So, as I understand it the problem with the Mona Lisa in the Louvre is that layers of paints have already been stripped and damaged (the layering of very thin c

So, as I understand it the problem with the Mona Lisa in the Louvre is that layers of paints have already been stripped and damaged (the layering of very thin coats of paint is the signature of Leonardo's technique) and the varnish itself has been carefully applied by Leonardo and is somewhat part of the painting. Add that the wood panels it's on have contorted and you've got an extremely difficult piece to restore. It's better to act very conservatively with it.