412 Documenta Praehistorica LI (2024) DOI: 10.4312/dp.51.19 eo logical structures such as pottery kilns in the area that could contribute to the understanding of firing techniques during this period, an alternative approach to the investigation is required. This paper presents the results of an investigation that sought to identify indirect evidence for Late Bronze and Early Iron Age firing practices in western Slovenia. Introduction Archaeological research has yielded compelling evi- dence for pottery firing techniques during the Late Bronze and Early Iron Ages in western Slovenia. These resulted from Fourier Transform Infrared Reflectance Spectroscopy (FTIR) analysis conducted on ceramic sam ples obtained through archaeological experiments and archaeological excavations. As there are no ar cha- KLJUÈNE BESEDE – keramika; tehnike žganja keramike; eksperimentalna arheologija; petrografska ana liza; FTIR - infrardeèa spektroskopija s Fourierovo transformacijo; Kras; Slovenija IZVLEÈEK – Študija je usmerjena v analizo tehnik žganja keramike v pozni bronasti in starejši železni dobi na Krasu v Sloveniji. Zaradi odsotnosti arheološki struktur smo uporabili alternativni razisko val - ni pristop, in sicer FTIR in keramiène petrografske analize. Arheološki material smo analizirali s po- moè jo modela, ki smo ga razvili pri arheološkem raziskovalnem delu, žganju v jami in žganju v peèi. S pomoèjo raziskave smo uspešno prepoznali razliène tehnike žganja, ki so bile v uporabi v pozni bronas- ti in starejši železni dobi. Raziskovanje tehnik žganja keramike v zahodni Sloveniji v pozni bronasti in starejši železni dobi na podlagi FTIR in petrografskih analiz KEY WORDS – pottery; firing techniques; experimental archaeology; petrographic analysis; FTIR - Fouri- er Transform Infrared Spectroscopy analysis; Karst; Slovenia ABSTRACT - This study focuses on the analysis of pottery firing techniques during the Late Bronze and Early Iron Ages in the Karst region of Slovenia. Given the absence of archaeological structures, we adopt - ed an alternative research approach, employing FTIR and ceramic thin-section analysis. The archaeolo- gical material underwent study using a model derived from archaeological experiments, which encom- passed firing techniques in both pits and pottery kilns. Our research successfully identified that various firing structures were utilized during the Late Bronze and Early Iron Ages. Manca Vinazza1, Petros Chatzimpaloglou2 1 Department of Archaeology, Faculty of Arts, University of Ljubljana, Ljubljana, SI; manca.vinazza@ff.uni-lj.si 2 McDonald Institute for Archaeological Research, University of Cambridge, UK; pc529@cam.ac.uk Investigating the pottery firing techniques in western Slovenia during the Late Bronze and Early Iron Ages using FTIR and petrographic analysis 413 Investigating the pottery firing techniques in western Slovenia during the Late Bronze and Early Iron Ages ... The existing knowledge of pottery technology and pro- duction during this period in the study area derives from limited research, primarily from a macroscopic point of view and focusing solely on settlement ma te- rial, such as storage, cooking, and serving types of ves - sels. The pottery is locally produced and hand made, fired in bonfires/pit-fires and single-chamber kilns. Typological analysis indicates a clear influence from the west, particularly from the Veneto and Friuli re- gions in northern Italy. The application of the Fourier Transform Infrared Re - flectance Spectroscopy (FTIR) has been proven as an excellent method for identifying the mineralogical com - position of archaeological ceramics and estimating firing temperatures (Shoval, Paz 2015; Shoval 2016). Such information can contribute significantly to the reconstruction of firing structures and to a more nu anc - ed comprehension of firing techniques. This re search comprises an interdisciplinary study of ce ra mics from two hillforts: (a) the Tabor site, span ning the Late Bronze to Early Iron Age, situated near Vrabèe, and (b) the Štanjel site, representative of the Early Iron Age site (Fig. 1). In addition to the aforementioned FTIR analyses, cera - mic petrographic thin-section analyses were conducted on ceramic materials procured from both sites, fo cus- ing on forms presumed to be of local production. The va lidation of local pottery production serves to draw conclusions about the firing structures in the exa min- ed area. Furthermore, an archaeological experiment-based mo - del was built to facilitate the comparison with the ar chaeological material. This involved the recreation of probable firing techniques and conditions from the Late Bronze and Early Iron Ages, accomplished through the construction of a one-chamber kiln and the replication of vessels using local clays. Archaeological background The prehistoric Karst Plateau The Karst Plateau is a landscape between the Gulf of Trieste and the Vipava Valley. In the northwest, it is connected with the Soèa Plain, in the southwest with the Brkini Hills, the Podgorje Karst Plateau with the Èièarija Plateau, and the Podgraje Lowland (Perko, Klad nik 1998). The Karst Plateau is famous for the so- called hillforts (sl. gradišèa, it. castellieri), which are dated to the Bronze and/or Early Iron Ages (Mar che - setti 1903). Most of these hillforts were poorly ex ca - vated and the stratigraphy was preserved only in a few cases (Canarella 1975–1977; Moretti 1978; Nova- ko viæ, Turk 1991; Bratina 2014; 2021; Zupanèiè, Vi- naz za 2015; Maggi et al. 2017; Borgna et al. 2018; Ber - nardini et al. 2023). The archaeological material under consideration was collected from two hillforts, Tabor near Vrabèe and Štanjel. The chro nological framework for both sites was es tab lished through stratigraphic analysis, and con firmed by both archaeological evidence and abso - lute data (Vinazza 2021.Fig. 5). The Tabor near Vrabèe site with a double dry-wall has two occupational phases. The ini tial phase is dated to the end of the Late Bronze Age (10th century BC), while the second cor- responds to the Early Iron Age (8th and 7th centuries BC). In contrast, the Štanjel site contains the foun da- tions of a cellar dug into the limestone bedrock, dating to the conclusion of the end of the Early Iron Age (6th and 5th centuries BC) (Vinaz za 2021.429,442, Fig. 5). Pottery firing in the Late Bronze and Early Iron Ages in Slovenia The first archaeometric study about Bronze and Iron Age firing techniques on Slovenian pottery was con- ducted in 2021 (Vinazza, Dolenec 2021). Existing re - search in Slovenia has been limited to individual ar- chaeological sites, as evidenced by studies such as Ja - nez Dular (1982), Matija Èrešnar (2006), Andreja Ži b - rat Gašpariè et al. (2018), with macroscopic ana lysis of ceramic technology still dominating the lite rature. Since we are dealing with both direct and indi rect data pertaining to pottery firing at this time in Slove nia, a com prehensive understanding is possible through an overview of the current state of research. Macroscopic and microscopic examinations of pottery technologies, constituting indirect data, suggest the utilization of both bonfires/pit fires and kilns. Notable examples include the Poštela and Novine sites in north- eastern Slovenia, as well Štanjel, Tabor near Vrabèe, and Tomaj in the Karst region (Žibrat, Dolenec 2015; Žib rat et al. 2018.188; Vinazza, Dolenec 2021.401; Vi - nazza 2022). Meanwhile, only a limited number of archaeologically ex cavated kilns, serving as direct data, have been iden - tified for pottery production. Regardless of the type, these kilns are predominantly of the one-chamber type, as documented by Irena Horvat Šavel (1988–1989. 130–131) and Draško Josipoviæ et al. (2016). Although 414 Manca Vinazza, Petros Chatzimpaloglou archaeological material can effectively dif ferentiate between pottery fired in a bonfire/pit fire and that fired in a kiln. Geological background of the Karst Plateau The Karst Plateau is a flat plain with conical hills, small elevations, denuded karst areas, sinkholes, caves and the average altitude above sea level is 300 to 600 me - tres above sea level. Despite the absence of sur face streams, the plateau harbours a significant under- ground stream system, one that gathers available wa - ter and directs it towards the spring of Timav (Jur kov- šek et al. 1996.21). Tabor near Vrabèe The archaeological site of Tabor near Vrabèe (Fig. 2) encompasses two main li tho stratigraphic units: the Lipica For ma tion and the Flysch. The Lipica Formation locally contains the Tomaj limestone, a platy and la mi- nated li mestone with chert. The limestone is bedded and massive with rudist biostromes and bio herms (Jur kovšek et al. 1996.25, App.). Cherts occur in the Tomaj limestone as nodules and thin lenses and have a micro cry stalline texture (Jurkovšek et al. 1996.47). The Flysch unit results from the alteration of marl, sandy silt stone and coarse-grained carbonate sand- stone, with inter ca lations of breccia and conglo me rate, which consist mainly of fragments and peb bles of old- er car bo nate platform formation. The brec cia and con- glo merate varieties encompass basalt conglomerate and calcite-ce ment ed breccia, featuring limestone frag- ments of di verse sizes (Jurkovšek et al. 1996.63). Štanjel The archaeological site of Štanjel lies in an even more dynamic area (Fig. 2), between four lithostratigraphic units: the Lipica Formation, the Flysch, the Liburnian Formation, the Lower Trstelj, and the Upper Trstelj beds. The Liburnian Formation comprises marly lime- stone and limestone breccia, while the Upper Trstelj beds, which primarily consist of miliolid limestone, exhibit calcarenite with foraminifers and Coral-algal limestone (Jurkovšek 2010.27,40). Clays Fieldwork in the wider area of interest identified va ri - ous clay sources potentially suitable for pottery pro- duction. The selection of clays focused on proximity to archaeological sites (i.e. Tabor near Vrabèe and Šta- njel) and suitability for pottery production. Therefore, samples were collected from the Renèe source in the the two-chamber kiln, excavated archaeologically, is dated to the Late Iron Age (Tomaniè Jevremov, Guštin 1996), evidence from neighbouring northern Italian sites suggests its use in the Late Bronze Age (Levi 2010. 117), but most examples of such kilns are known from the Early Iron Age (Poggiani Keller 1994.76; Iaia, Moroni Lanfredini 2009.65,68,70; Gasparini, Miari 2017.24; Rapi et al. 2019.107). The absence of archaeologically excavated kilns is notable at the Late Bronze and Early Iron Age sites in the Karst, yet indirect data allude to their probable exi- stence (see Vinazza 2021; Vinazza, Dolenec 2022). Moreover, an analysis of the chaíne opératoire of cer - tain locally produced vessel types, exemplified by the ceramic situlae from the Štanjel site, suggests the use of two-chamber kilns. This specific pottery requires an oxidation-reduction-oxidation (ORO) firing at mo- sphere, achievable only in such kilns. By analysing the provenance based on petrographic thin-section ana ly- sis we can distinguish between local and non-local pro - duction and foresee the use of this kind of firing tech- nique in the area under study. This research aims to compare the firing model derived from ar chaeological experiments using FTIR analyses, which is based on temperature estimation. Additionally, the study seeks to ascertain whether the results of FTIR ana lyses of Fig. 1. A map showing the location of the clay sources (1 Renèe, 2 Ostri vrh, 4 Veliki Dul, 5 Gri že) and the ar cha eo logical sites (3 Štanjel, 6 Ta bor near Vrabèe). Source: https://maps-for-free.com/ 415 Investigating the pottery firing techniques in western Slovenia during the Late Bronze and Early Iron Ages ... fired in a replicated one-chamber kiln, in a pit fire and an electric laboratory kiln. Archaeological pottery was sampled from two sites, Tabor near Vrabèe and Štanjel, from which we ob- tained stratified material with absolute 14C dates. We selected material that we were confident was locally produced, including storage and cooking vessels, as well as a locally made ceramic situla fired in ORO con- ditions. We sampled local clay sources in the vicinity of both archaeological sites: Griže near Tabor, and Veliki Dul and Ostri vrh near Štanjel. Furthermore, the experimental pottery served for com parisons with archaeological pottery. To achieve this, samples from both the experimental and ar cha eo- logical pottery were taken and analysed through FTIR spectroscopy (Parish et al. 2013) and petrographic study of ceramic thin sections (Quinn 2022). Additio - nal ly, the findings from these techniques were com ple- Fig. 2. Geological map of the area under our study (modified after Jurkovšek 2013). Vipava Valley, the Ostri vrh, and Veliki Dul near the Šta - njel site, and the Griže source near Tabor (Fig. 1). All sampled localities are classified as rendzina soils on limestone, with an initial cambic horizon (Vidic et al. 2015.48). The Renèe clay, gathered from a clay mine in the Vipava Valley, is identified as the illite-chlo rite type, featuring a grey to brown upper layer compris - ing a medium to well-laminated clay with an ave rage thickness of 5m. The mineral com position encompas- ses chlorite, quartz, albite, montmorillonite, carbonate, and iron minerals (Ro kavec 2014.32,35,54). Clays from Ostri vrh and Griže were collected on the hill- sides, while the samples from Veliki Dul were collected in a valley (Fig. 1). They fall under the terra rossa type (Šušteršiè et al. 2009.Tab. 1). Materials and methods Archaeological experiments, as detailed in Manca Vi- nazza (2021a; 2021b.183–184) and Vinazza and Matej Dolenec (2022.392), were conducted in the courtyard of the De partment of Archaeology at the University of Ljubljana in the years 2020 and 2021. The initial phase involved the construction of a one-chamber kiln, uti- lizing Renèe clay. Subsequently, ceramic vessels were made from the examined clay sources, which were 416 Manca Vinazza, Petros Chatzimpaloglou process carbon dioxide (CO2) is released from the mi- neral’s structure and free-lime (CaO) is formed (Fabbri et al. 2014). The decarbonation of calcite in ceramics takes place under prolonged firing at temperatures between 600 and 800°C (Mag getti et al. 2011). After long-lasting high firing temperatures (800°C and above), part of the free-lime is re-carbonated and cry - stallized as reformed calcite (Shoval et al. 2011b; Fab- bri et al. 2014). The presence of a calcareous (calcite- rich) component in the raw ma terial is very important since it greatly affects the thermal reactions and the firing process (Fabbri et al. 2014; Shoval 2016). Petro thin-section analysis Petrographic analysis took place at the Laboratory for Material Analysis Laboratory within the Department of Archaeology at the University of Ljubljana. The pre - paration of ceramic thin sections adhered to a stan- dard protocol (see Quinn 2022.23–36), and the exa mi - nation was conducted under the polarizing Zeiss Axio Scope A1 microscope. Three distinct groups of ceramic material were chosen. The first is associated with the Renèe clay source (Samples 1, 2, 5 and 7). The se cond group is linked with the Tabor near Vrabèe site (Sam- ples 11 and 18), while the third pertains to the Štanjel site (Sam ples 9 and 13). Archaeological experiments The experimental kiln was made of Renèe clay that was tempered with straw. After the completion of the ex- periment, samples were collected from the base (Sam- ple 2), the chimney (Sample 3), and the wall (Sample 4), which was taken 10cm above second thermocouple. During the experiment two thermocouples were placed at the base of the kiln, one under the fired ves- sels and the other adjacent to the wall (see Vinazza, Dolenec 2021.Fig. 3). The tem perature measured with the thermocouples in the experimental kiln was 670°C. Several pots were fired in the experimental kiln, including Sample 1, modelled from Renèe clay; Sample 10 modelled from Veliki Dul clay; and Sample 11 modelled from Griže clay. All of these pots were tem pered with calcite. In accordance with recent research by Richard Thèr et al. (2018), which proposed a model for distinguishing firing structures based on soaking time duration, we conducted experiments firing two clay cubes (5x5x 5cm) from Renèe clay in a laboratory kiln. The first cube (Samples 5 and 6) was fired at 600°C, while the se cond cube (Samples 7 and 8) was fired at 800°C. mented by previously acquired X-ray Diffraction (XRD) results (see Tab. 1). FTIR Spectroscopy The FTIR equipment employed for this research was located in the Charles McBurney Laboratory for Geo- archaeology, based in the Department of Ar chaeology at the University of Cambridge. Representative FTIR spectra were obtained from all the clay and ceramic samples (n=21) by grinding a few tens of micrograms of the sample using an agate mortar and pestle (Smith 2011). About 0.1mg or less of the sample was mixed with about 80mg of KBr (IR-grade). A 7mm pellet was then made using a hand press and the spectra were col - lected between 4000 and 400cm–1 at 4cm–1 reso lu - tion, using a Thermo Nicolet 380 spectrometer. The in - terpretation of the spectra was conducted by combin - ing the internal library of infrared spectra of archaeo- lo gical materials (Kimmel Standards) and the appro- pri ate reference (Weiner 2010; Chukanov 2014; Sho- val, Paz 2015; Shoval 2016). Ceramics are produced by firing clay raw materials, which during this process undergo a series of reactions and transform into the final product. Using the FITR technique the main components of this final product can be identified (Weiner 2010; Chukanov 2014). This allows us to determine what was the original com po - sition of the raw material and estimate the firing tem- peratures of this process (Sho val, Paz 2015; Shoval 2016). The most common components reported in ar- chaeological pottery/ceramics are clay minerals (e.g., kaolinite, smectite), quartz and calcite, and they are re- cognized on the FTIR spectra by specific bands (Tab. 1). The raw clay component transforms through firing to fired-clay, also defined as meta-clay (Shoval et al. 2011a; 2011b). The transformation occurs over a pro - cess called dehydroxylation during which the raw clay loses the water (H2O) from its structure. De pend ing on the type of clay, this process takes place at dif fe rent temperatures and subsequently forms different meta- clay components (Shoval et al. 2011a; 2011b; Shoval, Paz 2015). A clay material do minated by kaolinite trans forms into meta-kaolinite and the dehydroxy la - tion occurs at 450–500°C (Frost, Vassallo 1996). A clay material dominated by smectite transforms into meta- smectite and this transformation occurs at c. 600°C (Heller-Kallai, Rozenson 1980). Meanwhile, calcite decomposes through a thermal pro - cess called decarbonation (Shoval 2016). During this 417 Investigating the pottery firing techniques in western Slovenia during the Late Bronze and Early Iron Ages ... Sa m - pl e La b ID IT EM De sc rip tio n Fi rin g st ru ct ur e Cl ay Te m - pe r Fi rin g st ru ct ur e M ax i- m um O th er 1 20 22 -2 Ve ss el Ri m o f t he b ow l Ar ch ae ol og ic al e xp er im en t Re nč e Ca lc ite Re pl ic a of th e ki ln 67 0 °C XR D (V in az za , D ol en ec 2 02 2. Sa m pl e 2 ) 2 20 22 -3 Ki ln Bo tto m o f t he k iln Ar ch ae ol og ic al e xp er im en t Re nč e St ra w Re pl ic a of th e ki ln 67 0 °C XR D (V in az za , D ol en ec 2 02 2. Sa m pl e 3 ) 3 Ki ln Ch im ne y of th e ki ln Ar ch ae ol og ic al e xp er im en t Re nč e St ra w Re pl ic a of th e ki ln 67 0 °C XR D (V in az za , D ol en ec 2 02 2. Sa m pl e 5 ) 4 20 21 -4 Ki ln W al l o f t he k iln Ar ch ae ol og ic al e xp er im en t Re nč e St ra w Re pl ic a of th e ki ln 67 0 °C XR D (V in az za , D ol en ec 2 02 2. Sa m pl e 4 ) 5 20 22 -2 3 Cu be Co re La bo ra to ry fi rin g Re nč e 0 El ec tr ic al ly o pe ra te d ki ln 60 0 °C XR D (V in az za , D ol en ec 2 02 2. Sa m pl e 6 ) 6 20 22 -2 3 Cu be O ut er su rf ac e La bo ra to ry fi rin g Re nč e 0 El ec tr ic al ly o pe ra te d ki ln 60 0 °C XR D (V in az za , D ol en ec 2 02 2. Sa m pl e 6 ) 7 20 22 -2 4 Cu be Co re La bo ra to ry fi rin g Re nč e 0 El ec tr ic al ly o pe ra te d ki ln 80 0 °C XR D (V in az za , D ol en ec 2 02 2. Sa m pl e 7 ) 8 20 22 -2 4 Cu be O ut er su rf ac e La bo ra to ry fi rin g Re nč e 0 El ec tr ic al ly o pe ra te d ki ln 80 0 °C XR D (V in az za , D ol en ec 2 02 2. Sa m pl e 7 ) 9 20 22 -4 Si lo Št an je l s ite , U S 28 Ar ch ae ol og ic al p ott er y 10 20 20 -1 8 Ve ss el Pa rt o f t he v es se l Ar ch ae ol og ic al e xp er im en t Ve lik i Du l Ca lc ite Re pl ic a of th e ki ln 67 0 °C 11 20 20 -2 4 Ve ss el Pa rt o f t he v es se l Ar ch ae ol og ic al e xp er im en t Gr iže Ca lc ite Re pl ic a of th e ki ln 67 0 °C 12 Ve ss el Pa rt o f t he v es se l Ar ch ae ol og ic al e xp er im en t Re nč e Ca lc ite Pi t fi re 70 2 °C 13 20 22 -1 Si tu la Št an je l s ite , U S 28 Ar ch ae ol og ic al p ott er y 14 Cl ay N o m an ip ul ati on Re nč e 15 Cl ay N o m an ip ul ati on Ve lik i Du l 16 Cl ay N o m an ip ul ati on Gr iže 17 Cl ay N o m an ip ul ati on O st ri Vr h 18 20 20 -4 Pi th os Ta bo r n ea r V ra bč e sit e, U S 18 , o ut er su rf ac e Ar ch ae ol og ic al p ott er y 19 20 20 -4 Pi th os Ta bo r n ea r V ra bč e sit e, U S 18 , c or e Ar ch ae ol og ic al p ott er y 20 M 34 9 Po t Št an je l s ite , U S 42 , co re ar ch ae ol og ic al p ott er y 21 M 34 9 Po t Št an je l s ite , U S 42 , ou te r s ur fa ce Ar ch ae ol og ic al p ott er y Ta b. 1 . S am pl es 1 –2 1 w hi ch a re p ar t o f o u r st u dy . 418 Manca Vinazza, Petros Chatzimpaloglou nance of this mineral is further supported by the shoul - der band at 913cm–1 and the band at 3620cm–1. The Si-O/Al-O bending mode at 469cm–1 can equally re late to smectite and quartz (Weiner 2010; Kimmel Stan- dards), although research on clay and pottery has as- signed this mode based on the overlap between these two minerals reported in such materials (Shoval 2016). The presence of quartz is confirmed by the cha - racteristic band-doublet at 778 and 798cm–1, and the minor peak at 695cm–1. The spectrum also re corded a shoulder band at 1166cm–1, which is re lated to SiO2 mineral polymorphs (e.g., tridymite, cristo balite, quartz) (Chukanov 2014). Clay materials contain small amounts of water in their mineralogical struc ture and/ or between the layers of these minerals (Wenk, Bulakh 2016; Kumari, Mohan 2021). The pre sence of such wa- ter is detected by the very broad H2O-stretching band at 3422cm–1 and the H2O bending mode at 1637cm–1. The band at 528cm–1 is assigned to kaolinite–mont mo - rillonite based on previous work on this type of clay mi nerals (Chukanov 2014). Montmorillonite, in gene- ral, is the most prominent member of the smec titic group of clay minerals (Kumari, Mohan 2021), and very often interstratifies with other clay minerals (e.g., kaolinite, illite), which further supports its existence in this sample. The band at 528cm–1 could also be related to albite (plagioclase – Na-feldspar) and muscovite (mi - ca mineral), which are minerals commonly found with - in clay materials (Chukanov 2014; Kumari, Mohan 2021). However, the spectrum did not record any of the indicative bands of these minerals, so the likelihood of their presence is low. Veliki Dul clay (App. 5: 15) The spectrum from the Veliki Dul clay source recorded a principal Si-O stretching band at 1032cm–1, which is associated with smectite. The dominance of this mi- neral is supported by the shoulder band at 913cm–1, the bands at 3620cm–1 and 534cm–1, and the minor peak at 3692cm–1. The combined Si-O/Al-O bending mode at 469cm–1 is again considered the result of the overlap between smectite and quartz (Shoval 2016). The presence of quartz is confirmed by the charac te - ris tic band-doublet at 777 and 797cm–1, and the minor peak at 694cm–1. Water, related to the clay com po- nents, is recorded by the very broad H2O-stretching band at 3438cm–1 and the H2O bending mode at 1637cm–1. The band at 534cm–1 could again relate to muscovite or albite, but for the same reasons as with the Renèe sample it is attributed to the kaolinite–mont- mo rillonite. The last experimental sample (Sample 12) was pit fired in 2021, as documented by Vinazza (2021.61, Fig. 1). The firing reached temperatures of 702°C in less than one hour, with a subsequent cooling time lasting two hours and 41 minutes. Archaeological material Archaeological material comes from two sites. Be gin- ning from the Tabor near Vrabèe site, archaeological research (Vinazza 2021.Pl.1:1) established that the pithos (Sample 18, 19) belonged to the first occupation phase (Late Bronze Age). Macroscopic technological analysis data indicated the prevalence of a reduction atmosphere (O.c.432), yet it remains un clear whether the firing technique involved a bonfire/pit fire or a kiln. From the Early Iron Age, we sampled material from the Štanjel site. A silo (Sample 9), was chosen first due to its status as the most diverse material within the site’s assemblages and its local origin. It is presumed that the firing was not conducted in a kiln type (or related) structure. Based on its diameter of up to 100cm and a wall thickness of 5cm, it was believed to have been fired at low temperatures (Vinazza 2016.9,11) in a bon fire. The next archaeological find from the Štanjel site is a ceramic situla (Sample 13), which, based on ma cro- sco pic analysis, is believed to have been fired in a double-chamber kiln, as this type of pottery vessel re- quires an ORO firing (cf. Aloupi-Siotis 2020.3,5). The last vessel from the Štanjel site is a pot (Vinazza 2021.Pl.6: 8) from which samples were taken from the core and outer surface (Samples 20, 21). Results FTIR Spectroscopy The analysed material has been categorized into three main groups. Initially, we examined the raw ma te rials, encompassing analysis of four different clay sources. Sub sequently, the experimental material was inves- tigated, comprising materials collected from both the kiln and pottery. Finally, attention was directed to- wards the archaeological material. Raw material Renèe clay (App. 5: 14) The spectrum from the Renèe clay source recorded a principal Si-O stretching band at 1028cm–1 which is indicative of smectite (Kimmel Standards). The do mi - 419 Investigating the pottery firing techniques in western Slovenia during the Late Bronze and Early Iron Ages ... water (i.e. absorbed water) during a slow rehydration process (Muller et al. 2000; Shoval, Paz 2013). Quartz is identified by the characteristic band-doublet at 779 and 798cm–1, the minor peak at 695cm–1 and the shoul der band at 520cm–1. Last ly, the shoulder band at 1166cm–1 and the weak band at 1870cm–1 are as so ci- ated with SiO2 mineral polymorphs. The presence of the meta-smectite suggests that this ceramic material endured temperatures around 600°C (Heller-Kallai, Rozenson 1980). However, the spec- trum recorded a minor band at 3621cm–1, which is at - tributed to raw smectite (i.e. retains its original struc- ture). This suggests that the firing procedure did not consistently maintain high temperatures (600°C and above) and allowed the preservation of a small raw smectitic component. Meanwhile, the presence of me ta-kaolinite does not support temperatures below 450°C, so the base probably experienced temperatures between 450 and 650°C. Wall (App. 2: 4) The spectrum of the wall sample recorded a principal Si-O stretching band at 1040cm–1 which is indicative of meta-smectite since it falls within the range of 1030– 1060cm–1. Moreover, it presented a shoulder peak at 1085cm–1 that is assigned to the overlap occurring be- tween quartz and meta-kaolinite. The combined Si-O/ Al-O bending mode at 469cm–1 further confirms that meta-clay is the principal component of this sample. Absorbed water, associated with the meta-clay unit, is detected by the H2O-stretching band at 3421cm–1. Quartz is identified by the characteristic band-dou blet at 779 and 798cm–1, and the minor peak at 694cm–1. The spectrum also included a minor band at 1618cm–1 that is related to SiO2 mineral polymorphs. In com pa- rison to the base’s sample, this one has a cal careous com ponent. A main CO3 band at 1437cm–1 and a se- con dary band at 879cm–1 have been recorded, which are characteristic of calcite. Moreover, the spectrum re - corded a minor band at 729cm–1, which is indicative of dolomite. The presence of meta-smectite and the absence of raw smectite suggest that this ceramic material endured high firing temperatures (>600°C). The main CO3 band falls within the range of 1430–1450cm–1, which is associated with reformed calcite (Shoval 2016). The presence of this type of calcite suggests firing tem pe - ratures consistently above 700°C. Meanwhile, the spec- trum did not present bands assigned to ‘firing sili ca - Griže clay (App. 6: 16) The spectrum from the Griže clay source is very similar to those collected from the samples of Renèe clay and Ve liki Dul clay sources. It is dominated by smectite ba- sed on the principal Si-O stretching band (1032cm–1) and the bands at 3693cm–1, 3620cm–1, 915cm–1, and 531cm–1. The combined Si-O/Al-O bending mode at 469cm–1 is regarded as the result of the overlap be- tween smectite and quartz. Clay-related water is re- cord ed by the very broad H2O-stretching band at 3422cm–1 and the H2O bending mode at 1637cm–1. Fur thermore, quartz is identified by the characteristic band-doublet at 777 and 797cm–1 and the minor peak at 695cm–1. The spectrum also included a shoulder band at 1165cm–1 that is related to SiO2 mineral po ly - morphs. Ostri vrh clay (App. 6: 17) The spectrum from the Ostri vrh clay source has many similarities with the ones collected from the other three sources. The principal Si-O stretching band at 1031cm–1 the shoulder band at 913cm–1, the bands at 3620cm–1 and 531cm–1, and the minor peak at 3691 cm–1 indicate the dominance of smectite in this sam- ple. Meanwhile, the combined Si-O/Al-O bending mode at 470cm–1 is again considered the result of the over- lap between smectite and quartz. Clay-related water is again recorded by the H2O-stretching band at 3422 cm–1 and the H2O bending mode at 1637cm–1. Lastly, the presence of quartz is confirmed by the cha rac- teristic band-doublet at 779 and 798cm–1 and the mi- nor peak at 694cm–1. Experimental material (2020) Base (App. 1: 2) The spectrum of the sample collected from the base of the Kiln recorded a principal Si-O stretching band at 1036cm–1 which is associated with a meta-clay (i.e. fired-clay). Considering that this band falls within the range of 1030–1060cm–1, the main component of this sam ple is meta-smectite (Shoval 2016). Besides the main band, the spectrum includes a shoulder band at 1090cm–1, suggesting that this sample also includes me ta-kaolinite. The dominance of meta-clay in this sam ple is further supported by the combined Si-O/Al-O bending mode at 469cm–1, which is also related to the fired-clay material (O.c.). Clay-related water is also detected by the very broad H2O-stretching band at 3422cm–1 and the H2O bend- ing mode at 1636cm–1 (Shoval 2016). The meta-clay ce- ramics, being dehydrated after firing, strongly absolve 420 Manca Vinazza, Petros Chatzimpaloglou racteristic band-doublet at 778 and 797cm–1, and the minor peak at 694cm–1. The spectrum also recorded a minor band at 1618cm–1 and a shoulder band at 1166cm–1 that are both associated with SiO2 mineral polymorphs (Chukanov 2014). Absorbed water, as so - ciated with the meta-clay is detected with the H2O bending mode at 1638cm–1. In contrast, the spectrum did not detect a calcite component in the exa mined sam ple. Meta-kaolinite is formed at 450 to 500°C (Frost, Vassallo 1996) and retains its structure up to 950°C (Shoval 2016; Stevenson, Gurnick 2016). Since no other recorded component can provide fur ther in- formation on the firing temperatures, it is considered that this experimental pot was fired at temperatures between 450 and 900°C. Pot 2 (App. 4: 12), Renèe clay Another pot was made from Renèe clay that was also tempered with calcite but fired in a pit fire. The col lect - ed spectrum recorded a principal Si-O stretching band at 1036cm–1, which is indicative of a meta-smec tite. There is also a shoulder peak at 1085cm–1 which is at - tributed to the overlap between the quartz and the meta-kaolinite component. The dominance of the meta-clay in the sample is supported by the combined Si-O/Al-O bending mode at 473cm–1. Meanwhile, raw smectite is reported by the minor band at 3620cm–1 and a band at 521cm–1. Water as sociated with the clay components (i.e. raw and meta) is detected by the broad H2O-stretching band at 3422cm–1 and the H2O bending mode at 1637cm–1. Quartz is identified by the characteristic band-doublet at 779 and 797cm–1, and the minor peak at 695cm–1. The spectrum also recorded a minor band at 1872cm–1 and a shoulder band at 1164 that are related to SiO2 mineral polymorphs. Furthermore, the spectrum has a main CO3 band at 1420cm–1, a secondary band at 875 cm–1,and minor bands at 1796 and 712cm–1, which are characteristic of primary calcite (Shoval 2016). The reported meta-clays in this sample support firing temperatures between 600°C and 900°C (Shoval 2016; Stevenson, Gurnick 2016; Tarhan, Iºık 2020). How- ever, the occurrence of primary calcite does not jus- tify temperatures that go much higher than 700°C. Moreover, the detected raw clay suggests that the firing procedure did not consistently maintain high temperatures (>600°C). Based on these results, the highest temperatures reached in the pit fire was proba - bly around 700°C, while the average firing tem pera- tures should have been around 600°C. tes’ (i.e. around 912cm–1), which would indicate tem- peratures above 800°C (Shoval 2016). These findings indicate that these walls were exposed to temperatures between 700 and 800°C that led to the complete trans- formation of the main components of the clay material (i.e. clay and calcite). Chimney (App. 1: 3) The spectrum of the chimney sample recorded a prin- cipal Si-O stretching curve that splits into two peaks. The first at 1082cm–1 is generally associated with quartz (Saikia et al. 2008) but in pottery samples it is re garded as the result of the overlap between quartz and meta-kaolinite (Shoval, Paz 2015). Meanwhile, the second peak at 1038cm–1 is indicative of meta-smec- tite. The combined Si-O/Al-O bending mode found at 465cm–1 supports that meta-clay and quartz are the main components of this sample. The considerable presence of quartz, in addition to the Si-O stretching band, is confirmed by the characteristic band-doublet at 778 and 797cm–1, and the minor peak at 694cm–1. Moreover, the minor band at 1618cm–1 and the shoulder band at 1164cm–1 are both associated with SiO2 mineral polymorphs. Absorbed water, as sociat- ed with the meta-clay unit, is detected with the H2O- stre tching band at 3421cm–1 and the H2O bend ing mode at 1637cm–1. Regarding the firing temperature, the presence of me - ta-smectite and the absence of bands attributed to raw smectite suggest that this sample experienced high firing temperatures (>600°C). Meta-kaolinite retains its structure for temperatures up to 950°C (Shoval 2016; Stevenson, Gurnick 2016), while the meta-smec- tite starts to show signs of distortion at temperatures above 900°C (Ste venson, Gurnick 2016; Tarhan, Iºık 2020). Such signs are not recorded in the spectrum, suggesting that this sample was ex posed to tem pera- tures between 600 and 900°C for a sufficient amount of time. Pot 1 (App. 1: 1) (Renèe clay) A pot was made from Renèe clay that was tempered with calcite and fired within the experimental kiln. The FTIR analyses recorded a principal Si-O stretching band at 1082cm–1, which is considered the result of the overlap between the quartz and the meta-kaolinite component (Shoval, Paz 2015). The combined Si-O/ Al-O bending mode at 462cm–1 is also attributed to the overlap between these two components. The impor- tant presence of quartz is further identified by the cha - 421 Investigating the pottery firing techniques in western Slovenia during the Late Bronze and Early Iron Ages ... the previous cube, samples were collected from the core and outer surface, and analysed by FTIR. The core’s spectrum recorded a principal Si-O stretching band at 1082cm–1 which is the result of the overlap be - tween the quartz and a meta- kaolinite. The Si-O asym - metrical bending vibration at 457cm–1 is more compa- tible with quartz rather than a meta-clay. The increased presence of this mineral is further confirmed by the characteristic band-doublet at 778 and 797cm–1, and the minor peak at 694cm–1. The spectrum also re cord- ed minor bands at 1870 and 1618cm–1, and shoulder bands at 1164 and 557cm–1 that are related to SiO2 mineral polymorphs. These findings suggest that SiO2 mineral polymorphs (e.g., quartz) are the dominant component of this cube’s core. Lastly, absorbed water related to the meta-clay component is detected by the H2O-stretching band at 3421cm–1. The outer surface’s spectrum recorded a principal Si-O stretching curve that splits into two peaks. The first is at 1036cm–1 and it is assigned to meta-smectite, while the second peak at 1086cm–1 is the result of the over- lap between the quartz and the meta-kaolinite com- ponent of the sample. The dominance of the meta-clay in this sample is further supported by the combined Si-O/Al-O bending mode at 470cm–1. Absorbed water is detected by the very broad H2O-stretching band at 3421cm–1 and the minor H2O bending mode at 1637 cm–1. Regardless, this sample also holds a strong con- tent of SiO2 mineral polymorphs. Quartz is identified by the characteristic band-doublet at 779 and 797cm–1, and the minor peak at 694cm–1, where other SiO2 polymorphs are detected by the two shoulder bands at 1164cm–1 and 561cm–1. Regarding the firing temperature, the presence of only meta-kaolinite in the core of this pottery cube suggests that it was broadly exposed to temperatures between 450°C and 900°C (Frost, Vassallo 1996; Shoval 2016; Stevenson, Gurnick 2016). In contrast, the sample of the outer surface also contains meta-smectite, which along with the absence of raw clay indicates that this part of the cube was exposed at higher firing tem pe ra - tures (>600°C) and more precisely between 600°C and 900°C (Shoval 2016; Stevenson, Gurnick 2016; Tarhan, Iºık 2020). Pot 3 (App. 4: 11), Griže clay This pottery sample was made of Griže clay that was tempered with calcite and fired within the expe ri men - tal kiln. The FTIR analyses recorded a principal Si-O stretching curve that splits into two peaks. The first Ceramic cube (App. 2: 5, 6) A pottery cube was made from Renèe clay, without tem - pering, and fired in the experimental kiln. The core and outer surface of this cube were sampled and ana- lysed by FTIR. The spectra recorded a principal Si-O stretching band at 1032cm–1, which is assigned to me - ta-smectite. They also present a combined Si-O/Al-O bending mode (at 469cm–1 for the core and 472cm–1 for the outer surface, respectively) that re lates to the meta-clay component and subsequently supports that this cube mostly consisted of meta-smec tite. Mean- while, the neighbouring shoulder peaks (at 1090cm–1 and 1085cm–1 respectively) are attributed to the over - lap between quartz and a meta-kaolinite component. Nevertheless, the pottery cube retains parts of the raw clay that was not affected by the firing. The FTIR ana- lyses recorded a broad band at 3620cm–1, a shoulder band at 913cm–1 and a band at 532cm–1 (core) and 525cm–1 (outer sur face) that are characteristic of raw smectite. These bands, in particular, are associated with kaolinite–montmorillonite (Chukanov 2014), which is a mineral also detected in the original clay ma- terial (i.e. Renèe clay source). Furthermore, Kaolinite- montmorillonite complies with the recognized meta- clays (i.e. meta-smectite and meta-kaolinite) since they are the ex pect ed outcome after firing this type of mi- neral. Water related to clay components is detected by the very broad H2O-stretching band at 3421cm–1 and the H2O bending mode at 1637cm–1 (outer surface). The presence of quartz is confirmed by the characteristic band-doublet at 779 and 797cm–1, and the minor peak at 694cm–1. Additionally, the spectra included minor bands at 1870 and 1618cm–1, and a shoulder band at 1166cm–1 (1164cm–1 for the outer surface) that are re - lated to SiO2 mineral polymorphs. The presence of the meta-smectite suggests that this ce- ramic material was exposed to temperatures around 600°C and above (Heller-Kallai, Rozenson 1980). The examined sample, though, retains a raw clay com po - nent (i.e. kaolinite–montmorillonite) suggesting that the firing did not consistently maintain high tem pera- tures (>600°C). Meanwhile, the presence of meta-kao- linite does not support temperatures below 450°C, so this pottery cube was probably fired at temperatures between 450 and 650°C. Ceramic cube 2 (App. 3: 7, 8) Another pottery cube was made from Renèe clay, with- out tempering, but fired in an electric kiln. Similar to 422 Manca Vinazza, Petros Chatzimpaloglou Regarding the firing conditions, the meta-clay sup ports fire temperatures between 600°C and 900°C. How- ever, the occurrence of primary calcite does not jus ti- fy temperatures much higher than 700°C. The refore, this pottery sample was most probably fired at tem pe- ratures between 600 and 700°C. Pithos (App. 6–7: 18, 19), Tabor near Vrabèe Samples from the core and outer surface of a pithos (from the Tabor near Vrabèe site) were collected and analysed by FTIR. The core’s spectrum recorded a principal Si-O stretching band at 1032cm–1 which is indicative of a meta-smectite. The combined Si-O/Al-O bending mode at 473cm–1 is also attributed to the meta-clay. However, the band at 534cm–1 is cha rac- teristic of kaolinite–montmorillonite and shows that the sample retains a small part of the original raw clay. Water, associated with the clay components (i.e. raw and meta), is de tected by the H2O-stretching band at 3448cm–1 and the H2O bending mode at 1637cm–1. Meanwhile, the main CO3 band at 1429cm–1, the se- condary band at 875cm–1, and the minor bands at 2512, 1797 and 712cm–1, are indicative of calcite. Bas- ed on the value of the main CO3 band, this is further described as primary calcite (Shoval 2016). Moreover, quartz is iden tified by the characteristic band-doublet at 779 and 799cm–1. The outer surface’s spectrum recorded a principal Si-O stretching band at 1028cm–1 which is associated with raw smectite. Moreover, the band at 534cm–1 is attri- but ed to kaolinite–montmorillonite (Chukanov 2014) and further supports the dominance of raw clay in this sample. The Si-O/Al-O bending mode at 473cm–1, how- ever, is related to a meta-clay component, which in this case is a meta-smectite. Water, related to the clay com- ponents (i.e. raw and meta), is detected by the H2O- stretching band at 3422cm–1 and the H2O bend ing mode at 1637cm–1. Equally with the core, the outer surface also contains an important quantity of calcite. This is recorded with a main CO3 band at 1425cm–1, a secondary band at 875cm–1, and minor bands at 2512, 1794 and 712cm–1. Based on the value of the main CO3 band this is also described as primary calcite (Sho val 2016). Moreover, quartz is identified by the charac te- ris tic band-doublet at 779 and 797cm–1. Regarding the firing conditions, the presence of meta- smectite and primary calcite supports temperatures between 600 to 800°C. However, the detected raw clay (i.e. kaolinite–montmorillonite) indicates that the firing also included temperatures below 600°C. It at 1082cm–1 is assigned to the overlap between the quartz and the meta-kaolinite. Meanwhile, the second at 1046cm–1 falls within the range of 1030–1060cm–1 relating to a meta-smectite composition. The domi- nance of the meta-clay in the sample is supported by the combined Si-O/Al-O bending mode at 473cm–1. Absorbed water is detected by the very broad H2O- stretching band at 3421cm–1. Quartz is identified by the characteristic band-doublet at 777 and 797cm–1, and the minor peak at 694cm–1. The spectrum also in - cluded two minor bands at 1872 and 1618cm–1 and a shoulder band at 1164cm–1 that are related to SiO2 m i neral polymorphs. Lastly, the small CO3 band at 1420cm–1 is associated with primary calcite (Shoval 2016). The reported meta-clays in the sample support firing temperatures between 600°C and 900°C (Shoval 2016; Stevenson, Gurnick 2016; Tarhan, Iºık 2020). How- ever, the occurrence of primary calcite does not justify temperatures much higher than 700°C. Therefore, this pottery sample was fired at temperatures between 600 and 700°C. Pot 4 (App. 4: 10), Veliki Dul clay This pottery sample was made of Veliki Dul clay, which was tempered with calcite and fired within the ex pe - rimental kiln. The collected spectrum recorded a principal Si-O stretching curve that splits into two peaks. The first peak at 1039cm–1 is related to meta- smectite, while the second peak at 1086cm–1 is again associated with the overlap between the quartz and the meta-kaolinite. The dominance of the meta-clay component is further supported by the combined Si-O/ Al-O bending mode at 473cm–1. Absorbed water re lat - ed to the meta-clay is detected by the broad H2O- stretching band at 3420cm–1. Quartz is identified by the characteristic band-doublet at 777 and 797cm–1, and the minor peak at 694cm–1. The spectrum also recorded minor bands at 1870 and 1617cm–1 and a shoulder band at 1166cm–1 that are related to SiO2 mineral polymorphs. Meanwhile, the main CO3 band at 1421cm–1 and the bands at 1793, 878 and 713cm–1 are assigned to calcite, and based on the value of the main CO3 band it is described as pri - mary calcite (Shoval 2016). Lastly, the spectrum in - cluded a band at 3480cm–1 that it has not been pos si- ble to relate to any suitable mineral/component. 423 Investigating the pottery firing techniques in western Slovenia during the Late Bronze and Early Iron Ages ... fired at high temperatures (>600°C), which resulted in the complete transformation of the original clay. Meanwhile, the main CO3 band is associated with pri - mary calcite (Shoval 2016), suggesting firing tem pe - ratures below 800°C. The ceramic situla was thus ex- posed to firing temperatures between 600 and 700°C. Pot (App. 7: 20, 21) Samples from the core and outer surface of a pottery fragment were collected and analysed by FTIR. The spectra recorded a principal Si-O stretching band at 1028cm–1 which is associated with raw smectite. More - over, the band at 534cm–1 (at 535cm–1 for the outer sur - face) is attributed to kaolinite–montmoril lo nite (Chu- kanov 2014) and further supports the do minance of raw clay in this pottery fragment. The Si-O/Al-O bend- ing mode at 474cm–1, however, is related to a meta-clay component which in this case is a meta-smectite. Wa- ter, related to the clay components (i.e. raw and me ta), is detected by the H2O-stretching band at 3422 cm–1 (at 3423cm–1 for the outer surface) and the H2O bend - ing mode at 1637cm–1. Quartz is iden ti fied by the characteristic band-doublet at 778 and 798cm–1 (at 779 and 798cm–1 for the outer surface). Ad ditio nal ly, the spectrum re corded the important presence of cal cite with a main CO3 band at 1425cm–1, a second ary band at 875cm–1, and minor bands at 2512, 1794 and 712cm–1. Having raw smectite as the principal component ge- nerally indicates low firing temperatures (<600°C). However, the presence of a small meta-smectite par- ticle suggests that for a short period the fire reached temperatures of 600°C and above. The main CO3 band falls within the range of 1420–1430cm–1 and is asso ci - ated with primary calcite (Shoval 2016), suggesting firing temperatures below 800°C. The refore, this pot - tery fragment was most likely exposed to firing tem pe - ratures around 600°C. Ceramic petro thin-section The initial focus in the ceramic petro thin-sections in - volved the analysis of Renèe clay, revealing two di- stinct different fabric types. Sample 2 (Fig. 3.1), de riv- ed from a kiln base, exhibits a fabric consistent with firing structures observed in archaeological sour ces (e.g., Quinn 2022.Figs.3.53, 7.12). The presence of nu- merous irregularly oriented planar voids due to the burning out of organic matter – in this case straw – is a characteristic feature. The preparation of the clay was less precise compared to that seen with the vessels, re - sulting in poorly sorted and individually closed in clu - sions. Inclusions, comprising quartz, muscovite mica, seems that the core of the pithos was fired for a long- er period and at high temperatures than the outer surface. We discuss about this in the discussion part and it is not neccesary an error. Silos (App. 3: 9), Štanjel This sample was taken from a large silo that was made from a large clay band. The spectrum recorded a prin cipal Si-O stretching band at 1032cm–1 which is indicative of a meta-smectite. The combined Si-O/Al-O bending mode at 476cm–1 is also related to the meta- clay and confirms that this is the main component of this sample. Absorbed water is detected by the very broad H2O-stretching band at 3431cm–1 and the H2O bending mode at 1636cm–1. Quartz is identified by the characteristic band-doublet at 778 and 797cm–1, and the minor peak at 694cm–1. The spectrum also in- cluded a shoulder band at 1165cm–1 that is related to SiO2 mineral polymorphs. Moreover, the spectrum also reported a main CO3 band at 1420cm–1, a secondary band at 874cm–1, and a minor band at 712cm–1, which are characteristic of calcite. The main CO3 band is assigned to primary calcite (Sho - val 2016), suggesting firing temperatures below 800°C. Meanwhile, the presence of meta-smectite and the absence of raw clay indicate that this pottery was consistently fired at 600°C and above. Hence this silo was exposed to firing temperatures between 600 and 700°C. Ceramic situla (App. 5: 13) The spectrum of this sample recorded a principal Si-O stretching band at 1036cm–1 which is indicative of a meta-smectite. Moreover, there is a shoulder peak at 1085cm–1 that is assigned to the overlap between quartz and meta-kaolinite. The combined Si-O/Al-O bending mode at 474cm–1 is also related to the meta-clay and con- firms that it is an important component of this sample. The spectrum reported the significant presence of cal cite, which was identified by a main CO3 band at 1420cm–1, a secondary band at 875cm–1, and minor bands at 2513, 1794 and 712cm–1. Furthermore, ab sorb - ed water is detected by the H2O-stretching band at 3421cm–1 and the H2O bending mode at 1637cm–1. Quartz is identified by the characteristic band-doublet at 779 and 798cm–1. The spectrum also included a band at 1618cm–1 that is related to SiO2 mineral po ly - morphs. The presence of meta-smectite and the absence of a raw clay component suggest that this ceramic find was 424 Manca Vinazza, Petros Chatzimpaloglou nerals, flint, zircon, and feldspar (indicative of ig ne ous rocks) were also present. Arranged individually, these contribute to a coarse fabric which constitutes 40% of the overall composition. Similarly, the frag ment of the local pot (Sample 20) encompasses 55% inclusions, with calcite dominating at 90%. Apart from a minimal presence of grog grains (0,1%), calcite pre vails as the temper. Other identified inclusions include mono cry - stalline quartz, muscovite mica, and iron-rich clay pel- lets. The homogeneous clay matrix represents 40% of the sample, accompanied by 5% of micro-sized vughs voids irregularly orientated within the clay matrix. The ceramic situla (Sample 13) was tempered with calcite speleothem grains, originating from stalagmite/ stalactite formations, along with grog and clay lumps. The clay lumps exhibit visible cracks, potentially link - ed to the incorporation of fine clay material that un- derwent drying before being mixed with the clay. Other inclusions encompass mono- and polycrystalline quartz, limestone, flint, iron-rich clay pellets, iron- opa que minerals, and muscovite mica. Notably, mu- scovite mica is more prevalent in the grog than in the clay matrix. Planar macroscopic voids are evident, associated with the drying process and the forming of the vessel, particularly those that are parallel in ori- entation. The petrographic results within the Renèe group align with the referencing model for various ceramic forms, including vessels and structures. A comparative ana - lysis between the pottery from Tabor near Vrabèe (Sam- ple 18) and the local clay (Sample 11) validates its local pro ve nance. Moreover, the pottery was tempered with cal cite, grog, and organic matter, consistent with the pre valent practices during the Late Bronze and the be- ginning of the Early Iron Age. The Štanjel group yields even more interesting results. While Pot 5 is identified through a comparison with experimental material sourced from local Veliki Dul clay, the same cannot be asserted for the silo, which incorporates components of igneous rock not native to the Karst. Conversely, the ce ramic situla exhibits a composition entirely derived from local material. Discussion Petrographic analysis has elucidated the utilization of both local and non-local clay sources in archaeological ceramics. Given the geological diversity of Slovenia, which influences the composition of clay sources, we employed a singular clay source, such as Renèe clay, clay pellets, calcite, and ferruginous minerals, occur na turally in the clay and constitute 40% of the com po- sition. Organic matter was used as a temper. Sample 1 (pot 1, tempered with calcite; Fig. 3.2) has the same clay matrix as Sample 2 but lacks organic matter and cal cite temper. Similarly, there are no differences in the clay matrix among the remaining two samples made from the Renèe clay (Samples 5 and 7) (Tab. 1). The subsequent group pertains to the Tabor near Vrab- èe site and consists of two samples: one experimentally made from Griže clay (Sample 11; Fig. 3.3), tempered with calcite, and another from a pithos fragment (Sam - ple 18; Fig. 3.4). The inclusions recorded in these sam- ples, encompassing mono- and polycrystalline quartz, iron opaque minerals, muscovite mica, and iron-rich clay pellets, constitute 30% of the sample. The majority of these inclusions appear as equant rounded or elon- gate rounded particles, with quartz reported as equant subangular. They exhibit a single-spaced and randomly aligned distribution, occasionally forming locally ori - ented planes, resulting in a coarse fabric. Mean while, in the pithos (Samples 18, 19) we identified the pre- sence of calcite and grog temper. The calcite grains ex - hibit intentional cracking, showing equant angular to equant subangular shapes. Additionally, rare grog was detected, a characteristic feature of this period (see Vinazza 2021.433). Other inclusions include mono- and polycrystalline quartz, muscovite mica, iron-rich clay pellets, and iron-opaque minerals. The clay ma- trix reveals evidence of intentional clay mixing, con- tributing to its moderate heterogeneity. Approxi ma tely 10% of the sample is occupied by mac ro and micro- sized voids, characterized as planar and channel-shap- ed. These voids are attributed partly to firing cracks and partly to the remnants of burned or ganic mat ter, uti lized as temper, albeit in minimal quanti-ties. The third group pertains to the Štanjel site and con sti- tutes the most diverse group, involving the analysis of local clay from Veliki Dul (Sample 10; Fig. 3.5), a pre - sumably local pottery type known as a silo (Sam ple 9; Fig. 3.6), a local pot (Sample 20; Fig. 3.7), and a pre su- mably imported ceramic situla (Sample 13; Fig. 3.8). The Veliki Dul clay has 40% inclusions, among which cal cite, mono- and polycrystalline quartz, muscovite mica, iron-rich clay pellets and opaque iron minerals were identified. The silo, pre sumably tempered with calcite, grog, and partially burned organic matter, fea - tures macro- and mega-sized channel-shaped voids (Fig. 3). Quartz is the predominant inclusion, but mu- scovite mica, iron-rich clay lumps, iron-rich opaque mi- 425 Investigating the pottery firing techniques in western Slovenia during the Late Bronze and Early Iron Ages ... Fig. 3. Ceramic thin-section. Photos taken under plain polarized light. 426 Manca Vinazza, Petros Chatzimpaloglou than those at the bottom base. AMS measurements (Vinazza, Dolenec 2022.Fig. 3) agree with the FTIR results, and the lower temperatures at the base pro - bably relate to the fact that the sampled area was un - der the vessels and eventually not in direct contact with the fire. The occurrence of the different temperatures at the different parts of a kiln was con firmed by ther mo - vision camera measurements in another archaeo lo gi - cal experiment conducted in 2018 (Vinazza 2021.Fig. 150). The temperature measured with thermo cou ples in the experimental kiln was 670°C, closely cor res- ponding to the samples taken from the base of the kiln i.e. between 450 and 650°C. Furthermore, the XRD results help refine and narrow down lower tem pera - ture estimates, confirming firing above 550°C (Vi naz - za, Dolenec 2022.396). Combining the FTIR and XRD results yields a final estimated firing temperature rang- ing from 550 to 650°C. This suggests that the FTIR re - sults reflect the firing process very well and help us better understand its complexity. Additionally, the complexity of these results emphasizes the importance of thoughtful consideration before sampling archaeo- logical ma terial. The FTIR results for a pot (Sample 1) initially indicated a broad temperature range between 450 and 900°C, but subsequent XRD results, as reported by Vinazza and Dolenec (2002.396), refined the temperature es- timate to between 550 and 900°C. The FTIR results of the firing pot in pit firing (Sample 12) displayed temperatures around 700°C, aligning closely with the firing temperatures measured by a thermocouple. Despite the short heating time, the FTIR accurately reflected the process. The FTIR results for the pottery samples modelled from local clay Veliki Dul (Sample 10) and Griže (Sample 11) indicated that both pottery vessels were composed of meta-clay, quartz, and calcite, suggesting firing temperatures between 600 and 700°C. These findings fit well with tem pera- tures measured by thermocouples during the firing procedure (i.e. 670°C). In order to distinguish firing structures based on soak - ing time, the FTIR analyses are also very helpful. FTIR results for the first cube indicate exposure to tempe ra - tures ranging from 450 to 650°C. The core retained some raw clay, suggesting lower temperatures (450 and 600°C), consistent with the understanding that the core requires more time to fire. Conversely, the outer surface showed no presence of the raw clay, in - dicating prolonged exposure to higher temperatures throughout the entire operational sequence – from pot shaping to pot firing. Additionally, for processes oc- curring in different firing structures we utilized other clay sources from the vicinity of the aforementioned archaeological sites (Fig 1). The samples from all four clay sources predominantly exhibit a smectitic clay composition. Moreover, those from the Renèe and Veliki Dul clay sources indicated the presence of kaolinite-montmorillonite, a clay mi ne ral polymorph that combines kaolinitic and smec titic com - positions. Quartz is consistently recorded as the se cond most abundant mineral in all the examined sour ces. However, the FTIR results did not detect bands as sign- ed to calcite in any of the clay sources. The FTIR analyses of experimental clay revealed that the kiln dominantly consists of meta-clay and exhibits a higher quartz content. Meta-clay is characterized by a combination of kaolinitic and smectitic origins, re- flecting the clay minerals present in the original clay source. Unexpectedly, findings from the wall (Sample 4) indicate the presence of a small calcite component. Calcite was not reported in the original clay, and pos- sib ly these related to small pebbles that were in the outcrop that was sampled. The FTIR results additionally indicate that the base of the kiln was exposed to lower firing temperatures com - pared to the wall and chimney. The presence of raw clay in the base’s sample suggests temperatures rang- ing between 450 and 650°C, while neither the wall nor chimney retain any traces of raw material. The compo- si tion of the chimney supports a wide range of high temperatures (i.e. 600 and 900°C), while the presence of reformed calcite in the wall’s sample is indicative of temperatures between 700 and 800°C. The suggested temperatures align with those re cord ed by two thermocouples during the conducted expe ri- ment. They indicated that the temperature near the wall exceeded 600°C for at least 30 minutes, while at the base it was maintained for at least two hours. The temperature at the base gradually increased, rea ching around 600°C by the end of the firing pro cedure. Mean while, the temperature rise along the wall did not exhibit a similar pattern, possibly due to the incom plete loading of the kiln and the vessels not being in direct contact with the kiln wall. The sample from the wall of the kiln was taken 10cm above second thermocouple, implying that the selected sample area was in direct contact with the fire, resulting in temperatures higher 427 Investigating the pottery firing techniques in western Slovenia during the Late Bronze and Early Iron Ages ... The next archaeological find from the Štanjel site is a ceramic situla (Sample 13), which was initially pre sum - ed to be an imported ware, but petrological charac te- ris tics revealed that it was tempered with speleothem cal cite, a material commonly found in the Karst caves surrounding the archaeological site. The investigation of the situla also identified the use of grog and clay lumps for tempering. Notably, the grog exhibited a sig- nificantly higher muscovite content compared to the clay matrix, indicating a distinct clay composition. The presence of a planar voids suggests a lack of proper clay preparation. This, coupled with the speleotherm cal cite grains, strongly supports the local production of this situla. Since petrographic analysis revealed no visible de gra- dation of the calcite and the FTIR results support these findings and indicate firing temperatures between 600 and 700°C, this suggest that the situla was indeed fired under controlled environment, such as the one with in a kiln. Moreover, the macroscopic examination reveal- ed ORO firing. All these results strongly support the idea of the existence of a double-chamber kiln in the area under study during the Early Iron Age. Pottery findings from Štanjel contribute also to a hy- pothesis supporting the local production of pottery using at least a one-chamber pottery kiln. To test this hypothesis a pot (Samples 20, 21) from the Štanjel site was examined. The FTIR results indicate temperatures around 600°C, consistent in both the core and outer surface, suggesting that the firing conditions were sta- ble, devoid of temperature fluctuations, a characte ris - tic achievable in a kiln. Furthermore, pe trographic ana - lysis revealed that the vessel was tempered with cal - cite, and no grain decomposition was observed, in di - cative of temperatures below 650°C. The ability to con- trol the firing temperature in a kiln likely facilitated the use of calcite temper, a practice common in this re - gion and elsewhere. Conclusion Archaeological investigations have unveiled the uti li- zation of distinct firing structures by the Late Bronze and Early Iron Age communities in the Karst Plateau. A detailed examination of a variety of firing processes was conducted through the development of an in ter- pretative model based on experimental firings. By synthesizing results from different analyses, it be- comes feasible to understand and accurately interpret (>600°C). For the second cube, the FTIR results clear - ly demonstrated an overall exposure to higher tem pe - ratures (>600°C). The dominance of meta-clay and quartz, coupled with the complete absence of raw clay, suggested temperatures between 600 and 900°C, alig- ning with the temperatures achieved in the electric kiln (i.e. 800°C). Since these results confirmed the laboratory firing tem peratures we can also use this method for the ar- chaeological material. The final step of our investigation involved the appli - cation of FTIR and petrographic analyses to archaeo lo- gical materials, aiming to interpret the firing process that was employed. Starting with the Tabor near Vrabèe site, both the out er surface (Sample 18) and core (Sample 19) of the pi thos were analysed. The FTIR analyses of the outer sur face re vealed a predominance of raw smectite, signifying low firing temperatures. Nevertheless, a small meta- smec tite component was identified, indicating that for a brief period high temperatures were reached (be- tween 600 to 800°C). In contrast, the core exhibited an in creased meta-clay component, indicating consistent exposure to higher temperatures (>600°C). These odd temperature findings between the outer surface and the core may be connected to the vessel’s position during firing, where heat is radiated from the interior to the vessel’s exterior or temperature drop during fi- ring, characteristics more indicative of a bonfire/pit fire rather than of a kiln. Thin-section analysis revealed that this silo (Sample 9) was tempered with calcite, organic matter, and grog. Moreover, the clay matrix included minerals typical of igneous rocks, which are not naturally occurring in the Karst plateau. Notably, it also contains a higher concentration of muscovite mica compared to the lo cal Veliki Dul clay (Sample 10), suggesting a distinct clay origin not indigenous to the area. The FTIR results reindicated that it primarily consists of meta-smectite, quartz and primary calcite. 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Appendix 7