# Characterization of Waves in the Roman Wall Paintings of the Herculaneum Site (Italy)
###### Abstract  
A multi-analytical approach is proposed for the detection and quantitative characterization of waves in wall paintings from the Vesuvian area, in particular in the House of the Skeleton, the House of the Deer and the House of the two Atriums in Herculaneum (Italy). Different types of waves, of animal, vegetable, mineral and artificial origin, were investigated, as reference materials, by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and gas chromatography coupled with mass spectrometry (GC/MS). The obtained results were compared with those found on samples from the wall paintings of Herculaneum. By non-destructive techniques, Raman and FTIR spectroscopies, waves were generally found in the wall painting fragments investigated. A more quantitative characterization by GC/MS analysis, performed on three representative samples on the three houses, allowed highlighting the features of beesux. In addition to beesux, candellilla wax and an artificial wax, compatible with the formulated candellilla wax, were also detected. The presence of candellilla, a vegetable wax introduced in Europe after the sixteenth century, suggests maintenance works probably carried out with the aim of preserving the original colors of the paintings. In addition, by Raman and FTIR spectroscopies hematite and Egyptian blue pigments were identified. Calcite, aragonite and gypsum were also detected. W acronyms: 31 August 2022  
Accepted: 3 November 2022  
Published: 7 November 2022  
**Published: 7 November 2022**  
theory_\" has been formulated in this regard, supported by [PERSON] and [PERSON] [4]. They claim that Roman wall paintings were exclusively frescoed. According to this theory, the final aesthetic effect is similar to that of the _a secco_ technique thanks to the final polishing. The treatises illustrate that the technique used for the creation of the Vesuvian wall paintings consisted of applying to the wall two or three layers of calcium-based plaster, mixed with sand and marble powder. It is known that the process consisted of the creation of the painting on the still-fresh plaster, which, by drying, fixes the pigments in a stable and lasting way. Pompeian paintings can be dated between the end of the second century BC and the date of the Vesuvius eruption, 79 AD. At the time of the eruption of Vesuvius, unlike Pompeii, which was buried by a rain of ash and lapilli, Herculaneum was overwhelmed by a tide of mud and volcanic debris, which gave rise as it solidified to a sort of very hard tuff bank, between 8 and 15 m high, where the floors and ceilings of the buildings were preserved together with all the organic materials, such as wood, fabrics, paper, food: this fact enables a unique vision of the world of Roman private life. The houses were extensively decorated by the wall paintings that are their most extraordinary aspect. The knowledge of the organic compounds used as decorative or preservative materials in artistic paintings and the identification of binding media are the most important results in the conservation studies of the archaeological and historical artefacts and may reveal significant information on the development of the painting techniques [5; 6; 7]. Natural organic materials, like natural waves, have been used since ancient times for different purposes: as paint binders, waterproofing substances, sealants, protective surface coatings, ingredients of balms and cosmetics and for conservation processes in mummification, lighting candles and restoration practices [8; 9]. Natural waxes are highly heterogeneous materials containing esters of fatty acids with long-chain alcohols, free fatty acids and/or long-chain hydrocarbons [10; 11]. Waxes can be of animal (beeswax, lanolin, spermaceti wax, Chinese wax), vegetable (carnauba, candellilla, esparto wax, Japan wax) and fossil origin (paraffin wax, montan wax, cerese) [12].