document: The picture of Men Drinking in a Pub appears to have another work on the reverse, partly covered by wall paint.
  The piece was found during renovation of the artist's previous home in Whitworth Terrace, Spennymoor, by new owners Joe and Deborah Smith.
  Auctioneer and art expert John Anderson said it was "a piece of salvage that may yield a masterpiece".
  "Most artists, if suddenly touched by the muse will grab whatever is available to work out the inspiration," he said.
  The artist, who died last year, started working in the mines when he was 14 and became famous for his paintings of everyday life in the industrial North East after attending the Pitman's Academy.
  "In this case, presumably, he looked at it and thought 'there's a painting I'm not satisfied with'," said Mr Anderson.
  "Rather than going to the shop when he was panelling the bathroom cupboard, this was a cheap and convenient expedient."
  Mrs Smith, whose father was Cornish's cousin, said the panel was not signed but "it is definitely a Cornish because his son-in-law Michael has authenticated it and has written a letter of authentication".
  The painting is to be auctioned by Anderson and Garland in September.
  An early self-portrait of the artist with a hidden portrait of his wife on the other side was sold by the auctioneers for Â£13,500 in January.
summary: A painting by "Pitman painter" Norman Cornish has been discovered being used as a bath panel in his former home.