The Belvedere Palace, which dates back to 1484 and houses precious art of the Vatican Museums, is currently being re-painted with milk.
It's an ancient recipe that has proven more lasting than any modern synthetic paints: "We're not nostalgic for the past," said the Vatican's chief architect, Vitale Zanchettin.
"The point is that we think these solutions age better. They are tried and tested."
In line with Pope Francis' emphasis on ecology, the milk itself comes from the Pope's cows, raised at the papal summer residence of Castel Gandolfo, just outside of Rome. It is mixed with slaked lime and natural pigments, in this case, the original cream color used in the 1500s and hand-patted onto the walls with a centuries-old technique.
The small production of milk is branded "Ville Pontificie." Credit: CNN
Barbara Jatta, the director of the Vatican Museums, says that Pope Francis' encyclical on the environment is their guidebook for restoration work: "We really tried to apply these non-invasive methods," Jatta said, "Non-invasive for the environment and for the people."
The Vatican has been at the forefront of research on the use of essential oils to clean and protect the 570 statues and other marble works of art in its gardens.
The beauty of the Vatican Gardens' 22 hectares belies the risk its plants, trees and soil pose for the ancient sculptures placed among them. Fungi and bacteria from plants and soil slowly erode the marble works, which are already exposed to potentially damaging natural elements.
To find an environmentally friendly solution to the problem, the Vatican conducted several years of research, which they shared during at international conference in October 2017. Results showed that essences of oregano and thyme were effective in preventing the bio-deterioration of marble without damaging the artwork or the health of those who work with it. The oils are sourced from certified organic crops in Sicily.
People, not machines
Working with environmentally-friendly products is as important for the health of their employees as much as for their art. A permanent staff of 100 at the Vatican Museums continually clean and repair ancient art and buildings for the 6 million tourists who visit every year.
The cost of human labor is expensive, but the Vatican prefers to employ people rather than machines, according to Zanchettin. Restoring artwork and architecture requires detailed technical skill and years of experience that so far cannot be duplicated by a computer: "It's very manual, hands-on work, aimed at employing people rather than machines," said Zanchettin.
"It's better to pay people than machines," he added.
In a world where the computer can do most anything, at the Vatican, the hands of artisans and the bounty of mother nature still count.