Over-cleaning old master paintings has become fashionable. The damage is irreversible.

Long past are the days that Sotheby’s and Christie’s would have an old master sale every week. But the supply is drying up. Ever more old masters enter museum collections, de facto taking them out of the art market. At the same time new buyers have entered the market, and demand has gone up.

I noticed that nowadays, un-restored and un-cleaned paintings have become rare at auctions. Supply has diminished to such extent that dirty paintings, which for decennia remained untouched in private collections, have become a rarity.

Such a pity, if alone for nostalgic reasons! Gone are the days that at an auction you could spot a masterpiece below layers of yellow varnish and dirt, and snatch it away for relatively little money because it was overlooked by the other dealers.

Nowadays, even auction houses clean paintings, if they think it will get them a better price. Fact is, the clients expect the paintings to be bright and clean.

Museums have become accustomed to restoring their masterpieces before they go to an important exhibition. Thus, the public has become accustomed to the fact that all old master paintings are always clean, even if the paintings may be 350+ years old.

The point is that even though most restorers are very professional, too many paintings are getting over-cleaned simply because dealers and art buyers alike expect the paintings to look like post cards. It’s a sign of the times and it is not limited to art; everything is supposed to look modern, fresh and above all: clean.

Strangely enough, if a Lady Di dress comes up at auction, it is considered a crime to bring it to the dry cleaners. That would destroy its aura, (and clean out any DNA that may have been left).

But what do you think will happen to the aura of an old master painting that’s being over-cleaned?

It is a restorer’s job to decide when to stop cleaning. Is any remaining age-old dirt or varnish acceptable? How “new” should the painting look? Even though, at first glance, an over-cleaned painting may look as fresh as the day it was painted, the damage to the surface is irreversible.

Basically, the surface looks like it has been sandpapered: original paint will have been lost, the paint will have an open structure that looks a bit grainy; the glazes (thin layers of paint with lots of oil, meant to build up the colour layer by layer, and to give intensity and depth to the painted surface) will have been lost. Also, even though old paint is very hard, the aggressive solvents will attack the molecular structure of the paint layer, flattening it a bit. As a result the painted surface will lose some of its depth.

Even at respectable art fairs, I see too many paintings having been treated this way. The frequency and intensity of cleaning and restoring paintings during the past few decades may prove to be more harmful than the few hundred years that preceded it.

Over-cleaning denies the history old master paintings represent and therefore robs them of their identity. But worse, over-cleaning will destroy their magic.