Multi-analytical characterisation of blotting sands on documents from religious orders in Portugal (16th-19th centuries)

Too little is known about areia de escrever, i.e., blotting sands, the intriguing particles sprinkled on freshly written scripts to accelerate the drying time of the ink. Blotting sands constitute a valuable but underestimated historical source.

This work investigated the blotting sands used on the account books of the religious houses scattered across continental Portugal and Madeira Island (16th-19th century). The sands were mainly composed of different minerals, predominately black sands, but in a few cases, minerals were found mixed with gums, paper cocoons or bone grates. The combined use of SEM-EDS, µ-Raman and FT-IR techniques uncovered the materials' chemical or mineralogical composition and morphology. This approach, allied with image analysis and statistics complemented with multivariate analysis, allowed us to look for trends between the samples and hypothesise about their provenance. Heavy minerals, such as ilmenite, hematite and almandine, were identified as major components, together with other silicates (e.g., quartz). Samples were dominated by medium-sized grains with shape features indicating texturally mature sediments resulting from a medium-to-long sedimentary transport. Due to shorter geological transport distances, Madeira Island was the exception, with more angular grains. This work allowed us to uncover blotting sands, value them as historical sources, and establish a roadmap for their use in Portugal, aiming to pave the way towards a more global context in Europe.