Renaissance master Leonardo da Vinci avoided the palette and mixed colours directly on the canvas, Italian researchers said after they reconstructed his work step by step "as if watching him while he painted".Using a scientific device to analyse da Vinci's Madonna of the Yarnwinder painting, researchers at the University of Florence said they were able to pinpoint virtually every stroke made by the famous Italian artist on the oil masterpiece.Researcher Cecilia Frosinini said the device showed that da Vinci avoided mixing colours on a painter's palette like his contemporaries did.Instead, he applied thin layers of paint directly onto the canvas in different colours, one on top of the other, to create a rich texture."That Leonardo used the 'velature' technique is already known, he himself wrote that in a treaty, but for the first time we have managed to reconstruct his work step by step, like as if watching him while he painted," she said."We have been able to understand what type of painting materials he used, how many layers of colours were applied and in what thickness and sequence."The painting scrutinised belongs to a collection in New York that has been dubbed the 'Ex-Reford' version, the researchers said.It is the only one of several versions of the image credited to the artist himself.The researchers used a so-called 'nuclear accelerator' device that launches particles at high speed to decipher the painting technique used by the artist.Da Vinci is considered among the greatest painters of all time, renowned among other things for his Mona Lisa and The Last Supper masterpieces, which are among the most imitated and reproduced paintings in history.