The mechanisms of red lead degradation were studied in a medieval Portuguese codex, Lorvão Apocalypse (1189), by Raman microscopy (µ-Raman) and micro-X-ray diffraction (µ-XRD). The range of pigments found for the illuminations is mainly limited to vermilion, orpiment and red lead. Micro-Fourier transform infrared spectroscopy (µ-FTIR) determined that the pigments were applied in a proteinaceous binding medium. In the red and orange colours, arsenic (As) was determined, by micro-energy dispersive X-ray fluorescence (µ-EDXRF), to be ranging 1-4% (wt %). For those colours, lead white and calcium carbonate were found as fillers whereas orpiment was applied as a pure pigment. Raman microscopy identified, unequivocally, the degradation product of red lead as galena [lead (II) sulphide, PbS].To determine the main factors affecting red lead degradation, a set of accelerating ageing experiments was designed to assess the influence of extenders and of the two other pigments, vermilion and orpiment. The experiments were followed by µ-Raman, µ-EDXRF and XRD. Raman microscopy results for the simulation of degradation of red lead, in the presence of orpiment, are in agreement to what was found in the Lorvão Apocalypse, galena being the main degradation product; also in common is a Raman band at ca. 810 cm −1 , which was attributed to a lead arsenate compound. It was concluded that in Lorvão Apocalypse, the degradation of red lead was a result of its reaction with orpiment.

The degradation of indigo and its water soluble derivative indigo carmine was investigated under light excitation in the presence and absence of molecular oxygen in solution (homogeneous) and gels (heterogeneous) media. Collagen and carboxymethylcellulose (CMC) aqueous gels were chosen to simulate a natural textile environment, wool and cotton, respectively. Isatin was found to be the major degradation product of indigo. In solution, the photodegradation quantum yields (Phi(R)) were in the order of 10(-4), with the exception of aqueous media (Phi(R) = 9 x 10(-6)), and dependent on the irradiation wavelength. In the case of indigo carmine the Phi(R) values were found to suffer a 2-fold increase upon going from water to gels. The results indicate the absence of degradation products involving singlet oxygen and suggest peroxides, or other oxygen based radicals, to have a key role in the degradation of indigo. Finally, the relevance of the simulation is discussed by comparing the main degradation products to those found in the blues of millenary Andean textiles.

Santa Maria de Alcobaça Monastery, a Cistercian monastery, was established in 1153, in the year of St. Bernard of Clairvaux's death. From the approximately 160 illuminated manuscripts produced during the late 12th to early 13th centuries, a set of 15 manuscripts was selected to characterize the medieval colour palette of this scriptorium, following an interdisciplinary study on Portuguese medieval illumination. Colour paints were fully characterized by Raman microscopy (RM), alongside m-Fourier Transform Infrared Spectroscopy and m-Energy dispersive X-ray fluorescence.The Alcobaça collection shows consistently the use of pink and grey paints, mostly achieved by mixing vermilion and/or an organic red, or a carbon-based black pigment with lead white, respectively. Lazurite was the chosen pigment for blue, being ubiquitous in the studied collection. Azurite was found in the lettering of only one manuscript (Alc. 433). Green is defined as bottle green, commonly seen in Portuguese medieval manuscripts, evidencing the loss of cohesion and adhesion to the support. RM and m-Fourier Transform Infrared Spectroscopy identify a copper complex with a protein, possibly verdigris based. The remaining colour palette comprises orpiment, red lead and two organic dyes (with yellow and dark red) not yet characterised. Darkening is observed for lead white in two manuscripts (Alc. 249 and Alc. 446). RM shows galena, a lead sulfide, as the degradation product of lead white, and a band at approximately 810 cm À1 , indicating the presence of an arsenatebased species. On Alc. 446, an intense broad band at approximately 339 cm À1 was also identified, most likely due to an orpiment-based solid phase in agreement with the reduction of orpiment or the arsenate-based species. A set of experiments was designed to assess the influence of orpiment on lead white degradation, corroborating the previous results and indicating the appearance of a new lead carbonate phase.