Choirbooks are historical heritage manuscripts used for the performance of vocal music in religious ceremonies in colonial times. This study aimed to understand the characteristics of choirbook manuscripts produced in the Real Audiencia de Quito during the 17th century. The methodology combined non-invasive techniques, such as infrared false-color imaging (IRFC) and X-ray fluorescence (XRF), together with spot analysis by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) and Fourier transform infrared spectroscopy with attenuated total reflection (FTIR-ATR). The analytical results revealed the use of pumice, chalk and lime carbonate as support materials in the manufacturing process and surface treatment of the parchment. In the illuminations, three pictorial techniques based on protein, polysaccharide and lipid binders were recognized, establishing that the pigments used with greater regularity in the illuminations were vermilion, minium, verdigris, orpiment, azurite, and indigo, preferably in a pure state. Materials used less regularly were also identified, such as yellow ochre, saffron, smalt, red ochre, and bone black, among others. Regarding the vulnerability of the pictorial materials, it was determined that, although most of the pigments exhibit chemical stability, they present some vulnerabilities associated with their intrinsic composition and the medium that contains them.

Quito, recognized as the first UNESCO World Cultural Heritage Site, holds a vast documentary legacy at constant risk of deterioration due to environmental, biological, and aging factors. Preserving these historical documents demands sustainable and non-invasive approaches. This study presents the first documented investigation in Ecuador on the use of ionizing radiation for the conservation of historical paper materials. Fifteen fragments, naturally detached from deteriorated documents housed in two major heritage repositories, the Biblioteca Nacional Eugenio Espejo and the Biblioteca Fray Ignacio de Quezada, were selected for analysis. Samples were irradiated with a Co-60 gamma source at doses of 4, 6, and 8 kGy at the “Francisco Salgado T.” Irradiation Center. To evaluate potential alterations, pre- and post-irradiation analyses were conducted using surface pH measurements, colorimetry (ΔE from CIELAB coordinates), and FTIR-ATR spectroscopy. The results showed no statistically significant changes in the analyzed parameters, suggesting that gamma irradiation at these doses does not compromise the structural or visual integrity of the paper. This work represents a pioneering step in Ecuador toward integrating scientific methods into cultural heritage preservation, supporting the safe application of ionizing radiation in the conservation of historical documents.