title: Identification of natural red and purple dyes on textiles by Fiber-optics Reflectance Spectroscopy.
abstract: Understanding dye chemistry and dye processes is an important issue for studies of cultural heritage collections and science conservation. Fiber Optics Reflectance Spectroscopy (FORS) is a powerful technique, which allows preliminary dye identification, causing no damage or mechanical stress on the artworks subjected to analysis. Some information related to specific light scattering and absorption can be obtained in the UV-visible and infrared range (300-1400nm) and it is possible to discriminate the kind of support fiber in the near infrared region (1000-2500nm). The main spectral features of natural dye fibers samples, such as reflection maxima, inflection points and reflection minima, can be used in the differentiation of various red natural dyes. In this work, a set of dyed references were manufactured following Mexican recipes with red dyes (cochineal and brazilwood) in order to determine the characteristic FORS spectral features of fresh and aged dyed fibers for their identification in historical pieces. Based on these results, twenty-nine indigenous textiles belonging to the National Commission for the Development of Indigenous People of Mexico were studied. Cochineal and brazilwood were successfully identified by FORS in several pieces, as well as the mixture of cochineal and indigo for purple color.
authors.affiliation: Instituto de Física, Universidad Nacional Autónoma de México, Circuito de la Investigación S/N, Ciudad Universitaria, Coyoacán, Mexico City 04510, Mexico. Electronic address: maynez@fisica.unam.mx.
authors.forename: M A
authors.initials: MA
authors.lastname: Maynez-Rojas
authors.affiliation: Laboratorio Nacional de Ciencias para la Investigación y Conservación del Patrimonio Cultural, Instituto de Física, Universidad Nacional Autónoma de México, Circuito de la Investigación S/N, Ciudad Universitaria, Coyoacán, Mexico City 04510, Mexico. Electronic address: casanova@fisica.unam.mx.
authors.forename: E
authors.initials: E
authors.lastname: Casanova-González
authors.affiliation: Instituto de Física, Universidad Nacional Autónoma de México, Circuito de la Investigación S/N, Ciudad Universitaria, Coyoacán, Mexico City 04510, Mexico. Electronic address: sil@fisica.unam.mx.
authors.forename: J L
authors.initials: JL
authors.lastname: Ruvalcaba-Sil
mesh_terms: D000818:Animals; D001578:Benzopyrans / Q000737:chemistry; D001688:Biological Products / Q000737:chemistry*; D002329:Carmine / Q000737:chemistry; D004396:Coloring Agents / Q000737:chemistry*; D032561:Cotton Fiber; D005336:Fiber Optic Technology / Q000379:methods*; D007091:Image Processing, Computer-Assisted; D008027:Light; D013057:Spectrum Analysis; D013784:Textiles; D014935:Wool
chemical_list: D001578:Benzopyrans; D001688:Biological Products; D004396:Coloring Agents; D002329:Carmine; C044362:brazilin
keywords: FORS; Mexican textiles; Non-invasive analysis; Red dyes