By combining different dyes, however, a wide range of shades can be achieved in commercial pigments and paints. Examples include Basic Violet 11, Basic Violet 10 (rhodamine B), Basic Red 1 (rhodamine 6G), Acid Red 52, Solvent Yellow 44, Basic Yellow 40, Solvent Yellow 135, and Solvent Yellow 160:1. The number of organic dyes used to produce fluorescent pigments is quite limited. In fact, when irradiated with visible light, they give both reflected and emitted radiation as a response, leading to an apparent reflectance higher than 100%. Daylight fluorescent pigments differ due to their very bright colors from those fluorescent pigments whose emission can only be excited by UV radiation. It was thus possible to obtain fluorescent pigments with an adequate particle size, which could be used in paints similarly to traditional organic and inorganic pigments. ![]() At the end of the 1950s, a new process was patented, which made it possible to obtain pigments by combining fluorescent dyes with a new class of polymers, in particular a thermoplastic resin based on melamine–formaldehyde- p-toluene sulfonamide. ![]() In the 1940s, the Switzer brothers succeeded in obtaining “daylight” fluorescent pigments, the emission of which can also be excited with visible light. Initially, such paints required irradiation with UV light to show their unique optical properties and were prepared using white shellac colored with fluorescent dyes. In particular, the use of both fluorescent and phosphorescent pigments, alone or combined with conventional synthetic organic pigments, has been recognized.įluorescent paints were developed in the 1930s by the American brothers Robert and Joseph Switzer. In the present work, a non-invasive in-situ investigation based on Raman, fluorescence, and visible-reflectance spectroscopies was performed on a series of Black Light Art paintings exhibited in Milan (Italy) in 2017, succeeding in the identification of the materials used by the artists. The Italian Black Light Art movement exploits the possibility of conveying different aesthetical messages depending on the kind of radiation (UV or visible) with which the artwork is illuminated. The peculiar optical properties of these pigments have attracted more and more the attention of famous artists since the middle of the last century. ![]() Even the other class of luminescent pigments, namely the phosphorescent ones, is now produced industrially. Their chemical composition has been optimized to obtain the best physical properties, but is not usually disclosed by the manufacturers. Since their introduction in the early decades of the 20th century, fluorescent pigments have found progressively wider applications in several fields.
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