The painting that was cleaned

When a gallery cleaned a seventeenth-century portrait, the sky turned from brown to blue and the public complained.

The brown had never been intended. It was varnish, applied to protect the surface and to give the fashionable warm tone of a later century, and it had darkened unevenly over three hundred years. Removing it revealed what the painter had mixed. Technically the gallery had restored the work; emotionally it had taken away the painting people remembered.

Both reactions have a case. A painting is a physical object with an original state that can be investigated, and conservators can show, pigment by pigment, what was there in 1650. A painting is also an object with a history, and the varnish was part of that history for longer than the paint had been bare. Cleaning does not return a work to its origin; it chooses one moment in its life and discards the others.

This is why modern conservation prefers reversible treatments and documents every intervention. The aim is not to be certain that this generation has chosen correctly but to leave the next generation able to choose differently. A varnish that can be removed again is a decision that has not been finalised.

What cannot be undone is the loss of evidence. Once a layer is dissolved, the information it carried about later tastes, later owners and later repairs is gone. For that reason some galleries now take a small cross-section before cleaning and keep it, so that the painting the public argues about and the record of what was removed exist side by side.