Microscopic techniques (LM, SEM) and a multi-analytical approach (EDX, FTIR, GC/MS, Py-GC/MS) to characterise the decoration technique of the wooden ceiling of the House of the Telephus Relief in Herculaneum (Italy)

The House of the Telephus Relief in Herculaneum (Naples, Italy) is a Roman domus, buried by the eruption of Mount Vesuvius in AD 79. The house had a wooden roof with decorated ceiling, which was discovered in 2009. The roof represents an extraordinary archaeological find and, although it was found mainly disassembled, some of its wooden decorative panels are still almost intact. Some portions of the original polychrome decoration and traces of gilding are still preserved.Within the framework of the Herculaneum Conservation Project, a diagnostic study was undertaken to characterise the materials used in the polychrome decoration and to assess the technique used by Roman painters to decorate the ceiling.Micro samples (c. 500. μg) of paint were analysed with a multi-analytical approach. The micro-morphological characterisation of the pigments and the paint stratigraphy was assessed using light (LM) and scanning electron microscopes (SEM). X-ray microanalysis (EDX) coupled with SEM and Fourier transform infrared spectroscopy (FT-IR) were used to investigate the inorganic components. Gas chromatography/mass spectrometry (GC/MS) and pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC/MS) were used to identify the binding media and other organic materials. The nature of the sediment, where the findings had been embedded, was also investigated.The acquired data revealed that a tempera painting has been applied. Egg was used as binder, whereas lime, red and yellow ochre, and caeruleum were used as white, red, yellow and blue pigments, respectively. The paint was directly applied onto the wood surface. Some decorations involved the application of gold leaf: unfortunately, no trace of the mordant or adhesives was found. The results also highlighted some issues related to the state of preservation of the artefact, thus contributing to the planning of conservation strategies