Cool 20 °C
Room 23 °C
Warm 27 °C
usual window
▬ sweet
▬ tart
shaded: the balanced-tart window
Day
7
Sweet
0%
Tart
0%
An illustrative model: one "effective day" at 23 °C, with speed roughly doubling for every 6 °C of warmth. Percentages show how far the batch has travelled from sweet tea to sharp, not measured sugar.