Cleaning your tools doesn’t mean that the tools are clean. A qualitative and quantitative perspective using confocal microscopy

Use-wear analysis has traditionally been criticised for relying heavily on subjective interpretation of the marks present on artefact surfaces. In recent years, confocal technology has started to make it possible to quantify and partially resolve this subjectivity. However, certain methodological aspects of great relevance for the analysis, such as the cleanliness of the pieces, have been significantly underestimated. This work aims to quantitatively verify whether qualitatively reliable − although not perfect- cleaning processes can modify the roughness readings of the surface of the tools. For this, 3D ISO 25178 parameters were analysed on an experimental rock crystal sample obtained with a confocal optical LED profilometer. The differences that we have found indicate the need not only to wash the samples, but also to check the degree of cleanliness of the materials once they are washed, which leads to the qualitative and especially quantitative importance of an adequate cleaning procedure before analysing the materials.