Non-invasive Observation of Internal Structure of a Giotto's Masterpiece by THz Imaging

－The modern figure on the medieval preparation is revealved －

February 25, 2009

National Institute of Information and Communications Technology (Tokyo, Japan) have applied THz imaging to the analysis of a Giotto's masterpiece, "Polittico di Badia" (c.a. 1300) at the Uffizi Gallery (Florence, Italy), as a collaborative work with the Istituto di Fisica Applicata "Nero Carrara"-Consiglio Nazionale delle Ricerche (Florence, Italy). This is the first ever internal observation of a tempera masterpiece with maps of the layer of interest, and was introduced in a newsletter of International Institute for Conservation of Historic and Artistic Works, "News in Conservation", February issue.

The non-destructive cross section image clearly shows the layer structure which contains a base of wood, a gypsum layer for smoothing wooden surfaces, a cloth, a preparation gypsum, and finally painting layer, It proves that Giotto followed the early Renaissance polyptychs manner for the preparation.

This three dimensional non-invasive observation of paintings cannot be realised by conventional method. The findings should attract art historians interests and can give practical information to conservators.

Technology used in this work

Terahertz (THz) rays can penetrate opaque materials, and can analyse multi-layer objects. Its time domain spectroscopy and tomography has been used to interrogate tablets of medicine and THz imaging has been also applied to various security issues. T-rayTM4000 of Picometrix (Michigan, USA) was used for this experiments, and data was analysed based on the spectral database developed by NICT.

Future work

This tempera polyptych "Polittico di Badia" had been under restoration by Stefano Scarpelli in the Uffizi Gallery in Florence, and will be at the exhibition "Giotto e il Trecento" in Rome from 6 March. A catalogue of the restoration activities with additional scientific analysis results will be published in the future.