## 2 Materials and Methods  
Nearly one hundred ceramic fragments, dating to the 11 th century CE from archaeological sites in Albarracin [3], all of them decorated, were chosen to carry out the study, although only the results of glazed pottery are discussed in this paper. Most of them belonged to the tableware group (bowls, beakers, and dishes). According to their decoration, the studied samples can be classified in four groups:  
* _Cuerda seca_ (Figure 2a): ten fragments were studied, decorated only on the main side of the ceramic;
* White tin-opacified glazes (Figure 2(b1,b2)): twenty-two samples with green and brown-black designs on white glazes (Figure 2(b1)) of the main object side were studied. The secondary sides were coated with yellow glazes (Figure 2(b2));
* Yellow/honey glazes (Figure 2(c1,c2)): almost all the ceramics covered with yellow glazes were coated on both sides with the same color. Sometimes these fragments were decorated with green (Figure 2(c1)) or brown lines (Figure 2(c2)) on the yellow glaze. This type of decoration was very frequent, with a great range of colors among the clay bodies. Twenty-two fragments were chosen for the study;
* Green glazes (Figure 2d): fragments decorated with green glazes included ceramics glazed on both sides, with the same green color in many cases, but some fragments had the main side colored in green and the secondary side of yellow color. Nineteen green glazed samples were selected.  
Chemical analysis of major and minor elements of the ceramic bodies was carried out in a Thermo Elemental Iris Intrepid Radial Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES) (Thermo, Bremen, Germany). Powdered samples were extracted  
Figure 2: Ceramic fragments with different decorations found in Albarracin: (**a**) _Cuerda seca_; (**b1**) White tin-opacified glaze; (**b2**) Yellow gaze on secondary-side of white-tin opacified ceramic; (**c1**) Yellow/honey glaze with green line; (**c2**) Yellow/honey glaze with brown line;(**d**) Green glaze.  
from ceramic bodies by drilling in freshly fractured surfaces of the sherds, using a diamond-tip drill. Samples (50 mg) were digested in open Teflon-vessels. The procedure consisted of successive additions of HNO\({}_{3}\) + HCl, and HF, and a final addition of HNO\({}_{3}\) + HClO\({}_{4}\), heating in every step [8]. After dissolution, every sample was diluted in a 50 mL volumetric flask. For ICP-OES analysis, an 1150 W RF power was used. The following components were determined: Na, Mg, Al, K, and Ca as major elements, and Ti, Mn, Fe, Ba, and Sr as minor elements. Results were submitted to a multivariate statistical treatment by hierarchical clustering analysis (using XLSTAT software, version 2021.2.2).  
Small fragments of glazed ceramics were cut perpendicularly to the glaze-body interface to prepare polished cross-sections in order to examine them by Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). Cross-sections of samples were observed by means of OM, using a Nikon Eclipse 50 ipol (Nikon, Melville, NY, USA). For the determination of glaze composition, a JSM 6360 LV SEM (JEOL, Tokyo, Japan) equipped with an energy-dispersive X-ray analysis (EDS, Inca software, Oxford Instrument, Oxford, UK) with ZAF correction was used, applying an acceleration voltage of 20 kV (oxygen was not measured, oxides were calculated by stoichiometry). The cross-sections were previously carbon coated. X-ray analyses were carried out by scanning large areas of the glaze matrix (normally using \(\times\)2000 magnification, although sometimes \(\times\)5000 magnification was used where the decoration layer was very thin) and acquiring data from ten different points in every sample.  
A Perkin Elmer SCIEX Elan 6000 Inductively Coupled Plasma-Quadrupole Mass Spectrometer (ICP-QMS) (Perkin Elmer, Ontario, Canada), equipped with a cross-flow nebulizer, was used to measure lead isotope ratios in glazes [9]. The measured masses were 204, 206, 207, 208, and 202 to avoid \({}^{204}\)Hg interferences.