Measuring surface roughness on stone: Back to basics

Styles profilometry, reflected-light image analysis and visual/tactile evaluation were tested as techniques for assessing roughness of abrasive-blasted stone. Measurement of microdrop water absorption time was also tested as a complementary technique. Instrumental techniques showed significant shortcomings when measuring surfaces of roughness similar to most weathered stone, as well as flame-finished surfaces comparable to tooled stone. Tactile comparison of surfaces was found to be a more practical and cost-effective technique. On historic masonry structures however, soiling and uneven weathering limit the usefulness of roughness as a property to be measured in evaluating cleaning techniques.