During most of my visits to Italy, I end up with neck cramps after craning my head backward for hours to look at faraway ceiling frescoes in churches across the country. But last week, I found myself peering directly into the eyes of fresco angels at the top of the Capella Maggiore in Florence’s famous Santa Croce Basilica.
These frescoes have been under restoration since 2005 and for the next few months small groups of people can climb the scaffolding to view the artwork up close. The frescoes were painted in the 1380s by Agnolo Gaddi, a disciple of Giotto, one of the architects of the Italian Renaissance.
I climbed up the scaffolding with Mariarosa Lanfranchi, a restorer from the Opificio delle Pietre Dure, Italy’s foremost restoration laboratory. She’s been leading the fresco restoration project.
One of the first questions she asked me is whether I suffer from vertigo, because we would be going up about 30 meters to reach the very top of the cathedral. Assured that I wouldn’t suffer a panic attack, she began her awesome tour by telling me that the last restoration of part of the church’s frescoes was in the 1930 or 40s.
Since then, air pollution has coated the art with a layer of brownish grime. Meanwhile, construction around the city has covered the artwork with little chunks of gypsum dust. The frescoes are porous, and with the city’s high humidity, the gypsum penetrated into the frescoes, giving the artwork a rather speckled look, Lanfranchi explained.
To remove the grime and gypsum, the restorers used the “Florentine method,” a combination treatment of ammonium carbonate, followed by a treatment of barium hydroxide, Lanfranchi said. The first step of adding the ammonium carbonate dissolves the unwelcome dust and gypsum (calcium sulfate dihydrate) so that both can be removed from the surface and inside the fresco’s pores.
But this first step of the cleaning process also has a downside. It produces some ammonium sulfate, a salt that could be problematic to the frescoes in the future. So the second step of the Florentine method is to add barium hydroxide which turns the problematic ammonium sulfate salt into barium sulfate, which is benign to the artwork. The second step also produces some barium carbonate, which acts as a stabilizing agent (called a consolidant) to the sensitive frescoes.
With more than 800 meters squared of fresco surface to restore, Lanfranchi said the scaffolding became like “a second home” to her over the past years. As we walked around the scaffolding she pointed out small details in the frescoes–a bird or an angel or a crack–with the same familiarity as someone introducing you to the charms and quirks of her own home.
She said that on a good day it was possible to treat between 1-2 meters squared of fresco. Besides the ammonium carbonate and barium hydroxide clean-up method, the restorers were also doing a pre and post treatment of deionized water. They also filled in some of the cracks with plaster and did retouching when they knew the exact color of the missing area. It boggles the mind–or at least mine–how delicate and slow-going restoration work is.
While we were touring the scaffolding, we ran into some MOLAB researchers working on an as yet un-restored area of the cathedral’s frescoes. I’ve written before about MOLAB, the roaming troupe of scientists who drive around Europe providing scientific support to museums, galleries and churches.
The MOLAB folks were using a technology called FTIR (Fourier transform infrared spectroscopy) to figure out—without taking a sample, just by shining light at the art– what the last restorers had put on this part of the frescoes as a “fixative.”
As the name might suggest, a fixative is a translucent barrier added in the past to protect the frescoes from polluted air around. Fixatives are declining in popularity, because the restoration field is increasingly taking a minimalist approach when working with masterpieces.The fixative from the last restoration was probably based on protein (say from egg), a lipid (oily extracts from plants or animal fat), a resin (from trees) or some combination of all three, Lanfranchi said. Knowing precisely which fixative was added will help restorers find the best way to remove it as a first step of the clean-up process. There’s just 80 meters squared of frescoes left to restore—and that’s exactly what’s next on Lanfranchi’s team’s to-do list.
If you want to go up on the scaffolding, you must request a tour here. Or if a trip to Florence is not in your immediate future, check out the restoration project’s amazing website for a bounty of awesome photos.
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