Assessment of the cleaning effect of HF cold plasma by statistical processing of photographic image

[Display omitted] •Capture of silver coin photographic image, before/after HF plasma cleaning treatment.•Characterization of some coin areas using statistical parameters and SEM–EDX analyses.•Statistical parameters, reveal the cleaning treatment, confirmed by SEM–EDX analyses. The assessment of cultural heritage objects cleaning by HF cold plasma treatment is hard to quantify. One method is based on direct comparison of photographic images acquired before and after treatment, a subjective evaluation, depending on the rigor and visual accuracy of the observer. An objective assessment is based on the analysis of statistical parameters of color histogram (mean, standard deviation, skewness), obtained by processing the photographic images taken before and after the cleaning. The paper aims to use the data of SEM–EDX analysis concerning the HF cold plasma cleaning of some objects in the statistical processing of their photographic images, extending the application domain and contributing to the understanding of statistical parameters significance (mean, standard deviation, skewness and kurtosis) in practice. The information concerning the changes induced by plasma active species on the object (coin) surface, revealed by statistical analysis, have been supplemented by SEM–EDX analyses, confirming the removal of contaminants from the coin surface.