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Historical lime mortars provide valuable information on the construction phases of buildings and allow reconstruction of the chronology of the historical structures. The City Wall of Burgos and the Mudejar Arch of San Martin were declared an Asset of Cultural Interest and have been protected since 1949. Several restorations at the end of the 20th century altered the original appearance of the wall and the current gate, making it difficult to establish stratigraphic relationships between the two structures. Given the scarcity of information on the construction phases of the wall and the uncertainty of the historical dates, a mineralogical and chemical characterization of the mortars was carried out, and the suitability of the binder for radiocarbon dating was assessed. The petrographic, mineralogical and chemical analyses of the lime mortars from the Arc of San Matin show distinctive characteristics, suggesting different construction periods and production processes, where the selection of raw materials and production methods was conducted according to the construction requirements. Moreover, the presence of contaminant phases and microparticles of charcoal in the binder fraction led to discard all the samples for mortar radiocarbon dating. [ABSTRACT FROM AUTHOR]

Sixteen glazes on medieval (14th–16th century AD) pottery fragments from Vega pottery workshop (Burgos, Spain) were characterized to investigate the production technology. To this end, Raman spectroscopy and scanning electron microscopy coupled with energy dispersive X‐ray spectroscopy (SEM‐EDX) were used. The studied glaze samples correspond to fragments of high‐quality glazed ware used by the wealthiest society in the city of Burgos. The most representative types of glazes, corresponding to honey‐marble, honey‐yellow, bright light green, and dark green types, were analysed. Raman spectroscopy shows lead was used as a fluxing agent in glaze production. SEM‐EDX analysis confirms the use of lead oxide and evidences that most of the samples underwent at least two firing processes. No Raman signals of crystalline phases were detected on either glaze surfaces or glaze thin‐sections. The exception is the single firing of dark green glazes, which show pseudobrookite and rutile at the clay body/glaze interface measured in thin section. No colouring crystalline phases were identified by Raman spectroscopy either. However, SEM‐EDX shows iron was the most‐used colouring agent whereas copper was used for bright light green glazes. The polymerization index (Ip) values were used to estimate the firing temperatures. The polymerization index values are typically low for lead glazes and indicate firing temperatures below 700°C. [ABSTRACT FROM AUTHOR]

Here we report a detailed archaeomagnetic and rock-magnetic study of a pottery kiln from Burgos (Spain) to reconstruct its burning conditions and date its last use and abandonment age. During the course of a rescue archaeological excavation carried out in 2015 in the center of Burgos city, a medieval pottery workshop was discovered. Two well-preserved kilns appeared and archaeomagnetic analyses were performed on one of them. In addition to a large amount of pottery remains, some numismatic and documental evidences provided a general chronological estimation, but the abandonment age of the workshop remains unknown. On the basis of the existing archaeological information we carried out an archaeomagnetic study in order to date its last use. 69 archaeomagnetic samples were collected from the combustion chamber and the kiln's fire tunnel. Stepwise alternating field and thermal demagnetization of the natural remanent magnetization (NRM) were carried out to retrieve the mean direction. Additional experiments consisted in the acquisition of isothermal remanence (IRM), low-field magnetic susceptibility and its anisotropy as well as thermomagnetic curves. Despite the high temperatures expected in the combustion chamber, it appeared that the bricks´ samples from the fire tunnel exhibit the most successful directional results. Magnetite and variable contributions of hematite are the main ferromagnetic minerals observed in the thermomagnetic curves. The type of lithology studied, its previous magnetic history and their location in the kiln strongly condition the observed directional and rock-magnetic results. Additionally, AMS data revealed the manufacturing fabric of the fire tunnel's bricks, showing moderately high anisotropy degrees, but not enough to casts doubts on the directional NRM record. In order to test the reproducibility of the dating results, archaeomagnetic dating was carried out using different geomagnetic field models and the Iberian paleosecular variation curve. The small differences observed in the dating results are mainly due to the density and type of input data of these records. The combination of the archaeomagnetic analyses with the archaeological and documental suggests that last kiln's usage took place during the first half of the XVIth century CE. Overall, this paper illustrates how the combination of archaeological data and archaeomagnetic analyses may improve our understanding about the manufacturing processes, use and age of abandonment of archaeological combustion structures. • An archaeomagnetic study of a kiln from the Vega's pottery workshop (Burgos, Spain) is reported here. • Different types of materials from distinct parts of the kiln have been sampled for that aim. • Thermal variation, type of material and its history before being part of the structure condition the magnetic signature. • Archaeomagnetic, archaeological and documental evidences indicate that kiln's last use took place between 1503 and 1545 CE. [ABSTRACT FROM AUTHOR]