This paper presents some of the most relevant results of an ongoing study on the penetration behaviour of adhesives using fluorescent labelling which was initiated in 2004 at the Stuttgart State Academy of Art and Design. It shows the penetration of gelatine, methyl cellulose (Benecel A4C), and poly(iso-butyl methacrylate) (Degalan PQ611, formerly known as Plexigum PQ611, equivalent to Acryloid B-67) during re-adhesion of flaking paint on canvas. Fluorescent labelling before application allows an exact localization of adhesives and provides both a better understanding of the penetration process and an opportunity to optimize consolidation treatments. Our experiments visualized the above-mentioned adhesives in the case of flaking paint layers, which allowed to optimize the forms of application in order to create the required adhesive layer between the flaking paint layer and the canvas. First, the labelling procedure, the equipment, the specially developed test samples, and the detection methods are explained. Subsequently, the differences in the penetration behaviour of gelatine, methyl cellulose, and a mixture of both are demonstrated. Finally, the penetration and migration processes after an application of Degalan PQ611 during the re-adhesion of flaking paint from the front and through the back of the canvas fabric are discussed.