They brought it to Dr. Dianne Modestini, who is an expert in the conservation of Old Master paintings and is Senior Research Fellow and Conservator of the Kress Program in Paintings Conservation at New York University.
After examining the painting, Modestini began testing the most appropriate methodology to remove the overpaint. In the past, well-meaning artists and amateur restorers often “treated” paintings in a way in which the artist’s original materials and vision for the work were compromised. In an attempt to remove discoloured varnishes, too harsh solvents were often used, resulting in loss of original artist transparent glaze layers and paint. Damages to the paint layer were often heaving overpainted, even to the point of covering intact original paint.
Today, conservation is highly professional and specialised discipline, requiring years of graduate and post-graduate study and training as well as sound understanding of both materials science and art history. Conservators working in both private and public sectors adhere to strict professional Codes and Ethics that guide our practice.
Modestini recalls that as she began to remove the layers of overpaint with a solvent blend the painting began to reveal itself as something very special. The quality of the brushwork and the delicacy of the final glazes were such that she began to recognise the quality of the work underneath.
Once the layers of overpaint and discoloured varnish has been removed it was revealed that the walnut panel, originally a single piece, had split into several pieces due to a knot in the wood which as a weak point and the panel being subject to climatic stresses over its lifetime. In the past, maybe even centuries ago, the panel had been inexpertly repaired causing further damage. Monica Griesbach, a specialist in the treatment of panels, was called on to repair the panel, a delicate process that took many months.
As she was cleaning the painting Modestini noted that Christ's blessing hand was almost completely intact, while the curls of his hair, the orb and much of the drapery were in good condition. Of the face, Modestini stated,
“Fortunately, apart from the discrete losses, the flesh tones of the face retain their entire layer structure, including the final scumbles and glazes. The passages have not suffered from abrasion; if they had I wouldn’t have been able to reconstruct the losses.”
Unsurpisingly, however, the 500 year old painting did display some areas of damage to the original paint layer. The most distracting of the losses were minimally inpainted to restore the visual cohesion of da Vinci’s composition. This involved the application of paint only to the areas of loss, using the smallest of brushes. Inpainting is a delicate process that can often be very lengthy and involve complex decision-making in regards to the technique chosen.
We can choose to either simply “tone” the areas of loss in a neutral colour so that they are still visible, or we can use a technique called trattegio or rigatino where the loss is filled with several colours of paint in short brush strokes all in the same direction which at a distance the eye blends the colours and the lines. Or we can use mimetic inpainting, which Modestini used, which mimics the surrounding intact paint, all allows the viewer to appreciate the overall aesthetics of the work without being distracted by damages.
It should be mentioned that the paint used by conservators is always chemically stable and different from the original artist paint so that it remains separate from the matrix of the painting can be identified. The ethics of conservation also state that any materials or processes used are reversible and can be removed in the future.
As Modestini put it in a 2011 interview with CNN, a conservator must consider "what to touch and what to leave alone." She continued that she
“wanted [to be sure] that none of my restorations impinged on the original, that I had not done too much, because old pictures have to look old—if you take out every crack, every spot, every anomaly, they can easily look like a reproduction”.
Conservators hold a very privileged position- we get to work so closely with artworks, examining them from every angle, in different lights, over many, many hours. In doing so, you become intimately aware of the hand of the artist, their application of paint and the ways in which they have constructed their work.
One day, three years into the conservation treatment, Modestini was endeavouring to reconcile the subtle tonal transition in Christ’s damaged upper lip. She turned to a high-resolution photograph of Leonardo’s Mona Lisa and told NYU Alumni Magazine that “I suddenly realized that the Salvator Mundi couldn’t be by any painter other than Leonardo,” she continued, “I had images of the Mona Lisa hanging everywhere, and the similarities were too strong for there to be any other conclusion.”