Pietro Paolo Cristofari

In the 18th century the Fabbrica of St Peter's, the office that ran the basilica, set about replacing the paintings on its altars with copies in mosaic, which were thought to stand up far better to time. Pietro Paolo Cristofari spent his working life on that project. He was born in Rome in 1685, the son of the mosaicist Fabio Cristofari, who died when the boy was four, and he was working for the basilica by about 1711.

His first great piece was the Navicella, Saint Peter on the Sea of Galilee, copied from a painting by Giovanni Lanfranco between 1720 and 1726. On 19 July 1727 the cardinals in charge appointed him head of all the mosaic painters working in St Peter's, a post that after him went to painters. In July 1730 he finished his copy of Guercino's huge Saint Petronilla, and copies after Domenichino, Maratta and Poussin followed. The work depended on coloured glass pastes developed in the 1710s by Alessio Mattioli, in many more shades than the old Venetian enamels. Pope Clement XII made him a knight, and he died suddenly in Rome in February 1743.