*3.4. XRF Analysis*

One of the porcelain artifacts, the TH457 bottle, was analyzed by pXRF. This artifact exhibits the most sophisticated decor, and its shape is well-suited for XRF analysis using a portable instrument since the analyzed area must be roughly perpendicular to the instrument [18]. Additionally, the distance between the instrument and the artifact must be small (~10 mm), and flat areas are required. Figures 14 and 15 show the representative XRF spectra recorded on the white glaze and the different

overglaze enamels (white, blue, green, red, yellow, pink and black) in the 1–22 keV range, where most of the peaks characteristic of major and minor elements were observed. Figure 15 shows details of the 24–30 keV range, where peaks of tin and antimony elements could be compared visually.

As expected for porcelains, the glaze showed elements characteristic of a glassy aluminosilicate porcelain glaze fired at a high temperature [1–3,28–31] with high levels of potassium, calcium and silicon (Table 4). Significant iron content was also obvious in the (colorless) glaze. The high whiteness of the glaze, in association with some iron impurities, demonstrated a firing process under a reducing atmosphere that imposed Fe2<sup>+</sup> speciation. These ions lead to a weak blue coloration, reinforcing the "whiteness" of the glaze for human eyes. Strontium, an impurity of calcium, was detected at a significant level. Light elements such as sodium could not be detected due to their low atomic number. All overglaze enamels were lead-rich: all the Lα, Lα, L<sup>α</sup> XRF transitions of the lead element were clearly observed. A comparison between the relative intensity of lead and potassium or calcium peaks indicated the lower content of lead in the black enamels.


**Table 4.** The glaze and overglaze painted enamels analyzed by pXRF. (**Major**-minor-*traces*).

The XRF spectrum of the blue overglaze enamel showed strong lead peaks; pronounced arsenic, iron and cobalt peaks; and weak manganese and nickel peaks. Arsenic was also observed in the white overglaze enamel (flower decor) as well as in the pink one. Arsenic content is visually detected by the small As K<sup>β</sup> peak just before the Pb L<sup>α</sup> one, the As K<sup>α</sup> peak being at the same position as the strong Pb L<sup>α</sup> one. Confirmation was carried out with the software fitting. Note the high intensity of the potassium peak in blue, according to the use of smalt. The presence of nickel and manganese was due to the impurities found in the cobalt ore used (Table 4). The intensity of the iron peak was rather similar for all overglaze enamels. The presence of manganese was thus consistent with the implication that Asian and European cobalt ingredients were mixed. The detection of arsenic was also significant in relation to the type of the cobalt ore. The red overglaze enamel displayed significant iron peaks, in accordance with the Raman identification of hematite (Figure 7A). Minor amounts of titanium and traces of manganese were also observed, possibly coming from the hematite source. The pink overglaze enamel displayed minor amounts of iron, also indicating the use of hematite. In addition to that, the detection of gold traces was significant, confirming the use of colloidal gold for obtaining the desired hue. The presence of arsenic was also in accordance with the use of Perrot's technique.

The yellow overglaze enamel showed distinct peaks of iron together with minor amounts of antimony and tin, indicating the use of a complex (Fe) Sb-rich Naples yellow lead pyrochlore pigment (see Section 3.2). A similar type of this pigment also seemed to have been used for the green overglaze enamel, with a higher amount of tin and some zinc. Antimony was detected in the low-energy range, but a magnification of the 24–30 keV range (Figure 15) showed the variable content of tin and antimony elements more clearly. The green enamel additionally included copper, which contributes to color formation, together with manganese, nickel and zinc. It was difficult to see if cobalt was also present.

Iron was clearly observed in the black overglaze enameled areas (Table 4). Black enamel was obviously obtained with a mixture of iron and manganese in the presence of copper (and cobalt?), according to the Raman identification of manganese-rich oxide (spinels) (see e.g., Figure 6B(dd') (R1048), Figure 8A(e) (R1175), Figure 9A(e,e',e") (R1006) and Figure 10B(c',c") (TH487)). It is important to note that relative intensities of lead and silicon elements measured on the black lines were intermediate between those measured on other overglaze enamels and that of the glaze. This is due to the limited thickness of the black lines: the XRF spectrum (Figure 15) both displayed the contribution of the black line plus those of adjacent areas, the glaze on one side and the colored overglaze on the other side. All the data obtained by pXRF were in perfect agreement with the Raman data.
