Читать книгу Monument Future - Siegfried Siegesmund - Страница 420

In this paper we will analyse the accuracy of 3D optical microscopy to evaluate the impact of a common cleaning technique, called micro-sandblasting.

The cleaning of the stones with a view to preserving cultural heritage is a crucial phase that shows some risks, it is an irreversible process and sometimes can alters the surface and original finishing layer of the building work. There are no real procedures that quantify the degree of cleaning but only a guideline (Mecchi et al. 2008), (Revez, M. J.; Delgado Rodrigues, J., 2016), (Demoulin, T.; et al).

For years, the efforts of research in this sector, have been aimed at finding increasingly respectful solutions towards the materials treated and which, of course, are always in more or less precarious conditions.

To evaluate the effectiveness of the process of removing undesired materials (soiling, surface deposits, alterations of the surface due to degradation, etc.) (ICOMOS, 2008) laboratory tests are frequently carried out, which provide the removal of small portions of material to be subjected to laboratory analysis. (BS8221-1:2012, ASTM C1515-14, ASTM E1857-97).

The possibility of evaluating the removal of soiling, effectiveness in situ in a totally non-destructive way and at the same time quantifying any alterations of the original surface due to degradation is an objective that every conservator should set.

270The Alicona IF-Portable, used for this research, is a portable instrument, therefore it has the possibility of being mounted on a frame or on a trailer in order to carry out on-site acquisitions, thus able to meet one of the minimum requirements that allow the operator to verify the effectiveness of the intervention by monitoring the degree of cleaning and the harmfullness of the treatment, with the possibility of interrupting the operation at any time.

The Alicona IF-Portable microscope proves to be a suitable instrument for this purpose as there is no interaction with the surface, allowing a rapid acquisition.

An attempt was made to evaluate, by means of the Optical Alicona IF-Portable Profilometer acquisition, the efficacy and impact (harmfulness) of the cleaning following micro-sandblasting on stones of different hardness, as such is known to increase surface roughness in some cases (Carvalhão M., Dionísio A., 2015), (Pozo-Antonio J. S., et al. 2016).

The Alicona IF-Portable Optical Profilometer is generally used to perform high resolution 3D surface measurements for the evaluation of production quality in research and development in the laboratory. The key applications for this tool are used for surface analysis and characterization of materials in mechanical engineering, for example for the construction of tools and moulds, for precision mechanics, in the aerospace sector, in the automotive industry, in the field of science materials of all kinds, for the evaluation of corrosion, in electronics and for the development of medical devices. Thanks to its technical specifications, the Focus-Variation technique is used for both shape and roughness measurements (Avagliano R. et al. 2013).