## 3 Results
Table 2 shows the results of EDX analyses performed on areas of 200 \(\times\) 200 \(\upmu\)m\({}^{2}\) on quartz fibre filters sampled with the four different cleaning methods at different times (for methods C and D, the results obtained after both 1.5 min and 5 min of aspiration are shown). Methods C and D are those that remove the highest amount of Ag (and similarly sulphur, i.e., these methods remove the most protective patina). It should be noted how method D also removes Au particles. It is important to stress that the method based on hydro-aspiration is therefore the least invasive on the metal threads. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Method** & **Time** & **Ag \%** & **Cu \%** & **Au \%** & **S \%** \\ \hline A & 1.5 min & 31.0 & 1.0 & - & 2.5 \\ \hline B & 1.5 min & 23.1 & - & - & 3.8 \\ \hline C & 1.5 min & 63.1 & - & & 5.3 \\ \hline  & 5 min & 55.7 & 2.2 & & 6.7 \\ \hline  & 1.5 min & 64.8 & & & 9.2 \\ \cline{2-6} D & 5 min & 49.3 & 4.9 & 15.5 & 7.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: EDX analysis acquired on punched areas (200 \(\times\) 200 \(\upmu\)m) of quartz fibre filter collected by the different cleaning methods after 1.5 or 5 min. The precision of the results reported is 5%. Figure 7: SEM images and the corresponding EDX analyses acquired on quartz fibre filters by method C (lower pressure-table) after 1.5 min (**a**) and 5 min (**b**). Ion chromatography has been applied to determine ion concentrations in the solutions produced during cleaning operations carried out at certain interval times as described previously in the text. Comparing the capability of removing soluble species such as chloride, nitrite, nitrate and sulphate, on the base of the results obtained by IC, it has been observed that, in general, the hydro-aspiration method allows removal of a higher quantity of ions. In Figure 8, the trend of ion concentrations in the solutions obtained cleaning by method A on two tapestry areas with gilded silver and gold threads is provided. Gold threads seem to be characterized by higher concentrations of soluble species retained in the solution during the cleaning. Finally, in order to determine the amount of carbonaceous material removed by the different cleaning methods, the quartz fibre filters collected by performing the cleaning operations on both a gold and a gilded silver yarn area were analysed using TOT. This technique is normally applied to quantify organic carbon (OC) and elemental carbon (EC) within atmospheric aerosols. In Figure 9, OC, EC and TC (total carbon is the sum of OC and EC) are provided. It is worth noting that elemental carbon, also known as black carbon due to its characteristic dark colour, is the main one responsible for the blackening of the surface. Analyses were performed on filters collected after 1.5, 3, and 5 min and after a 1.5 min rise. As can be observed, method A based on the hydro-aspiration method (Figure 9a,b) is able to remove more of both OC and EC and is the better choice compared with the other methods. However, by comparing the trends of OC and EC concentrations on the two areas, it can be observed that the gilded silver yarn releases a greater quantity of carbonaceous particles, and a further rinse is also necessary for a complete removal. It is worth noting that TOT measurements are performed on a selected filter area of 1.5 cm\({}^{2}\). Because of this, and since the deposition of particles on the quartz filter is not perfectly homogeneous, it was decided not to report the data as total quantity of OC, EC and TC on the filter, and consequently the values are reported as ug/cm\({}^{2}\). Figure 8: Trend of ion concentrations determined in the solutions obtained by cleaning two areas where gilded silver or gold threads are present, respectively, using method A.