Chemical cleaning of encrustations on archaeological ceramic artefacts found in different Italian sites

The micro-chemical and micro-structural nature of inorganic thick encrustations, deposited during long-term archaeological burial on Roman, Greek and medieval ceramic artefacts and obscuring significant decoration details, were investigated by means of scanning electron microscopy combined with energy-dispersive spectrometry, optical microscopy, X-ray photoelectron spectroscopy, X-ray diffraction and differential thermal analysis and thermogravimetry. Analytical results showed the presence of carbonates mixed with low amounts of silicate, chlorides, sulphates and phosphates containing Ca, Fe, Na, K, Al and Ti. Extensive preliminary comparative trials and different chemical cleaning methods and materials were used to remove the thick carbonatic encrustations without altering the underlying coloured decoration layers. The micro-chemical and micro-morphological characterisation of the cleaned ceramic surfaces showed that a styrene-divinylbenzene copolymer cationic resin with fine particle size represents a reliable and effective cleaning material when applied under controlled conditions (temperature =30 °C, relative humidity =100%, application time =24 h) by using a simple, low-cost and safe procedure.