Assesses the merit of Florentine methods of wall paintings conservation based on the use of mineral treatments. Discusses serious problems of sulphation, particularly the effects of gypsum, and reviews appropriate tests to monitor them. The methodology of cleaning and conservation using ammonium carbonate and barium hydroxide is outlined. Evidence is given of the first frescoes by Fra Angelico and Sogliani - treated with barium . Details photographed before conservation in 1973 and 1975 are compared with photographs taken in 1987, which demonstrate and confirm a generally satisfactory result.