One of the difficulties with oil paints, especially old oil paints is that they don't last forever. They crack and even chip off. Sometimes, when they do, startling discoveries are made. That was the case with the privately owned Madonna della Minerva, a Madonna and Child done on a wooden panel about 1300. Records showed that the figures had been repainted as early as the 1400s with the gold leaf background restored sometime in the 1500s and then the whole thing repainted in oils sometime in the 1600s. As one might guess, by 1993, it was starting to need repainting again. It was then art archivists got hold of it and began to peel their way down through the centuries of grime and multiple layers of paint to what they discovered was, in fact, a fresco,--a thin layer of plaster into which pigment had been embedded.
Fascinated, the owner ordered it restored, only to find yet another surprise. It was by Giotto! Further research revealed it was painted originally for the altar of the Altieri Chapel in Santa Maria sopra Minerva (a church in Rome). The work has a genuinely Byzantine-Medieval appearance, yet the three-dimensionality of the figures clearly mark it as having come from the brush of Giotto during one of his frequent sojourns to Rome in the years shortly after finishing the Assisi frescos. Giotto is known to have been to Rome several times during the pontificate of Boniface VIII (1294-1303), not so much to paint but to study painting, especially the work of the ancient Roman artists, particular that of Pietro Cavallini. This painting is thought to be one of only two or three surviving works of Giotto from this period.
The Roman art Giotto went to study, included the huge Navicella mosaic which at one time adorned the wall over the atrium side of the main entrance to the original St. Peter's basilica. This modest-sized church was ordered built by Constantine, the first Christian Roman emperor, in 315 CE Finished in the year 350, it was situated over the tomb of St. Peter. The present St. Peter's Cathedral was literally built over and around it. The old brick and mortar edifice was not completely torn down until the present structure was well underway. It is believed that some of Giotto's work (along with dozens of other Medieval paintings and mosaics) were destroyed in the process. Of Giotto's work, only a triptych altarpiece and less than five square feet of the Navicella mosaic (by an unknown Byzantine artist) were saved from old St. Peter's.