Optical micro-profilometry for archaeology Pierluigi Carcagnì a , Claudia Daffara b , Raffaella Fontana* b , Maria Chiara Gambino b , Maria Mastroianni b , Cinazia Mazzotta c , Enrico Pampaloni b , Luca Pezzati b a Istituto Nazionale di Ottica Applicata – Sez. di Lecce, via Barsanti, 73010 Arnesano (LE), Italy b Istituto Nazionale di Ottica Applicata - Largo E. Fermi 6 – 50125 Firenze, Italy c Dipartimento di Beni Culturali, Università di Lecce, via D. Birago 64, 73100 Lecce, Italy ABSTRACT A quantitative morphological analysis of archaeological objects represents an important element for historical evaluations, artistic studies and conservation projects. At present, a variety of contact instruments for high-resolution surface survey is available on the market, but because of their invasivity they are not well received in the field of artwork conservation. On the contrary, optical testing techniques have seen a successful growth in last few years due to their effectiveness and safety. In this work we present a few examples of application of high-resolution 3D techniques for the survey of archaeological objects. Measurements were carried out by means of an optical micro-profilometer composed of a commercial conoprobe mounted on a scanning device that allows a maximum sampled area of 280×280 mm 2 . Measurements as well as roughness calculations were carried out on selected areas, representative of the differently degraded surface, of an ellenestic bronze statue to document the surface corrosion before restoration intervention started. Two highly-corroded ancient coins and a limestone column were surveyed to enhance the relief of inscriptions and drawings for dating purposes. High-resolution 3D survey, beyond the faithful representation of objects, makes it possible to display the surface in an image format that can be processed by means of image processing software. The application of digital filters as well as rendering techniques easies the readability of the smallest details. Keywords: roughness, 3D survey, digital model, micro-profilometer, scanning device, conoprobe, archeometry. 1. INTRODUCTION Optical techniques are widely diffused and extremely well received in the field of conservation because of their effectiveness and safety [1-5]. The characteristics of being non-invasive make them particularly suitable for measuring frail (and precious!) objects. Many optical devices for three-dimensional survey are derived from industrial metrology, but the peculiarity of each artwork does not allow for a straightforward application. Challenges in artwork diagnostics are mainly due to shape irregularity and polychromy as well as the high-accuracy required to catch even the smallest details of a work of art. Surface cleaning is one of the most important and sometimes controversial stages of the conservation process: decisions have to be made regarding partial or complete removal of the outer patina, and restorers and conservators work would be considerably helped by the knowledge of surface morphology. A process of surface examination and analysis is, thus, critical to the definition and interpretation of corrosion or degradation in order to plan the restoration intervention. Moreover, a statistical analysis based on roughness calculation, can assess the condition of the object surface to monitor changes due to restoration intervention, surface decay due to wearing agents, or the evolution with time in terms of shape variations. When describing the surface integrity of an artwork, in fact, an important parameter to deal with it is roughness [6]. *lella@ino.it ; phone: + 39 055 23.08.313; fax: +39 055 233.77.55; www.ino.it ; http://arte.ino.it