The Bodleian Libraries’ Conservation and Collection Care team were awarded a grant from the Cultural Heritage Advanced Research Infrastructures, Synergy for a Multidisciplinary Approach to Conservation/Restoration (CHARISMA). The grant enabled us to use a mobile laboratory for instrumental analysis (MOLAB) to characterise the colours present in the Libraries’ five pre-Hispanic and early colonial Mexican pictorial manuscripts: Codex Laud, Codex Bodley, Codex Selden, the Selden Roll, and Codex Mendoza.
Goals and outcomes
The Bodleian Libraries have a duty to preserve their collections, in order to guarantee their permanence and stability for present and future generations of scholars. As research libraries, we are also committed to studying our collections and to providing access to them for researchers worldwide. Due to the fragility of the codices, very little work had been done in the past to assess their materials and composition. Yet it is these very aspects that are critical to understanding the nature of these documents, their construction and their durability. The outcomes of the project will be:
- Learning more about the pictorial techniques and materials used in these five manuscripts;
- Answering key questions concerning both the history and the making of these codices;
- Minimising the unnecessary handling and piecemeal analysis of these unique items.
The project involved the non-destructive chemical characterization of pigments and colorants used in the manuscripts’ manufacture, in order to clarify the ancient Mesoamerican painting techniques and to compare the scientific results with those proceeding from similar analysis carried on in recent years on other Mesoamerican codices by the MOLAB (see Miliani et al. 2012). The MOLAB campaign was conducted thoroughly over five days working on each codex at the same time. The investigations involved different spectroscopic techniques:
- XRF – for the identification of preparation layers, pigments and possibly organic pigments/colorants and the supports/substrates for these colorants (with Raman and FTIR);
- FT-IR (mid and near) – for pigment, binder and support identification (and possibly to assess any conservation interventions), preparatory layers, identification of clay substrate types, investigation of areas of repair (with Raman and XRF);
- Raman – pigment and dyes (especially to look for possible indigoid-based pigments/colorants including shellfish purple and Maya blue) (with XRF and FTIR);
- Fiber-optic vis-NIR spectroscopy, fiber-optic UV-vis fluorescence and fluorescence time decay – identification of presence/location of organic substances and possibly identification of the substances/colorants used.
The non-invasive investigations were completed by imaging analyses such as UV fluorescence imaging and digital microscopy to obtain general information about the distribution of the fluorescent materials and indications on possible mixture of pigments/colorants and material consistency of the painting layers.