ABSTRACT
In year 2000, due to some imminent cleaning works on the walls of the cloister of the monastery of San Millán de la Cogolla, de Yuso, in La Rioja (Spain) and their foreseeable negative impact in a group of graffiti, which were known although not studied or even recorded at that time, an emergency labour was undertaken in order to trace them in plastic sheets. However, the sheets were cumbersome so no further studies were done until year 2016, when they were photographed and digitized.
On the other hand, there was no appraisal concerning the conservation status of the engravings after the cleaning, in fact, it was even thought that they were totally lost. This situation of uncertainty was tackled in 2018 with a series of explorations in different parts of the cloister, in which the visual reconnaissance was complemented with a range of image techniques, in particular: raking light photography (both with fixed and moving lighting), short distance convergent photogrammetry with image enhancement, Reflectance Transformation Imaging (RTI) and structured-light scanning.
The present work describes the techniques, their practical implementation on site and the data processing. Finally, the applicability of each one –and their possible combination- for the identification of graffiti and the determination of their state of repair are discussed.
