## 2 Materials and Methods  
### Sample Preparation  
In this study, two samples were made to reproduce plasterwork of the Hispano-Muslim tradition of the 12 th-15 th centuries, called \"P1\" (sample 1) and \"P2\" (sample 2). The three layers that make up this type of plaster have been reproduced: the first layer corresponds to 80-90% Vigor(r) (r) VIGLIETTA Matteo SpA, Parma, Italy) plaster coating on a ceramic support of dimensions 30 \(\times\) 15 \(\times\) 1.5 cm, followed by the second layer, preparation layer, made with Vigor(r) (r) VIGLIETTA Matteo SpA, Parma, Italy) plaster mixed with lime and CTS(r) (r) Copyright C.T.S. Espana S.L., Madrid, Spain) animal glue as organic binder (_v:v_-1:1.1/4) [7]. Finally, there is the third layer of polychromy, for which two representative pigments were selected: vermilion (42000 Kremer(r),r) Kremer Pigmente, Aichstetten, Germany) and azurite (10200 Kremer(r),r) Kremer Pigmente, Aichstetten, Germany) [10]. Both pigments were mixed with animal glue and Arabic gum as a binder, giving rise to a total of 4 evaluation samples (\"Original layers\" in Table 1) (Figure 1): azurite with animal glue (_v_/_v_ 1:1), azurite with Arabic gum (_v:v_ \(-\)1:1), vermilion with animal glue (_v:v_\(-\)1:1/2), and vermilion with Arabic gum (_v:v_\(-\)1:1/2)  
Subsequently, two oil colors were applied, simulating the types of alteration studied in this research: linseed oil binder ([PERSON](r),r) (r)2025 Art & Colour, Kavala, Greece) mixed with ultramarine blue (45000 [PERSON](r),r) Kremer Pigmente, Aichstetten, Germany) and titanium white (46200 [PERSON](r),r) Kremer Pigmente, Aichstetten, Germany) (_v:v_- 1:1/3:1/4) and linseed oil mixed with yellow ochre pigment (40301 [PERSON](r),r) Kremer Pigmente, Aichstetten, Germany) (_v:v_\(-\)1:1/2). Each support was divided into three bands: band B, which corresponds to ultramarine blue and titanium white with oil binder; band A, which maintains a check of the original polychrome layer; in band yellow, ochre was applied with oil binder on top of the original polychrome layer (\"Repainting\" in Table 1) (Figure 3). The samples are stored under controlled laboratory conservation conditions, with 45-50% relative humidity, at a temperature of 20-21 \({}^{\circ}\)C, without natural or artificial exposure.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{4}{c}{**Original Layer**} & \multicolumn{4}{c}{**Repainting**} \\ \cline{2-9}  & **Pigment** & **Binder** & **Band** & **Name** & **Pigment** & **Binder** & **Band** & **Name** \\ \hline \multirow{6}{*}{P1} & \multirow{6}{*}{Azurite (a)} & Animal & \multirow{2}{*}{A} & \multirow{2}{*}{P1 aCa(A)} & \multirow{2}{*}{P1 aCa(A)} & \multirow{2}{*}{Linseed (C)} & \multirow{2}{*}{B} & \multirow{2}{*}{P1 aCa(B)} \\  & & Glue (Ca) & & & & & Ochre & C & P1 aCa(C) \\ \cline{3-8}  & & & & & & & & \\ \cline{3-8}  & & Arabic & \multirow{2}{*}{A} & \multirow{2}{*}{P1 aGa(A)} & \multirow{2}{*}{P1 aGa(A)} & \multirow{2}{*}{P1 aGa(A)} & \multirow{2}{*}{B} & \multirow{2}{*}{P1 aGa(B)} \\  & & Gum (Ga) & & & & & Ochre & C & P1 aGa(C) \\ \cline{3-8}  & & & & & & & & \\ \cline{3-8}  & & & & & & & & \\ \hline \multirow{6}{*}{P2} & \multirow{6}{*}{Vermilion (v)} & Animal & \multirow{2}{*}{A} & \multirow{2}{*}{P2 vCa(A)} & \multirow{2}{*}{P2 vCa(A)} & \multirow{2}{*}{C} & \multirow{2}{*}{P2 vCa(C)} \\  & & Glue (Ca) & & & & & & \\ \cline{3-8}  & & & & & & & & \\ \cline{3-8}  & & & & & & & & \\ \cline{3-8}  & & & & & & & & \\ \cline{3-8}  & & & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Description of simulating Hispano-Muslim plaster samples.