Effects of mechanical cleaning by manual brushing and abrasive blasting on lime render coatings on Architectural Heritage

This research studies the effects of mechanical cleaning by brushing and by abrasive blasting on the lime render coating of a facade. After analysing the properties of the material, the deposits to be removed and their possible influence on the treatment, different cleaning tests were made by manual brushing and by blasting with three varieties of abrasives at 45[degrees] and 75[degrees] angles, keeping the other parameters constant. Taking the restorer's perspective as a starting point, and in order to fulfil the practical requirements of an intervention, tests were evaluated with macro-photography, USB digital microscope and stereomicroscope with 3D visualization and measurement. From the results can be concluded that abrasives with low friability and greater grain size than the space between mortar aggregates blasted at a 75[degrees] angle reduce the differential erosion compared to other abrasives; although manual brushing has less impact on the surface.Original Abstract: En este trabajo se estudian los efectos de las limpiezas mecanicas con cepillado y con proyeccion de abrasivos sobre un revestimiento exterior de cal. Tras documentar las propiedades del material, de los depositos superficiales y de su posible influencia en el tratamiento, se realizaron diferentes catas de limpieza con cepillado manual y con proyeccion de tres abrasivos con angulos de 45[degrees] y 75[degrees] manteniendo constantes el resto de parametros. Partiendo de la vision del conservador-restaurador y de un caracter practico segun las necesidades reales de intervencion, los ensayos se evaluaron con macrofotografia, microscopio digital USB y microscopio estereoscopico con visualizacion y medicion en 3D. De los resultados se determina que los abrasivos de baja friabilidad y granulometria mayor que el espacio entre los aridos del mortero proyectados con un angulo de 75[degrees] reducen la erosion diferencial en comparacion a otros abrasivos, aunque el cepillado manual altera menos la superficie.