Coloration changes of powdered purple stained material in acid and alkaline phases at normal room temperature (about 20°C). The three images show, from left to right, the resultant pinkish appearance after standing in acid phase for 10 days, a purplish appearance after standing in alkaline phase for 10 days, and a whitish appearance after standing in alkaline phase for 18 days. The pinkish and purplish states are reversible by increasing the alkalinity and acidity, respectively. The change of purplish appearance in the alkaline phase (center) to the whitish phase (right) is not reversible. The whitish appearance persists irrespective of changes to acid phase and back to alkaline phase.