## 6 Results
For the Ti-normalized dataset, PC1 (principal component 1) represented 38.90% of the total variance and allowed us to distinguish between high-Ca and low-Ca pastes, as well as between more weathered items (such as Rb-rich kaolinized intrusives, or shales). On the other hand, PC2 represented 15.24% of the total variance and was influenced by the presence of Cr- and Ni-bearing mineral phases. The log10 statistical dataset, where PC1 and PC2 described 37.47% and 24.42% of the total variance, respectively, provided a better grouping of the samples. Contrary to Ti-normalized dataset, PC1 and PC2 are herein described by the nature of the mineral inclusions and the nature of the clay, respectively. From both the Ti-normalized and log10 PCAs it was possible to easily distinguish between the pastes from Donoratico from those of the internal areas (Monterotondo Marittimo and Roccastrada), where the main discriminant in represented by the use of a different temper in association with more or less calcareous clays. Due to the calcareous/dolomitic nature of the clays that were used for glazed ware pastes, the samples belonging to the EXT group represented the more calcareous terms of the series, but they could not be discriminated from local high-Ca pastes. Once the main features of the reference samples were defined, the statistical analysis was then extended to the whole repertory to investigate the chemical variance of the samples from Vetricella. Four components were extracted that represented 79.91% and 80.19% of the total variance of Ti-normalized and Log10 data, respectively. Biplots of the two first components of each PCA are shown in Figure 6c,d. PC1 and PC2 represented, respectively, 32.35-29.91% and 36.02-20.74% of the total variance for Ti-normalized and log10 PCAs, respectively. The PCA analysis of the whole repertory showed the highly heterogenous nature of the ceramic assemblage from Vetricella, with data superimposed on the groups that were identified by the reference samples. The petrographic analysis of the samples also provided a better assessment of the variations due to temper-related issues. The combined use of PCA and petrographic analysis indicated a large incidence of Roccastrada pastes among the Vetricella fabrics (67%), while Monterotondo Marittimo (19%), Donoratico (10%) and extra-regional (4%) pastes were less represented. The incidence of the different ceramic functional classes or shapes within the Vetricella assemblage is reported in Figure 7a. If the results from the petrographic and chemical analysis are considered, the samples belonging to the Roccastrada ateliers consisted of small amphoteric (55%), likely used for the transportation of goods (so-called small transport amphorae, or STA), cooking ware (23%) and table and storage ware (21%). On the contrary, the samples with a geochemical and mineralogical association with the Monterotondo Marittimo area showed a higher incidence of table and storage ware (50%), together with minor amounts of STAs (38%) and cooking ware (13%). Finally, glazed ware represented the only ceramic class representative of the Donoratico region and extra-regional production (Figure 7b). Figure 6: Bivariate plots from the PCA analysis of the Ti-normalized and log10 datasets relative to: (**a,b**) the reference ceramic samples; and (**c,d**) the whole repertory.