On the effectiveness of phosphocitrate as salt crystallization inhibitor in porous materials. Case study of the roman mosaic of Orpheus and the beasts (Perugia, Italy)

Salt crystallization in porous materials constitutes one of the major causes of decay of buildings/archaeological sites in a wide range of environments. Desalination is among the most common methodologies of conservative treatment for salt decay. However, classic desalination techniques might be not suitable for long-term conservation. During the past decade interest has been an increasing towards crystallization inhibitors as a new means of controlling crystallization damage. This study deals with the first in-field application of an environment-friendly inhibitor system-phosphocitrate (PC). In particular, the case study of the Roman mosaic of Orpheus and the Beasts in Perugia (Italy) is presented. The inhibitor is completely soluble in water or alcohol, nontoxic, and easy to apply, thus enabling its use in accordance with the volatile organic compounds emission control and safety during the conservation works. Relevant samples from control and treated mosaic areas were collected and analyzed comparatively by means of Fourier transform-infrared spectroscopy, scanning electron microscopy, and energy dispersive spectrometry to study the potential of the inhibitor system in preventing/controlling salt damage in such archaeological site.