A tomato ketchup-stained work by LS Lowry has been restored ahead of its public debut in Salford.
The oil painting, titled The Thames at Greenwich, is thought to have picked up the stains in a family home where it has hung since the 1970s.
A spokeswoman for The Lowry arts centre said the work "had a light layer of surface dirt [and] two small and very old, ketchup stains".
It will be on show at the centre, along with a related drawing, until December.
The two works - created between 1957 and 1959 - relate to a much larger 1959 work by the artist, called View of Deptford Power Station from Greenwich, which is part of the National Maritime Museum's collection in London.
Claire Stewart, curator of the Salford centre's Lowry collection, said the artist was "a regular visitor to London, but his views of the city are relatively rare".
"The best known are his paintings of Piccadilly Circus, which are busy with cars and pedestrians.
"His fascination with waterways, however, meant he was obviously drawn to the Thames - and these works are a great example of that."
She said the works had not been exhibited in public before and it was "very exciting to be able to display pictures which will be completely unknown to our visitors".
- Born in November 1887, Laurence Stephen Lowry lived and worked around Manchester and Salford
- After being rejected by the Manchester Municipal College of Art in 1903, he continued to take private art classes
- In 1953, he was appointed an official artist at the Coronation of Queen Elizabeth II
- In 1968, he rejected a knighthood proposed by the prime minister in the New Year's Honours list
- Lowry died on 23 February 1976, seven months before the opening of a major retrospective of his work at the Royal Academy, London
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