# Spectral Raman Database of Modern Acrylic Paints at 532 nm and 633 nm Laser Excitation Wavelengths
## 1 Introduction  
The use of acrylics in the artistic field dates back to the early 1950s. They were met with great enthusiasm by artists of the time. [PERSON], a prominent American painter active in the 1960s, stated the following:  
_I changed to acrylics for a number of reasons. Once, I was told that they dry faster, which they do, and that they retain their original color, which they do. I would say durability and light and the fact that one can use water instead of turpentine: all that makes it easier given the abstract image... As painting needed less and less drying time, depth, and so forth, the materials came along that made that more obvious_[1, 2]. Today, as in the past, acrylic paints remain widely used in artworks due to their ease of application, ability to adhere directly to various supports and rapid drying. Furthermore, once dried, the paint becomes insoluble, allowing for layer superposition without reactivating the underlying paint [3]. Acrylic polymers are characterized by an optimal combination of chemical and optical properties, resulting in durable, high-performance materials that can be produced cost-effectively. These polymers are typically formulated as aqueous dispersion, which exhibit low viscosity, facilitating easy application. In addition, they are non-flammable and non-toxic, making water--based acrylic paints highly suitable as binding media in paintings. When applied to a surface, the water evaporates, causing the polymer particles to coalesce and form a solid, continuous film [4]. Acrylic paints often consist of complex mixtures of organic and inorganic compounds. Consequently, studying their internal interactions is of fundamental importance. The characterization of pigments is essential for planning conservation strategies. A comprehensive understanding of their composition enables the resolution of conservation issues through appropriate interventions. Indeed, only by fully understanding the properties of acrylic components and additives can the mechanisms of aging and degradation be elucidated [4]. This is achievable through advanced analytical techniques that allow for the precise identification and characterization of the constituent materials. In this study, acrylic pigments from the Maimeri Brera Acrylics Extrafine line were applied to wood and glass substrates to simulate real artworks and were analysed using \(\mu-\)Raman spectroscopy. The systematic application of \(\mu\)-Raman spectroscopy in the characterization of modern acrylic pigments provides a valuable resource for conservation science, offering significant practical implications for the identification and conservation of contemporary artworks, while contributing to the expansion and refinement of existing Raman spectroscopic data on these pigments. Raman spectroscopy has been extensively used in the field of material science for studying graphene [5], polymers [6], thin films [7], bi-dimensional systems [8], biological [9] and surfaces for Surface Enhanced Raman Spectroscopy (SERS) applications [10]. Among various diagnostic methods, Raman spectroscopy is recognized for its high sensitivity and specificity [11; 12; 13; 14; 15; 16; 17; 18]. This vibrational spectroscopy technique is based on Raman scattering--the inelastic scattering of light resulting from the interaction of a monochromatic, coherent beam of light with matter [19]. A conventional Raman setup consists of a spectrometer equipped with a light source, monochromator, sample holder and detector. In contrast, a micro-Raman spectroscopy integrates a confocal microscope with the spectrometer. The ability to operate at the submicrometer scale in a non-invasive and non-destructive manner makes micro-Raman spectroscopy a powerful tool for characterizing materials in cultural heritage studies [19]. The first applications of Raman spectroscopy in cultural heritage conservation date back to the late 1990s [19]. Initially, a major challenge was the lack of reference Raman spectral databases.