The Ognissanti Crucifix was previously thought to have been by a relative or pupil of Giotto, but a four-year project at Italy's top restoration laboratory, the Opificio delle Pietre Dure in Florence, has convinced experts that Giotto himself is responsible for the painted cross.
"To remove the layers of grime and dust that covered the work we used water-based solvents that did not affect the tempera base of the painting," Opificio Director Marco Ciatti told Italian daily Corriere della Sera.
"The cleaning revealed a painting in an excellent state.. and of the highest quality, that leads us to question the attribution to a so-called 'relative of Giotto'," he said.
The Crucifix dates to the second decade of the 1300s and measures 453x360 cm, although a lower section at least a metre in length thought to have shown Golgotha has been lost.
Giotto would have painted the cross some 20 years after completing his famous monumental crucifix in Florence's Santa Maria Novella church.
Ciatti said the next step would be for the work to undergo an infrared reflectography exam, which will allow experts to discover preparatory drawings under the painting. The restoration of the crucifix will be presented at the end of the year.
Although renowned for his skill at life drawings at a time when stylised Byzantine art dominated, much of Giotto's life, travels and training remains shrouded in mystery.
He was born in Tuscany of a father named Bondone, studied with Cimabue, one of the greatest painters of his day, and completed his greatest masterpiece, the decoration of the Scrovegni Chapel in Padua, in around 1305.
However, the year and precise place of his birth and his family's background remain subjects of dispute, as does the order in which he completed his works and even their attribution. Photo: Giotto crucifix in Santa Maria Novella church.