Four micro-samples taken from existing fissures were analysed by optical, electron and scanning microscopy.

Optical microscopy is a basic technique for viewing materials that grants access to various superimposed strata of paint (of which only the outer is visible by the unaided eye), and note their colour, texture and shape. Electron microscopy allows greater magnification and hence the obtainment of more precise results, as well as an elementary chemical analysis of pigments.

The specimens analysed reveal colourful strata in the inner layers of paint that form a sharp contrast with the outer blue monochrome, proving that the painting was completed in several stages characterised by notable chromatic variations.

When Picasso painted Barcelona Rooftops the underlying layer of paint was dry, which confirms that a certain amount of time elapsed between the execution of the two compositions, during which time his palette underwent a radical change.

Barcelona Rooftops - Pablo Picasso

Map of the localisation of the samples

Sample area 1 Sample area 2 Sample area 3 Sample area 4