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Tiny bumps rose and flaked the paint away, speck by speck. Veteran Restorer Dino Dini, 61, called in a chemist from the University of Florence named Enzo Ferroni, who discovered that the crystal growth was caused by lime, or calcium carbonate, turning into calcium sulphate. It took a year to find an ammonia solution that would turn the crystals back into calcium carbonate again. Impregnating a postcard-size sheet of Japanese rice paper with the solution and backing the paper with wood pulp, Dini and an assistant pressed each little rice-paper block for five minutes on the surface of the fresco, then repeated the procedure with a second solution. It took two years to thus cover each square inch of the vast painting.
The thousands of tiny craters were filled in with water-soluble paint—purposely duller in tone than the original hues, so that the restoration would be distinguishable to the trained eye. Exulted Dini last month, after nearly six years' work in San Marco: "Look how Fra Angelico's colors have come forth again. They are so much purer, so much more brilliant!"
Some works are beyond restoration and can only be stabilized. The most famous of these is Cimabue's 13th century Crucifix, which had been moved back to its original home in Santa Croce from the Uffizi shortly before the flood. The water took off more than 75% of its paint surface and, the restorers found, would have stripped more had Cimabue not had the nails countersunk and covered with tiny wooden plugs. Exposed, they would have corroded, ruining more paint. Until 1969, the surviving pigment was too soft to touch; then it was painstakingly removed and cleaned. Soon it will be glued back on Cimabue's original panel.
Baldini's staff has made startling discoveries as successive layers of earlier restoration and overpainting come off. Donatello's wooden carving of Mary Magdalen, which stood in the Baptistry in Florence, was described for years as an almost expressionist work. It had the blind eyeballs of old age and severe monochrome brown skin. These features turn out to be the work of later hands. On cleaning, the Magdalen's lively painted eyes, light skin and polychrome garments were restored. Thus its whole content has changed.
Three Eyes. A curiosity of this process, kept on view in the laboratories as a sort of talisman, is an 18th century Madonna which, on patch cleaning, turned out to have a 17th century version under it. When that in turn was tested, the restorers found a 13th century Madonna by the so-called "Master of the Magdalens" beneath. The final palimpsest, a Virgin with three eyes, two noses and a pair of bambini (see opposite, lower right), was playfully christened "Picasso's Madonna."