The gilded fresco had been hidden beneath SIX layers of paint at St.Eunan’s Cathedral in Letterkenny.
However the painting, which depicts an angel holding a banner with the words Magnificat Anima Mea Dominum, was discovered during the €700,000 restoration.
Restorers had to use CSI-style tactics to locate types of paint used in the original masterpiece which included priceless Italian gold leaf.
The painting, which dates from the 1930s, was created by renowned artist Harry Clarke in Dublin, and is located on the wall at the back of the Cathedral’s altar in an area known as Our Lady’s Altar.
Now crowds are flocking to see the finished masterpiece.
“We suspected something might be there. Over the years the gold leaf and bright colours went out of fashion and were painted over.
“It was a slow and painstaking job but it was really worth it in the end when we discovered the painting and then started to restore it,” she said.
In total it took thee months to restore the painting which Ms Bothwell believes was painted on a canvas at Harry Clarke’s studio in Dublin and then stuck onto the Cathedral Wall using rabbit-skin glue.
“In total it took three months to restore but 75% of that work was removing the six layers of paint over the painting.
“Once that was done paint analysis was carried out to discover the exact colours used in the original painting so we could reproduce those,” revealed Ms Bothwell.
Included among the new materials was a consignment of 23 (and three quarter) ct gold Italian paint.
Conservator Ms Bothwell said she was only happy to be able to preserve the works of historic artists such as Harry Clarke.
Fr Eamonn Kelly, of St Eunan’s Cathedral said “It looked lovely and we didn’t know if it had been destroyed or not.
“We are delighted that it has been uncovered and it really adds to what has been a beautiful restoration,” he said.