Cracks on old paintings such as the Mona Lisa look unsightly but may actually be the key to keeping masterpieces stable over centuries, according to new research.
It found restorers should be wary of filling in the cracks, as the network of fractures prevents further damage to the artwork.
The network of cracks allows the surface to expand and contract without paint peeling off and offers protection against degradation.
The crazed surface of oil paintings placed on wooden panels offers greater resistance to changes to moisture in the air than other canvases.
The Mona Lisa by Leonardo da Vinci is painted on a poplar panel and has a highly cracked surface, known as craquelure in art restoration.
A team from the Polish Academy of Sciences, University of Strasbourg and Yale University investigated cracks on the layer applied to a wood panel as a base.
This so-called gesso is a mixture of animal glue and white pigment. When wood expands due to increasing humidity, or when it shrinks when the air becomes dry, the gesso becomes cracked.
Researchers prepared wooden panels and joined them joined with gessoes prepared according to traditional recipes. The specimens were stored at 25°C and relative humidity of 30, 50, 75 and 90% for two weeks before being subjected to splitting tests, which measure how resistant gessoes are to cracking.
Using data gathered from scanning historic samples of panel paintings, the authors created a computer model of a panel painting to simulate further crack formation.
The authors found that the stress on the gesso decreased as the number of cracks increased over time, Daily Mail reported.