Near infrared reflectography for deciphering obscured (whitewashed or ablated) epigraphs

Infrared reflectography (IRR) is a non-destructive imaging technique based on the different optical behaviour of visible and near infrared (NIR) radiation through a thin pictorial layer. This effect is a consequence of both lower NIR absorption and reduced NIR scattering due to the particle size smaller than the wavelength. Here we present an interesting and, to our knowledge, new application of this technique to ancient multi-layered epigraphs, showing its useful application in archaeology. Both tests on laboratory samples and preliminary tests on the field show that it is possible to use IRR taken with a vidicon wide spectral range camera (let us call this NIR reflectography (NIRR) to underline the wide spectral range including almost all NIR, but excluding thermal infrared radiation), to read inscriptions 'deleted' by means of a whitewashing layer. The field tests carried out on a multi-layer inscription 'notice board' in Herculaneum have shown that NIRR can also be useful in integrating some gaps of the currently visible layer inscription and in reconstructing the layout of the inscription wiped off by mechanical abrasion. All these applications are of much interest since ancient Greek and Latin public documents were frequently written with black pigment on whitewashed boards and 'wiped off' when the inscription was no more required.

[1]  W. Vargas,et al.  Applicability conditions of the Kubelka-Munk theory. , 1997, Applied optics.

[2]  Nicola Ludwig,et al.  A new methodology for comparing IR reflectographic systems , 2007 .

[3]  J. R. J. van Asperen de Boer,et al.  Infrared reflectography: a method for the examination of paintings. , 1968 .

[4]  Molly Faries.  Some Thoughts on the Infrared Reflectogaphy (IRR) Workshop Experience , 2000 .

[5]  M. Rigdahl,et al.  Enhancement of the light-scattering ability of coatings by using hollow pigments , 1994 .

[6]  S. Miklavcic,et al.  Revised Kubelka-Munk theory. II. Unified framework for homogeneous and inhomogeneous optical media. , 2004, Journal of The Optical Society of America A-optics Image Science and Vision.

[7]  L. Colombo.  I colori degli antichi , 2003 .

[8]  Sophia Sotiropoulou,et al.  Panselinos’ Byzantine wall paintings in the Protaton Church, Mount Athos, Greece: a technical examination , 2000 .

[9]  E. Lima,et al.  Aluminum Phosphate Particles Containing Closed Pores: Preparation, Characterization, and Use as a White Pigment , 1996 .

[10]  Li Yang,et al.  Revised Kubelka-Munk theory. I. Theory and application. , 2004, Journal of the Optical Society of America. A, Optics, image science, and vision.

[11]  P. Kubelka,et al.  New Contributions to the Optics of Intensely Light-Scattering Materials. Part I , 1948 .

[12]  Charles F. Merbs,et al.  Examination of Tattoos on Mummified Tissue using Infra-red Reflectography , 2001 .

[13]  Joyce Plesters,et al.  I colori pompeiani , 1969 .

[14]  M. Ainsworth.  Implications of Revised Attributions in Netherlandish Painting , 1992, Metropolitan Museum Journal.

[15]  Li Yang,et al.  Revised Kubelka-Munk theory. III. A general theory of light propagation in scattering and absorptive media. , 2005, Journal of the Optical Society of America. A, Optics, image science, and vision.

[16]  J. A. D. Boer,et al.  REFLECTOGRAPHY OF PAINTINGS USING AN INFRARED VIDICON TELEVISION SYSTEM , 1969 .

[17]  John K. Delaney,et al.  Improved visualization of underdrawings with solid-state detectors operating in the infrared , 1994 .

[18]  P. J. Rhodes,et al.  Public Documents in the Greek States: Archives and Inscriptions Part II , 2001, Greece and Rome.

[19]  Gregory H. Bearman,et al.  Imaging the past: recent applications of multispectral imaging technology to deciphering manuscripts , 2003, Antiquity.

[20]  G Gouesbet,et al.  Four-flux models to solve the scattering transfer equation in terms of Lorenz-Mie parameters. , 1984, Applied optics.

[21]  J. R. J. van Asperen de Boer.  Infrared Reflectograms of Panel Paintings , 1966 .

[22]  P. Rhodes.  Public documents in the Greek states: archives and inscriptions1 , 2001, Greece and Rome.