulence

      1. Bunch of spins

      2. One steady place- low 

      3. One steady place- high

      4. Break at 4:00

      5. Use Push x 2 then stir

      6. Then test TDS every 30 seconds


      7. The “high” cups had the most bubbles on top and the lowest TDS

      8. Low and spins were very similar TDS

      9. Cup 1 of the “low” I accidentally splashed some of the coffee out of the cup, so the TDS readings were all low. 


  • Similar to what I have witnessed in French press brewing, the TDS of full immersion methods plateaus at a certain point and very slowly increases after that. With cupping, it is the same.

  • Breaking methods do not seem to matter, as long as all of the coffee grounds stay in the cup.

  • Breaking time seems to only have an effect for the first few minutes, then the TDS evens out.

  • Cleaning times do not seem to have an effect.

  • Pouring high produced lower TDS and extraction. I believe this is due to the formation of air bubbles that effected extraction. Pouring in circles didn’t seem to matter. Conceivably due to the grounds then immersing for 4 minutes before breaking.

Cupping TDS Forms