Edvard Munch's painting, 'The Scream', is one of the most famous works of art in history.

Despite being widely known, a mystery has surrounded the masterpiece for more than 100 years – an unknown white mark beside the distinctive figure.

While it was previously thought to be a bird dropping, researchers have now analysed the painting and discovered that the white mark is in fact wax.

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Despite being widely known, a mystery has surrounded 'The Scream' for more than 100 years – an unknown white mark beside the distinctive figure. It was previously thought to be a bird dropping, but researchers have now discovered that the mark is wax

THE SCREAM 'The Scream' is the popular name given to each of four versions of a composition, created by the Expressionist artist Edvard Munch between 1893 and 1910. The German title Munch gave these works is Der Schrei der Natur (The Scream of Nature). The works show a figure with an agonized expression against a landscape with a swirling orange sky. Edvard Munch created the four versions in various media, including paint and pastel. It is estimated that each composition is worth over £110 million. Advertisement

Edvard Munch painted four versions of 'The Scream' between 1893 and 1910, and the most famous version, which features a figure screaming, with a swirling orange sky behind, now hangs in the Norweigan National Museum.

Not only is that the most famous version, but it is also the only one with a strange white mark next to the figure.

Until now, it was thought to be droppings from a bird, as Munch often worked outside, meaning the painting would be easily accessible to nearby animals.

But researchers from the University of Antwerp have now analysed the mark to unveil the true source.

The researchers used a machine called a Macro X-ray fluorescence scanner, which can analyse the composition of materials.

The researchers used a machine called a Macro X-ray fluorescence scanner, which can analyse the composition of materials

A micro-sample of the smudge was then taken and sent to Hamburg for further analysis

This has previously been used to understand more about other works of art, including paintings by Rubens and Van Gogh.

The results from the scan immediately ruled out paint, as there were no pigments or calcium detected.

A micro-sample was then taken and sent to Hamburg for further analysis.

The results from the scan immediately ruled out paint, as there were no pigments or calcium detected

The white splatters were studied under an optical microscope (left), before the results were analysed by a computer (right)

Frederik Vanmeert, a PhD student who worked on the study, told The Mirror: 'I immediately recognised the diffraction pattern of wax as I encountered this material several times upon measuring paintings.

The researchers suggest that the white spots are splatters of molten wax that Munch accidently dripped from candle in his studio.

Dr Geert Van der Snickt, who led the study, said: 'Bird droppings can pose a significant threat for monuments, outdoor statues and brand new cars.

Frederik Vanmeert, a PhD student who worked on the study, is pictured using the macro X-ray fluorescence scanner to analyse the substance

'But I did not associate it with easel paintings, and certainly not with quintessential masterpieces that are valued over 100 million dollars.

'Solving the mystery of the bird droppings on the Scream demonstrates why our discipline has much equipment in common with forensic experts.

'Like forensics, the field of cultural heritage science is characterised by a rapid introduction of improved, state-of-the-art techniques and this allows us bringing to light completely new information on iconic works of art.'