A blue-gold painting measuring 125 by 89 centimeters is tilted on a wooden easel. Lucida, a 3D scanner from Madrid, stands in front of the painting. The colossus consists of horizontal rails of about one and a half meters on which a long, vertical bar of metal moves very slowly back and forth. Hanging from that beam is a construction of two small cameras and a laser.
Lucida has been standing in a small room in the basement of the Catharijneconvent in Utrecht since yesterday to make a 3D reconstruction of The Crucifixion of the Master of Lamentation at Lindau, a painting from about 1425. The scans should clarify the best method of restoration. “We are faced with a dilemma,” says restorer Caroline van der Elst. “Experts disagree on what the background color of the restored original should be.”
The painting depicts Mary, the crucified Christ and the Evangelist John. The blue background was added later, probably in the sixteenth century. “The shade is typical of the taste of the sixteenth century and in that period people also wanted to show their wealth,” says Van der Elst. The azurite, the stone from which the blue pigment is made, is very precious in its pure form. “By the way, the azurite was applied very carelessly. I have never seen this before.”
On the original from 1425, the background was gold with gold tendrils. Van der Elst: “The golden relief stood for the heavenly paradise – the flat foreground with the crucifixion and the two figures stood for the earth. If the blue had been added much later, I would definitely remove it altogether. But the azurite itself is also so old and precious that it has become part of restoration history. Difficult.” Two 3D versions will be printed for comparison: one with a full gold background and one with a polished blue background.
Tenth of a millimeter
The day before, the specialists from Madrid had already made a 2D scan of the colours. Now they make a 3D scan of the relief of the painting. “Every tenth of a millimeter Lucida sends a laser pulse onto the painting,” says Carlos Bayod, one of the specialists from Madrid. He and a colleague have been scanning the painting all day. “Due to small differences in height in the painting, the light from the laser is distorted. The two black-and-white cameras capture the distortion of the light from two angles.”
Next to Lucida, a colleague of Bayod looks at part of the gray 3D scan. “Special software automatically converts the recordings into an elevation map.” Bayod continues. “The map has X and Y coordinates and the Z coordinates (indicating elevation) are indicated in shades of gray.” Bayod briefly turns Lucida off so he can show the gray card. “If people get too close, the laser vibrates and we partly have to start over. She is really very sensitive.” Brush stripes, structure in the wood that forms the background, the artist’s highlights: all details can be seen.
When the relief scan is ready, Bayod and his colleague will combine it with the color scan. The combined scan will later be printed in 3D. “On other materials, but visually it is an exact replica,” says Bayod.
Sketches and Tombs
It is the first time that a 3D reconstruction is part of a restoration. Lucida was already developed in 2011 by the company Factum Arte and now travels the world. She scanned the sketch Epiphany from Michelangelo in The British Museum and made reconstructions of the tombs in the Egypt in Egypt Valley of the Kings. Those reconstructions are now on display in a museum. “Sometimes originals are no longer accessible to the public,” says Bayod. “That may also happen with the tombs. We will then prepare an alternative.”
It is special that four disciplines work together: museum scientists, art historians, restorers and engineers. “I visited the Catharijneconvent together with art history students and then museum curator Micha Leeflang talked about the dilemma,” says Sanne Frequin. She is an art historian at Utrecht University. “A week earlier, students received a guest lecture about 3D printing from Liselore Tissen, technical art historian. The students and I came to the conclusion that a 3D reconstruction of the gold original and of a polished variant can help in the decision.”
“I really hope that we will remove the azurite,” says Van der Elst when the rough version of the scan is later presented to a group of experts. „Back to how the artist originally intended; back to the dramatic. The streams of blood from Christ’s wounds are now probably mostly hidden under the blue.”
But the majority of those present disagreed. “According to international agreements, every step of the restoration must always be reversible. Removing the blue is not,” noted one of the experts present. “You can no longer stick the azurite that the artist applied in the sixteenth century on the painting.”
The researchers are expected to receive the funds within a year with which they can print the 3D scan. The decision about the background is then made.