title: A diagnostic study on folium and orchil dyes with non-invasive and micro-destructive methods.
abstract: Folium and orchil are dyes of vegetal origin. Folium is obtained from Chrozophora tinctoria (L.) A. Juss., whereas orchil is obtained from Roccella and other genera of lichens. These dyes were used in the past to impart purple hue to paintings and textiles as substitutes for the more prised Tyrian purple dye, obtained from shellfish. Despite several citations in ancient technical treatises dating back at least to the Greek-Roman age, the identification of these dyes in artworks is rare. In the case of folium, an additional drawback is that its composition is presently unknown. In this work different non-invasive (FT-IR, FT-Raman, fibre optic reflectance spectrophotometry, spectrofluorimetry, X-ray fluorescence spectrometry) and micro-invasive (surface enhanced Raman spectroscopy, matrix assisted laser desorption ionisation-time of flight-mass spectrometry, inductively coupled plasma-mass spectrometry) techniques were used in order to increase the diagnostic information available on these dyes. Measurements were carried out on the dyes extracted from raw materials and on painted or dyed parchments. The possibility to distinguish between folium and orchil by chemical analysis is discussed.
authors.affiliation: Dipartimento di Scienze e Innovazione Tecnologica (DISIT), Università degli Studi del Piemonte Orientale, viale Teresa Michel, 11, 15121 Alessandria, Italy; Centro Interdisciplinare per lo Studio e la Conservazione dei Beni Culturali (CenISCo), Università degli Studi del Piemonte Orientale, via Manzoni, 8, 13100 Vercelli, Italy.. Electronic address: maurizio.aceto@mfn.unipmn.it.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Aceto
authors.affiliation: Dipartimento di Scienze e Innovazione Tecnologica (DISIT), Università degli Studi del Piemonte Orientale, viale Teresa Michel, 11, 15121 Alessandria, Italy.
authors.forename: Aldo
authors.initials: A
authors.lastname: Arrais
authors.affiliation: Dipartimento di Scienze e Innovazione Tecnologica (DISIT), Università degli Studi del Piemonte Orientale, viale Teresa Michel, 11, 15121 Alessandria, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Marsano
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Torino, via P. Giuria, 7, 10125 Torino, Italy; Nanostructured Interfaces and Surfaces Center of Excellence (NIS), via Giuria, 7, 10125 Torino, Italy. Electronic address: angelo.agostino@unito.it.
authors.forename: Angelo
authors.initials: A
authors.lastname: Agostino
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Torino, via P. Giuria, 7, 10125 Torino, Italy.
authors.forename: Gaia
authors.initials: G
authors.lastname: Fenoglio
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Torino, via P. Giuria, 7, 10125 Torino, Italy; Laboratorio analisi scientifiche, Direzione Ricerca e Progetti Cofinanziati, Regione Autonoma Valle d'Aosta, Loc. Lillaz, 7, 11020 Villair de Quart (AO), Italy. Electronic address: a.idone@regione.vda.it.
authors.forename: Ambra
authors.initials: A
authors.lastname: Idone
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Torino, via P. Giuria, 7, 10125 Torino, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Gulmini
mesh_terms: D001154:Art; D001203:Ascomycota / Q000737:chemistry; D004396:Coloring Agents / Q000032:analysis* / Q000302:isolation & purification; D019665:Euphorbiaceae / Q000737:chemistry; D005470:Fluorometry; D005638:Fruit / Q000737:chemistry; D013058:Mass Spectrometry; D010150:Paint / Q000032:analysis*; D013052:Spectrometry, X-Ray Emission; D013053:Spectrophotometry; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman
chemical_list: D004396:Coloring Agents
keywords: FORS; Folium; Orchil; Raman; SERS; Solid-state characterisation