Comparative Study of Fourier Transform Infrared Spectroscopy in Transmission, Attenuated Total Reflection, and Total Reflection Modes for the Analysis of Plastics in the Cultural Heritage Field Marcello Picollo, a, * Giovanni Bartolozzi, a Costanza Cucci, a Monica Galeotti, b Veronica Marchiafava, a Benedetto Pizzo c a Nello Carrara Institute of Applied Physics of the National Research Council (IFAC-CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy b Opificio delle Pietre Dure (OPD), Via Alfani 78, 50125 Firenze, Italy c Tree and Timber Institute of the National Research Council (IVALSA-CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy This study was completed within the framework of two research projects dealing with the conservation of contemporary artworks. The first is the Seventh Framework Project (FP7) of the European Union, Preservation of Plastic ARTefacts in Museum Collections (POPART), spanning years 2008–2012, and the second is the Italian project funded by the Tuscan Region, Preventive Conservation of Contemporary Art (Conservazione Preventiva dell’Arte Contempo- ranea (COPAC)), spanning 2011–2013. Both of these programs pointed out the great importance of having noninvasive and portable analytical techniques that can be used to investigate and characterize modern and contemporary artworks, especially those consisting of synthetic polymers. Indeed, despite the extensive presence of plastics in museum collections, there is still a lack of analytical tools for identifying, characterizing, and setting up adequate conservation strategies for these materials. In this work, the potentials of in situ and noninvasive Fourier transform infrared (FT-IR) spectroscopy, implemented by means of portable devices that operate in reflection mode, are investigated with a view to applying the results in large-scale surveys of plastic objects in museums. To this end, an essential prerequisite are the reliability of spectral data acquired in situ and the availability of spectral databases acquired from reference materials. A collection of polymeric samples, which are available commercially as ResinKit, was analyzed to create a reference spectral archive. All the spectra were recorded using three FT-IR configurations: transmission (trans), attenuated total reflection (ATR), and total reflection (TR). A comparative evaluation of the data acquired using the three instrumental configurations is presented, together with an evalua- tion of the similarity percentages and a discussion of the critical cases. Index Headings: Polymers; Noninvasive Fourier transform infrared spectroscopy; FT-IR; Noncontact FT-IR; Total reflection; Contem- porary art. INTRODUCTION The word plastic literally means ‘‘moldable.’’ This term is commonly used to indicate synthetic and semi- synthetic organic polymers that have a high molecular weight and are made up of specific units (monomers) linked to form long chains. The chemical–physical properties of plastics may be designed by varying the production processes and the formulations. Indeed, by starting from the same basic resin, the final formulation may be varied by adding several types of additives (colorants, fillers, plasticizers, etc.), which then make it possible to control precisely the characteristics of the finished material. This exceptional versatility of plastics is indeed the reason for their pervasive and capillary diffusion into every field and aspect of our lives. Nowadays, as culture and art reflect and dip into the historical context and into daily life, plastics have also become part of our cultural heritage and are widespread in art collections, museums, and art galleries. The first documented use of plastics as artistic materials dates back to the pioneer works of Naum Gabo in the early 1900s. 1 Since then, recourse to synthetic polymers in the art field has constantly increased, reaching a high point in the 1960s. At present, resorting to synthetic polymers is ubiquitous among artists, and plastics are definitely considered to be also a class of artistic materials. In addition to artistic produc- tion, the appearance of plastics in museums and galleries is also related to design, ethnographic collec- tions, and technical collections, as well as film archives. Consequently, a notable percentage of artworks and valuable objects consisting of synthetic and semi- synthetic polymers are kept in museums, and these are classified as items to be preserved for future genera- tions. Despite this fact, the problem of the conservation of plastics in art collections had been disregarded until recently because, for a long time and due to widespread misconception, plastics have been considered imperish- able materials. The need to adopt systematic strategies for the conservation of plastic objects, in a way analogous to other, more traditional materials in collections, has been completely recognized only in recent decades. Such an increased awareness has given rise to a new research area aimed at filling in the lack of knowledge, practices, and methodologies for preserving plastics in collections. 2–4 Several projects devoted to the safeguarding of contemporary art have recently been launched, such as the Preservation of Plastic ARTefacts in Museum Collections (POPART), Conservazione Pre- Received 5 July 2013; accepted 19 November 2013. * Author to whom correspondence should be sent. E-mail: m.picollo@ ifac.cnr.it. DOI: 10.1366/13-07199 Volume 68, Number 4, 2014 APPLIED SPECTROSCOPY 389 0003-7028/14/6804-0389/0 Q 2014 Society for Applied Spectroscopy