Volume 36, Issue 3 -

Princeton University Library’s rare sixteenth-century polychrome Aztec picture map on deerskin vividly portrays the conversion of the Aztecs to Catholicism during the Early Colonial Period of the Spanish Conquest. A non-invasive technical examination was conducted to identify the colourants and the species of the animal hide support used in the creation of the map. Analysis included spectroscopic techniques such as attenuated total reflectance-Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy. Light microscopy and UVA fluorescence were also employed as tools. Results of the technical examination found the presence of cochineal, bone black, Maya blue, which are indigenous colourants traditionally associated with Mesoamerica, and a layer of an unknown greenish-yellow dye over Maya blue to create the colour green. The examination also discovered what appears to be an orange-yellow gamboge-like substance known as American (sometimes called Mexican) gamboge, which is indigenous to Mexico and parts of Central and South America. Its plant family is Hypericaceae, which is very closely related to Clusiaceae. Clusiaceae is the Southeast Asian and Indian plant family of gamboge, which is commonly used as a pigment in Western, Indian and Asian art. The study’s exposure of the obscure substance may spur more research into its use as a colourant of the Mesoamerican palette. The paper also hopes to add to the overall knowledge of Mesoamerican materials in order to better understand aspects of their conservation and preservation.

The deacidification of historic paper objects has evolved into a method that is applied in mass-scale in some archives and libraries. While the impact of the deacidification reagents on paper is quite well researched, knowledge about the behavior of colours and dyes is more limited. Our study focused on the influence of paper deacidification by the Book Saver® process on eight different dyes applied on paper, as well as on the paper support itself. Accelerated ageing in moist and warm conditions (80°C, 65% relative humidity) was applied to investigate the stability of the dye layer on top of the paper, with respect to their chemical, optical and spectroscopic attributes. The Book® deacidification process increased the pH of the aqueous extract and an alkaline reserve was created. FTIR spectroscopic measurements showed that deacidification suppresses acid hydrolysis of paper. The variations in UV-Vis reflectance spectra and in total colour difference of the dye layer evidenced the changes in the structure of dyes caused by accelerated ageing, but the extent of the changes differs depending on the dye. We can conclude that some dyes are more prone to changes by deacidification than others.

Long-time preservation of manuscripts depends on the stability of their support. One of the most important degradation processes of paper manuscripts containing iron gall ink is the acid hydrolysis of cellulose. The heterogeneity of the distribution of their constituent materials, together with the defined position of ink as a source of degradation agents, makes it difficult to obtain reliable and detailed information about degradation processes. The aim of this study is to contribute to the knowledge of the acid degradation process by looking at the distribution of relevant variables (pH, acidity and alkaline reserve) on real untreated iron gall ink containing manuscripts at different degradation stages. The study discusses the well-known differences between surface and cold extraction pH determination. It corroborates the relationship between pH, acidity and alkalinity and degradation stages, pointing out that acidity values for some manuscripts in apparent good condition are not far from those obtained for degraded manuscripts. The results indicate that in some partially degraded manuscripts, the coexistence of acid areas and areas with an alkaline reserve which do not participate in the neutralization process is possible. The role of water as a solvent for this equilibrium has also been evaluated.