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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. 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.

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.