The Master of Barberino and Pietro Nelli, painters active mainly in the second half of the 14th century, began to decorate the rectangular chapel around 1360.
fter a thirty-year interruption, the decoration of the chapel was resumed, as requested by Benedetto di Nerozzo degli Alberti in his will dated 1387. A The work was assigned to Spinello Aretino, a painter in great demand toward the end of the century, who frescoed the first bay with vivid new scenes from the life of the Saint, creating a cycle of eight episodes.
Starting from the lunette on the right-hand wall, the scenes are: the Conversion and the Baptism of Catherine, mparted by a hermit monk; the Mystical Marriage of the Saint with the Baby Jesus and the scene where St. Catherine refuses to worship idols at the order of Emperor Maxentius. On the opposite wall: the Dispute with the Pagan Philosopher and the Burning of the Philosophers, illustrating the martyrdom of some of Catherine’s converts to Christianity; a double scene set in prison illustrates the Conversion of Empress Faustina and of Porphyrius, military captain and Christ’s Visit to the saint. ; This is followed by Beheading of Porphyrius and the Converted Soldiers.