How To Clean a Painting
When a professional cleans an old painting he begins with a small test area on the periphery of the picture, trying various solvents to determine what works best. He starts with cotton swabs, barely dampened in distilled water. He might wet the swab with his mouth as saliva contains enzymes that are often effective at removing dirt and oils. Some cleaners use pellets of fresh bread. This process of experiment on a tiny spot on the edge of the work is called “opening a window.”
I’m learning all this from THE LOST PAINTING: The Quest for a Caravaggio Masterpiece (2005), by Jonathan Harr. I’ve come to the part where an art restorer at the National Gallery of Ireland is cleaning a picture as a favor for some Jesuit priests in the neighborhood. It is called The Taking of Christ and was purportedly painted by a second-rate Flemish painter named Hornthorst.
The restorer suspects that the painting could actually be a Caravaggio. But that is most unlikely so he and the others at the National Gallery decide to say nothing about their theory while they research its provenance.
Meanwhile back in the palazzo a Roman art history grad student has been tracing a lost Caravaggio. Some 200 years ago a sloppy record keeper working for a wealthy Italian family recorded the sale to a Scotsman of a painting by Gerard Hornthorst hitherto unmentioned in the family’s records. The Caravaggio disappeared from family records at about the same time. Could this clerk have made an error? Could the Hornthorst really be the Caravaggio?