Transillumination is a non-invasive analysis used in the field of art restoration to study the internal structure of materials. In paintings on canvas, it provides information on the state of conservation of the support, the thickness of the preparatory layers and the execution technique. It consists of illuminating the work from behind with a light source, allowing to observe variations in density, thickness and transparency in the materials. This technique is particularly useful for identifying structural defects such as tears, rips, patches, thinning or gaps, providing crucial information for restoration.