Paintings last longer on canvas than wood or plaster – so from the 18th century CE on, restorers have transferred famous art onto canvas using razors, laughing gas, and glue.
Art preservation is difficult. Many works of art were made on materials that fade, rot, warp, or decay. Paintings on wood panels were especially prone to these problems, so early art restorers developed some difficult, potentially destructive, but effective techniques to move paintings directly from wood or plaster to canvas.
For wood panels, the restorers began by putting paper and cloth over the picture. They then stripped back as much of the wood backing as possible with planes. When they got close to the paint, they stripped back the rest of the wood with razors. When they got closer still they applied solvents and chemical treatments (including, it is thought, nitrous oxide) to remove the last of the backing. What was left was essentially just the paint, sitting upside down on paper.
Once you’d finished, all you need to do is glue the paint back onto canvas, and the transfer is complete. Many paintings by Leonardo Da Vinci’s workshop suffered this treatment (the Lansdowne Madonna, for example), and it may have been used on Botticelli’s Pallas and the Centaur as well.
The most famous transfer of this kind has to be the Black Paintings by Francisco Goya. Towards the end of his life Goya painted the inside walls of his home with fourteen paintings of such haunting beauty (or haunting eeriness) that they have resonated with artists and art-lovers ever since. He never intended for anyone else to see them – they were painted on wallpaper and not easily moved.
Fifty-one years after Goya left the house (and 46 years after his death) the paintings were carefully stripped off the walls and pasted onto canvas. You can see them now in the Museo del Prado: Saturn Devouring His Son (pictured above), The Dog (my favourite), and Witches’ Sabbath (also known as The Great He-Goat).