Textile Materials: Reference Standards for Characterization Using Multispectral Analyses

The main objective of the research carried out by the Textile Conservation Sector at the Opificio delle Pietre Dure in Florence, Italy, was to verify the actual potential of optical investigation as means for identifying dyes on ancient textiles, and thus, to avoid taking micro-samples. For this we used samples of new fabrics dyed following procedures described in a number of fifteenth-century documents (es. PLICTO), and we systematically studied their different responses in electromagnetic radiation spectral bands. Soon, additional samples will be integrated into the small group of samples dyed in the 1980s, thereby expanding our database, which is still in its initial phases. The first group of samples consists primarily in silk and wool fabrics mounted on non-acid card stock. The multispectral techniques employed in the research are: visible light (VIS), Infrared reflectography (circa 950nm) imaged in false-colour infrared, UV fluorescence and reflected UV, also imaged in false-colour UV. All the images obtained with these methods were calibrated according to known reflectance standards and using reference colour profiles. The results obtained for the various samples proved to be quite interesting and provide the stimulus to define a more articulated research project in the future. Multispectral imaging techniques were supported with FORS (Fibre Optics Reflectance Spectra), which proved to be a complementary verification technique. The research technique was developed so that it could be used in the future, in a cost-contained environment and employing correct methodologies, by all laboratories and so that results could be compared with existing databases. Further, it has already been widely demonstrated, especially in the field of painting conservation, [1] that this type of diagnostic can provide important information for scientific and art historical documentation. OBJECTIVES OF THE RESEARCH The scientific examination of the materials in a work of art, both constituent and those resulting from past restoration interventions, their interactions and behaviour over time, is an essential element in the conservation of an object, and is an indispensable prelude to every restoration treatment. With increasing frequency, scientific innovations are being employed in the field of textile conservation for studying execution techniques and for the analysis of the conditions of an object. Textile materials, often fragile and except for a few cases not traditionally investigated, lend themselves to non-invasive investigation techniques rather than micro-destructive techniques. We are faced with various elements when we work to extract two essential pieces of data that characterize a textile piece (or any other object): dating and place of manufacture. These elements have already been addressed by CIETA in Lyon, France, during the 1950s. [2] They must evaluate the width, the selvages, the design repeat, the placement of the decorative elements and their relationship with the weave, the different types of spun yarns and their function within the weave, the material each one is made from, the twist method and the type of substance used in the dyeing. Without resorting to invasive analyses such as C14, it is clear that numerous pieces of information are required before being able to date a textile piece and to hypothesize a possible provenance. Here, we will address the dyed yarns that make up the textile, often analysed using HLPC, a micro1 9th International Conference on NDT of Art, Jerusalem Israel, 25-30 May 2008 For more papers of this publication click: www.ndt.net/search/docs.php3?MainSource=65