This work aims at understanding the influence of the production processes and materials in the properties and long term behavior of acrylic sheet, i.e., poly(methyl methacrylate) (PMMA), a material generally considered very stable in museum collections. A comparative study was conducted in samples from cast acrylic sheets produced in the early 2000s, from which manufacturing details were known, and samples provided by the artist Lourdes Castro from acrylic sheets she had bought in the 1960s. Transparent and red opaque cast acrylic samples, containing cadmium red pigment, were used. All samples were artificially aged in a solarbox with irradiation λ > 300 nm for a total period of 8000 h, and alterations were followed by a multi-analytical approach which included Raman, infrared (FTIR-ATR) and UV-Vis spectroscopies; gravimetry; size exclusion chromatography (SEC); thermogravimetry (TGA); micro-indentation; colorimetry; and optical microscopy. Not all cast PMMA sheets presented similar stabilities. We have concluded that the production processes (which may include the polymerization conditions, the organic additives and the origin of the monomer) play a more important role in the properties and long-term behavior of these acrylic sheets than the presence of cadmium red and/or the age of the material.

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Acrylic sheet, also known by the commercial names Plexiglas or Perspex, consists of poly(methyl methacrylate) (PMMA). Attractive to artists since its development in the 1930s, it became especially popular during the 1960s. In Portugal, knowledge about its use by artists and its condition is scarce. In this work, the main Portuguese art collections were surveyed with the goal of gaining an overview of the use of acrylic sheet in the Portuguese art context and its current condition. The paper describes the methodology used and the results obtained regarding 137 artworks by 69 different artists registered as containing acrylic. Results show that this material is being used by Portuguese artists at least since the 1960s. It has been used in several artistic forms, from painting and sculpture to photography, installation, objects/reliefs, and artist books. Most of the artworks were in good or fair condition. The main problems observed were dust and dirt deposits, abrasion, and scratches.

This chapter examines how two polyesters, poly(methyl methacrylate) (PMMA) and poly(vinyl acetate) (PVAc) are explored with great ingenuity and creativity by the artists Ângelo de Sousa, Julião Sarmento and Lourdes Castro. Their fascination with these novel materials is revealed in interviews, which also show how these artists selected and transformed them into works of art. The case study approach using specific examples illustrates the relations between the molecular properties of PMMA and PVAc and factors related to social and artistic choices. The outstanding optical properties of PMMA and the possibility to transform sheets of PMMA into complex three-dimensional shapes were pivotal for its selection by Lourdes Castro and Ângelo de Sousa, respectively. This chapter also analyses the artists' technical choices and the impact these choices had on the conservation of their works. The way Ângelo de Sousa and Julião Sarmento played aesthetically with vinyl emulsions will have a direct effect on the ageing of their paintings. Julião Sarmento knows that the pristine white backgrounds of his “White series” paintings will yellow over time, while Ângelo de Sousa made every effort to protect his works in PVAc from ageing, adding layers of PVAc varnish on top of the painting and selecting the most durable colourants.