## 3 Results  
Notwithstanding the importance of the issue of restoration of the tapestry by cleaning, there are few works in the scientific literature dealing with this aspect [2; 4; 9] or aimed at a preventive study for tapestries. For example, an interesting study is focused on the acquisition of information about protein breakdown at an early stage, long before fibre deterioration becomes visible [12]. It is worth noting that deterioration of materials causes breakdown of the molecular structure and results in a loss of strength, extensibility and durability, discoloration and fading, which affects the appearance of the textiles. The polymeric textile object of the present research was made by weaving yarns of different kinds, i.e., wool and silk yarns dyed by different colorants (whose nature has been investigated in other studies [13; 14]), gold metallic yarns and gilded silver metallic yarns (Figure 2). It is worth noting that the royal monogram was partially deteriorated showing abrasion of the thin gold layer and presence of corrosion products. The metallic yarns' degradation has caused the alteration of the original chromatic effect and what was once supposed to appear golden yellow, is now greyed and opaque. Elemental analysis such as SEM-EDX can provide useful information on both the state of preservation of the fibres and the chemical nature of the metal mordant used [15]. By means of SEM-EDX analyses both the composition of the metallic yams and the chemical nature of the degradation products were investigated. In particular silver corrosion products such as silver sulphide (Ag2S), silver oxide (Ag2O) and silver chloride (AgClCl) have been highlighted. These species form because of interaction with atmospheric pollutants such as aerosol particulate matter and SO2[16]. In Figure 3a, a SEM image of a yarn formed by the fibre core around which the metal yarn is wound is provided. The metallic yams, forming the coat of arms placed in the centre of the tapestry, are gold or gilded silver. The typical composition of a gilded silver yarn is shown in Figure 3b, whereas in Figure 3c an enlargement of the yarn is provided where the self-protection patina is visible, whose composition is shown in the EDX spectrum of Figure 3d. The problem of tapestry cleaning in the scientific literature, as already mentioned, has rarely been addressed, and to the authors' knowledge, there are only a couple of works from around 10 years ago [17; 18; 19] dealing with cleaning procedures. An important issue as regards the conservation of textile artefacts in museum environments [20] is represented by dust deposition on the work of art's surface, i.e., the deposition of the so called deposited particulate matter (DPM), which together with the absorption of gaseous pollutants such as SO2 (which is one if the main pollutants affecting air quality [21]) can react with the material giving rise to the formation of secondary species (as stated before). In the literature the effects of DPM on textile artefacts has been investigated in some French museums [19]. In order to evaluate the efficiency of the four different cleaning procedures considered in removing DPM from the tapestry surface, dirt was sampled through time tests (see Section 2.2). The cleaning methods applied are (further details on the specific features of each method are provided in [8; 9]):  
* Method A: innovative 'hydro-aspirating' system;
* Method B: immersion washing;
* Method C: low-pressure table;
* Method D: air aspiration. In Figure 4, as an example of the cleaning operations, the hydro-aspiration and air aspiration methods, are shown. The cleaning procedure was conducted on selected areas having dimensions of 3 \(\times\) 3 cm\({}^{2}\) on both the tapestry and some mock-up samples suitably realised. These mock-up samples were realized by putting mixtures of compounds on quartz fibre filters in order to simulate an artificial particulate matter. For this purpose, aluminium hydroxide, calcium carbonate, magnesium sulphate heptahydrate and sodium sulphate were employed.