I used to rely on the float test exclusively. Drop a teaspoon of starter into a glass of water — if it floats, it is ready; if it sinks, wait longer. It is useful, but it is not the complete picture. A starter can be at peak activity and still sink if it has not been recently fed. And it can float when it is well past peak.

Reading a starter properly means observing the whole picture: rise height, dome shape, bubble structure, and smell. All four together tell you where in the activity cycle the starter is. The panel below maps the three main states.

An overripe starter is not dead. It still works for pancakes, flatbreads, and crackers — anything where the fermentation flavour is welcome but you do not need maximum leavening power. Feed it back to health before the next bread bake.