Modern acrylic paints probed by optical coherence tomography and infrared reflectography

Cont emp orar y art is partic ular ly del icate as the s ynthe tic ma teria ls use d for their real iz atio n are of poore r qual ity and dura bili ty than the tradit ion al mater ials . It foll ows that the contem por ary artwork s often requir e immine nt rest orat ions as wel l as in-d ept h analy tical studi es of the consti tut ing mate rial s. The non-in vasi vene ss of the sci- ent ific me thod s is a key issue in the dia gnost ics of contem por ary art beca use it minim izes the need of sampl ing. In this respec t, the poten tia l of Opt ical Cohere nce Tomo grap hy (OCT) imagin g to probe the inter nal struc ture of the comm erc ial acrylic paint laye rs, as a func tio n of their thickn ess , was inve stig ated and compar ed with that of the near infrared (NIR) reflectogr aphy. In support of these measur ements, micro-profilo metry, an interferome tric techn ique with micromet ric depth reso lution, was used to measur e the paint layer thickne sses. We show that for some painted materials there is a limited possibilit y to visuali ze the underdrawings , when investi gated by both OCT and NIR reflec tography. This is owed to either the absorption of the illumin ation wavelength by the pain t layer (Cob alt- base d paints) or the mult iple pho ton scat teri ng effect (pr esen ce of TiO 2 ).