IR reflectography is a highly valuable aid in all conservation phases.

Before a restoration because it greatly helps in assessing the conservation state. But also during the restoration itself, after the outer varnish layers have been thinned and/or retouching has been removed, since IR light will be able to penetrate to a deeper extend into the paint layer and reflectography will reveal more details, which could be hidden at first.

With reflectography, the underdrawing may become visible, as well as the various paint layers applied by the same artist (pentimenti), by a later painter, or by a restorer (inpaintings and retouching). These features, which are hidden to the naked eye, may be clearly imaged.

This is particularly useful to reconstruct the painting history and contributes decisively to its attribution.

The study of the underdrawing is particularly useful to understand the subsequent execution phases and the artist’s style.

We can understand which techniques have been used to compose the artwork, to which extend the artist knew the rules to render perspective, how he/she executed the preparatory sketch, if the artist started the composition with a free hand drawing or the sketch was originally composed somewhere else and transferred later on the ground surface etc, and moreover if it was executed with charcoal, chalk, pencil, or paint and brush.

Since painting materials show different behaviours in the near IR band, with IR imaging it is also possible to a certain extend to identify some of them.
This is what is currently done with the false-colour method, whose result is an image where the visible colors are substituted in combination with IR results.
The new digital devices dramatically improve on what was achievable in this respect with IR films.