XRF Study of Mexican Iron Gall Inks: Historical and Geographical Overview of their Chemistry

摘要

Over 2000 micro-X-Ray Fluorescence (μ-XRF) measurements of iron gall inks were collected at the General Archive of the Nation in Mexico (Archivo General de la Nacion, AGN). The portable X-Ray system SANDRA permitted detection of common elements present in all iron gall inks (e.g. Ca, Fe, S, etc.) as well as characteristic traces and impurities (e.g. Cu, Ni, Zn, Pb, etc). The documents in the data set originate from all over Mexico and are dated between the 16th and 19th centuries. All manuscripts were well preserved. Extensive statistical processing of the relative X-Ray intensities revealed common features in groups of documents with the same provenance. Among the findings, there is a progressive trend to complex mixtures from the beginning of the 16th century to the 17th. A reverse trend was observed for the following century. Zinc, lead and seldom arsenic, chromium and mercury seem characteristic for northern areas whereas manganese seems common to the vast majority of studied inks. As a general concern in conservation research, special attention was addressed to copper, as it is known to have additive effects to the degradation of cellulose. This metal seems fairly common to Mexican inks, especially during 18th century. To the best of our knowledge, this is the first examination taken to such a large number of inks. This study contributes to the more-focused development of suitable treatments that tailor specific needs, since they are to be based on of ink's composition. It sets a precedent for the study of these inks in the Americas and allows conservators and historians to gain further insight into the history of their usage in Mexico.