Infrared light penetrates deeper into the painting's structure than visible light (move your mouse on the top of the pictures). Photographs taken by means of infrared reflectography (IR) can show underdrawings beneath the topmost design layers; fills where the original paint and ground layers are lost; structural damage such as tears and holes; and changes that the artist made in the composition.

When paintings are exposed to electromagnetic waves in the infrared band of the spectrum - which are slightly longer than those of visible light - some waves pass through the upper surface, while others are absorbed and reflected off the underlying layers.

Special infrared-sensitive cameras allow us to see differences in the absorption of infrared light upon the underlying layers, thereby revealing the initial stages of a composition. Infrared reflectography is especially valuable for studying underdrawing, or the initial laying out of a composition with charcoal or graphite. For a more detailed infrared image, we digitally capture small portions of a painting at a time. Several methods can then be used to assemble infrared images into a composite view called an infrared reflectogram.

The image below shows the final result of the restoration. Indeed by removing a nineteen century modification, the original armillary sphere is brought back to light.