Number Of Admixtures Research Articles

Raman spectroscopic analysis of an important Visigothic historiated manuscript.

Raman spectroscopy has been used to study fragments of early Visigothic historiated manuscripts from the important mediaeval library at Santo Domingo de Silos which were a part of a Beato dating from the tenth to the mid-eleventh centuries. These fragments are from some of the oldest manuscripts in the scriptorium of the monastery. In this study, a comparison is made between the pigments and inks used on these manuscripts and those used in a previous study of the unique Visigothic Beato de Valcavado in Santa Cruz, Valladolid, completed in the year 970, which is noted for its quality of execution as well as its content and is remarkable eschatologically in being identifiable as the complete work of only a single scribe. For comparative purposes, the pigments and inks used in the Silos Monastery Beato and a series of historiated early manuscripts from mediaeval times through to the Renaissance also held in the monastic library were analysed. Raman spectroscopy identified a range of mineral and organic pigments such as cinnabar, orpiment, minium, azurite and indigo. In addition, a number of admixtures were found, for example, indigo and orpiment to produce vergaut (green) and a mixture of cinnabar with iron-gall ink and cerussite to produce darker and lighter shades of red. Some interesting conclusions were drawn about the use of iron-gall and carbon-based inks.This article is part of the themed issue 'Raman spectroscopy in art and archaeology'.

Quantitative analysis of multicomponent powders by full-profile refinement of Guinier–Hägg X-ray film data

Full-profile analysis of microdensitometer-measured Guinier–Hägg X-ray powder film data (strictly monochromatized Cu Kα1 radiation) [see Malmros & Thomas (1977). J. Appl. Cryst. 10, 7–11] is here extended to treat a multicomponent system where two of the components are refinable. The method is demonstrated for the case of: (a) α-Bi2O3/KCl (standard), and (b) CaF2/SiO2 (α-quartz) together with a Mg(OH)2 matrix. In (a), a weight ratio Bi2O3/KCl of 1:1 gave an experimental result of 0.96 (9):1. In (b), a number of admixtures have been studied in the range 1–60 wt% SiO2 all with 10 wt% CaF2. The agreement between weight ratios and profile refinement results suggests that the formal temperature factors function as effective absorption correction parameters. It is thus shown that approximate quantitative analysis is feasible from Guinier-Hägg diffraction data without any previously determined calibration curve. Moreover, the method permits the use of all available overlapping data in the refinement of a structure without needing to exclude data from known impurities [see Waltersson, Werner & Wilhelmi (1977). Cryst. Struct. Commun. 6, 231–235]. This feature is likely to prove the most common application of the method.