Photo n. 1 Leonardo's "Cena" S. Maria delle Grazie Church, Milan
The photo shows a small section of the "Cena" which includes the boundary line between the part recently "cleaned" by the restorer and the part still intact.
Leonardo's picture is all fractured, as we can see from the detail of this photograph.
The flakes of colour - about one millimetre large - once came off from the wall.
The restorer Mauro Pelliccioli fixed them to the wall, in 1947. The photo shows one of these flakes enlarged. In the zone n. 1 we notice the presence of the shellac, an animal resin with which Pelliccioli fixed the flakes of the whole picture.
This shellac has now been taken away by means of a solvent in the zone n. 2.
The operation of cleaning is going to be done on the whole picture.
The crown of shellac around the flakes of colour kept them from coming off from the wall.
When this kind of cleaning is completed, colour must be fixed with a new fixative.
The risk of worsening the mechanical stability of the picture consists in the specifìc hardness of the fixative they will use.
In fact, the cause of the coming off of these flakes is their hardness with regard to the hardness of the background of preparation which is in contact with the plaster.
If, owing to the application of a new fixative, these flakes should further harden, Leonardo's "Cena" will rapidly and completely scrape off.

The art magazine:  "Costume" - Anno XIII  n. 48-49 luglio-dicembre 1982