A diagnostic study on folium and orchil dyes with non-invasive and micro-destructive methods

Organic dyes in illuminated manuscripts: a unique cultural and historic record

“…For the latter, no molecular structure could be proposed, despite the efforts of Krekel [39], and more recently of Aceto et al [40]. Regardless of being largely referred to in medieval treatises and other written sources-and, therefore, most likely widely used-unequivocal identifications of orcein purple in artworks are rare.…”

Characterization and Digital Restauration of XIV-XV Centuries Written Parchments by Means of Nondestructive Techniques: Three Case Studies

“…e re ectance spectrum shows two absorption bands at 540 nm and 580 nm (Figure 6(a)) that could be related to the presence of folium (or turnsole), a colorant produced by Chrozophora tinctoria plant, widely used on manuscripts [42]. e uorescence spectrum of the parchment (Figure 6(b)) exhibits a strong emission at shorter wavelengths (λ max 460 nm), while the purple ink also shows an emission at 605 nm that con rms the use of folium, as reported by Aceto et al [40].…”

“…37," ATR-FTIR analysis reveals the presence of calcite ( Figure S3 in Supplementary Materials), but no other compounds linked to the red ink are detected due to the presence of the black ink on the other side of the parchment which modi es the spectrum. Bromine (Br) was detected in some red initials of the three parchments (Table 1) and could be related to the presence of a purple dye [39,40] or to a conservation product, containing bromine, commonly used on ancient manuscripts [41]; however, it was not detected in the related parchments.…”

Surface-Enhanced Raman Spectroscopy: Using Nanoparticles to Detect Trace Amounts of Colorants in Works of Art

“…Castro et al (2014) combined minimally invasive SERS with non-invasive microspectrofluorimetry to identify, upon HF hydrolysis, lac dye reds in 12th-13th-century medieval illuminations from Portugal. Aceto et al (2015) successfully combined SERS and other micro-invasive techniques (such as matrix assisted laser desorption ionization-time of flight-mass spectrometry, and inductively coupled plasma-mass spectrometry) with FTIR, FT-Raman, fiber optic reflectance spectrophotometry, spectrofluorimetry, and XRF spectrometry to identify folium and orchil on various reference samples including dyed parchment-a mock up of the exceedingly rare purple codices. The authors claim that SERS was effective at identifying the colorants on the dyed parchment samples with and without extraction with formic acid, and report the first SERS spectrum of folium.…”