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The Data

Below you find links till the data behind this project for S-airlock with 4-5ml water and with a tiny equalization hole in S-airlock + the cap on to lower evaporation. It is based on various sensors, e.g. sound, infrared and MPU6050, and various S-airlocks, but the volume in S-airlock have been between 4-5ml.

First of all, graph 1 shows all the hydrometer measument expressed as rG (OG-SG) during the years looking into this project. It shows you cannot just use one polynomial as mainly the headspace and fermenter shape/material do impact on bubbling rate and hence the needed “Sum blops/L” vs. rG fluctuate to much from brew till brew.

Deep diving further into the data for S-airlock in below table, you will notice the “One hydrometer reading” approach during the main fermentation at preferably around 33-66% complete, e.g. after high kreuzen, we get a error of mean of around 3 SG units meaning we can foresee the final gravity within 3 gravity points. Secondly, it should be noticed the R2 value for the various brews is close to 1.0 indicating high linearity till 1. degree polynomial. Hence, the release of bubbles is a 1. order polynomial. But this polynomial is impacted by mainly headspace and material of the fermenter.


  • rG, is the hydrometer reading at the end of brewing (final gravity, FG) expressed as the reduction in gravity.
  • rG_corr, is the calculated “reduction in gravity” based on the polynomial in use and the “sum Blops/L” at the end of brewing.
  • Error_corr, is then the difference between rG – rG_corrr at the end of brewing, and hence, express the error of mean till real life hydrometer measuments.


Above table shows all brews/data during the last years. If using the “one hydrometer reading” preferably at 33-66% (e.g. high kreuzen has just passed) into the fermentation an error of mean around 3 SG units is justified meaning we can foresee the final gravity within 3 gravity points.

All data is done with S-airlock (assuming 4-5 different types used during the testning, but all mat/soft plastic), 4-5 ml water in airlock, and the data is a mix of sensors, e.g. sound, infrared and MPU6050. For S-airlock a tiny hole in top of airlock have been drilled to equalize pressure, secondly, the “hat” was on to lower evaporation.