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Figure 37 – uploaded by Georgia S . Kordatzaki

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Fig 17a. Test sherd from the Cretan clay fired at 700° C/3 min in a FHR controlled firing. Photo by Nikos Gerakakis — Figure 17 a. Test sherd from the Cretan clay fired at 700° C/3 min in a FHR controlled firing. Photo by Nikos Gerakakis

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Georgia Kordatzaki, Independent researcher, Greece gkordat@gmail.com (mailto:gkordat@gmail.com) This study assesses the impact of firing on burnished ceramic surfaces. For this task, two main factors related to burnishing were examined and evaluated, the reflection of the ceramics and pottery surface sheen. Macroscopic observations on the burnished surface were made with the naked eye. A series of experiments was conducted to explore the ways in which traditional firing conditions affect pottery surfaces. Data was gathered from four different firings, including three open-air dung firings and one wood-firing in an updraft kiln. Additional testing was carried out under controlled conditions in the laboratory. The aim was to further investigate and determine the specific thermal characteristics that influenced the burnished pottery and use the feedback to approach burnishing disturbance in traditional conditions. The data showed that certain thermal profiles and characteristics cause a reduction in burnishing on ceramic surfaces, with the rise in temperature, among others, being a significant one. The type of clay also proved to be an important factor regarding the way in which the reduction in burnishing progresses. The present inquiry constitutes the first part of an ongoing research project that will be completed with

Table 1. Firing structure in association with fuel type and dung arrangement. Four traditional experimental firings were carried out to investigate the impact of past conditions on burnished pottery. Specifically, two major types of structure were used (See Table 1), including a depression, where three open-air firings took place, and a two-chamber, wood-firing updraft kiln, for the fourth firing (for more on firing structures, see Gosselain, 1992, p.246 fig.1; Gosselain and Livingstone Smith, 1995, p.153 fig.4; Livingstone Smith, 2001). The open-air dung firings were conducted at Hallstatt in the context of the 1st pottery workshop organised in 2022 by H. Reschreiter of the Naturhistorisches Museum in Vienna. The kiln firing took place at Asparn an der Zaya at the MAMUZ Museum in 2020. The open-air dung firings were executed by L. and V. Albustin, S. Gutter, H. Reschreiter, and M. Zavadil together with the author. The kiln firing was carried out by F. Ugrinovits. n order to effectively reduce additional parameters that may hinder the comparison of the different open- air firings, the subsequent process was followed:

siven the above, full documentation of every single traditional firing was carried out (See Table 2) with the nain focus on the following thermal characteristics: maximum temperature, heating rate (average 2=mperature per minute to reach the maximum temperature), soaking time (namely, time the pottery was ubjected to above specific temperature thresholds, for example, above 700° C, 800° C or 900° C, and/or it its maximum).

Table 2. Detailed thermal characteristics of the traditional firings (max temp.: maximum temperature) Controlled experimental firings

Moreover, the test of 900° C, VSHR/3 min was not conducted. Table 3. Main thermal characteristics of the controlled firings in the laboratory in correlation to the reflection and sheen of the test sherds (FHR: fas heating rate; VSHR: very slow heating rate). Twenty-four heavily burnished test sherds of the same thickness were prepared. All sherds were pinched and finally beaten on a mould. They were then fired under controlled, oxidising conditions in a Nabertherm L-151K2TNL 15/12/C450 muffle furnace (for the controlled testing, the equipment of the Fitch laboratory, British School at Athens was used). Four main series of controlled firings were performed (for example, fo! he 1000° C, see Graph 1) with the following thermal characteristics (See Table 3): 1. Fast heating rate FHR) and 3 minutes soaking time (at maximum temperature; see Graph 2); 2. FHR, 1 hour soaking time at maximum temperature); 3. FHR, 3 hours soaking time (at maximum temperature); 4. Very slow heating rate (VSHR), 3 minutes soaking time (at maximum temperature). Four different maximum emperatures/temperature thresholds were consistently regulated (700° C, 800° C, 900° C, and 1000° C) in each of the main series of firings. The exception to the above were the test sherds that were kept for hree hours at the maximum temperature and, due to general funding limitations, fired only at 1000° C. Moreover, the test of 900° C, VSHR/3 min was not conducted.

Table 4. Detailed thermal characteristics of the controlled firing conditions in the laboratory (max temp.: maximum temperature; FHR: fast heating rate; VSHR: very slow heating rate).

Fig 1. A heavily burnished, still unfired pot, manufactured by the author, that shows specular reflection and very bright sheen. Photo by Nikos Gerakakis

Fig 2. The interior of the updraft wood-firing kiln with the lateral open sides. Photo by Georgia Kordatzaki

Fig 3a. Depiction of the sheen in different parts of a burnished pot (vb: very bright, v: velvety, s: soft, d: dull, dr: dull and rough). Photo by Georgia Kordatzaki

Fig 3b. The arrow illustrates the position of the burnished pot at the interior of the updraft wood-firing kiln. Photo by Georgia Kordatzaki

Fig 4a. The very bright side of a pot. Photo by Nikos Gerakakis Fig 4b. The dull side of the pot depicted in Fig 4a. Photo by Nikos Gerakakis

Fig 5a. Stem of an experimental pot burnished with leather. Photo by Georgia Kordatzaki

Fig 5b. Stem of an experimental pot burnished with wood. Photo by Georgia Kordatzaki

Fig 5c. Stem of an experimental pot burnished with pebble. Photo by Georgia Kordatzaki

Fig 6a. Linear burnishing marks on the surface of the unfired test sherd from the Euboean clay. Photo by Nikos Gerakaki:

Fig 6b. Linear burnishing marks on the surface of the unfired test sherd from the Cretan clay. Photo by Nikos Gerakakis

Fig 7a. Characteristic burnishing striations, as observed under a digital handheld microscope: field of view 1.3 cm. Photo by Georgia Kordatzaki

Fig 7b. Characteristic burnishing striations, as observed under a digital handheld microscope: field of view 1.1 cm. Photo by Georgia Kordatzaki

https://exarc.net/issue-2024-3/ea/approaching-pottery-burnishing-through-experimental-firings

Fig 8b. First open-air firing: a layer of sod covered the structure. Photo by Georgia Kordatzaki Fig 8a. First open-air firing: dung arrangement and pottery load. Photo by Georgia Kordatzaki

Fig 9. For the second open-air firing, an admixture of goat dung and some straw was used as fuel. Photo by Georgia Kordatzaki

Fig 10. Four multiple layers of an admixture of goat dung and some straw covered the pottery of the third open-air firing and used as the main fuel type. Photo by Georgia Kordatzaki

Fig 11. The wood-firing updraft kiln used for the fourth firing. At the central lower part, a dull and rough goblet from the Cretan clay i visible. Photo by Georgia Kordatzaki

Fig 12a. First open-air dung firing: very bright pot from the Euboean clay. Photo by Nikos Gerakakis

Fig 12b. First open-air dung firing: very bright pot from the Cretan clay. Photo by Nikos Gerakakis

Fig 13a. Second open-air dung firing: the sheen of the Euboean pot looks velvety. Photo by Nikos Gerakakis

Fig 13b. Second open-air dung firing: the underside of the Euboean pot. Photo by Nikos Gerakakis

Fig 13c. Second open-air dung firing: the sheen of the Cretan vase appears bright. Photo by Nikos Gerakakis

Fig 13d. Second open-air dung firing: the underside of the Cretan vase. Photo by Nikos Gerakaki:

Fig 14a. Third open-air dung firing: the sheen of the Euboean pot appears soft. Photo by Nikos Gerakakis

Fig 14b. Third open-air dung firing: the underside of the Euboean pot. Photo by Nikos Gerakakis

Fig 14c. Third open-air dung firing: the sheen of the Cretan vase appears soft. Photo by Nikos Gerakakis

Fig 14d. Third open-air dung firing: the underside of the Cretan vase. Photo by Nikos Gerakakis

Fig 15a. Pot from the Euboean clay that was fired in the updraft, wood-firing kiln (fourth firing). Photo by Nikos Gerakakis

Fig 15b. Pot from the Cretan clay that was fired in the updraft, wood-firing kiln (fourth firing). The pot showed advanced lime spalling Photo by Nikos Gerakakis

Fig 16a. Test sherd from the Euboean clay fired at 700° C/3 min in a FHR controlled firing. Photo by Nikos Gerakakis

Fig 16b. Test sherd from the Euboean clay fired at 800° C/3 min in a FHR controlled firing. Photo by Nikos Gerakakis

Fig 16c. Test sherd from the Euboean clay fired at 900° C/3 min in a FHR controlled firing. Photo by Nikos Gerakakis

Fig 16d. Test sherd from the Euboean clay fired at 1000° C/3 min in a FHR controlled firing. Photo by Nikos Gerakaki:

Fig 17b. Test sherd from the Cretan clay fired at 800° C/3 min in a FHR controlled firing. Photo by Nikos Gerakakis

Fig 17c. Test sherd from the Cretan clay fired at 900° C/3 min in a FHR controlled firing. The sherd showed advanced lime spalling. Photo by Nikos Gerakakis

Fig 17d. Test sherd from the Cretan clay fired at 1000° C/3 min in a FHR controlled firing. The sherd showed advanced lime spalling Photo by Nikos Gerakakis

Fig 18a. Test sherd from the Euboean clay fired at 700° C/1 hin a FHR controlled firing. Photo by Nikos Gerakakis

Fig 18b. Test sherd from the Euboean clay fired at 800° C/1 hin a FHR controlled firing. Photo by Nikos Gerakakis

Fig 18c. Test sherd from the Euboean clay fired at 900° C/1 h in a FHR controlled firing. Photo by Nikos Gerakakis

Fig 18d. Test sherd from the Euboean clay fired at 1000° C/1 h in a FHR controlled firing. Photo by Nikos Gerakakis

Fig 19a. Test sherd from the Cretan clay fired at 700° C/1 h in a FHR controlled firing. Photo by Nikos Gerakakis

Fig 19b. Test sherd from the Cretan clay fired at 800° C/1 h in a FHR controlled firing. Photo by Nikos Gerakakis

Fig 19c. Test sherd from the Cretan clay fired at 900° C/1 h in a FHR controlled firing. The sherd showed advanced lime spalling. Photo by Nikos Gerakakis

Fig 19d. Test sherd from the Cretan clay fired at 1000° C/1 h in a FHR controlled firing. The sherd showed advanced lime spalling. Photo by Nikos Gerakakis

Fig 20a. Test sherd from the Euboean clay fired at 700° C/3 min in a VSHR controlled firing. Photo by Nikos Gerakaki

Fig 20b. Test sherd from the Euboean clay fired at 800° C/3 min in a VSHR controlled firing. Photo by Nikos Gerakakis

Fig 20c. Test sherd from the Euboean clay fired at 1000° C/3 min in a VSHR controlled firing. Photo by Nikos Gerakakis

Fig 21a. Test sherd from the Cretan clay fired at 700° C/3 min in a VSHR controlled firing. Photo by Nikos Gerakakis

Fig 21b. Test sherd from the Cretan clay fired at 800° C/3 min in a VSHR controlled firing. Photo by Nikos Gerakakis

Fig 21c. Test sherd from the Cretan clay fired at 1000° C/3 min in a VSHR controlled firing. The sherd showed early lime spalling. Photo by Nikos Gerakakis

Fig 22a. Test sherd from the Euboean clay fired at 1000° C/3 hrs in a FHR controlled firing. Photo by Nikos Gerakaki:

Fig 22b. Test sherd from the Euboean clay fired at 1000° C/3 min in a VSHR controlled firing. Photo by Nikos Gerakaki:

Graph 1. Heating curves of the four main series of controlled firings at 1000° C in the laboratory (FHR: fast heating rate, VSHR: very slow heating rate). Graph by Georgia Kordatzaki

Graph 2. Heating curves of the FHR/3 min firings at four different controlled temperatures in the laboratory (FHR: fast heating rate). Graph by Georgia Kordatzaki

Graph 3. Comparison of the heating curves of the third open-air dung firing and the fourth updraft kiln firing. Graph by Georgia Kordatzaki

Related topics:

Experimental Archaeology Prehistoric Archaeology Pottery (Archaeology)Neolithic Archaeology Neolithic & Chalcolithic Archaeology Neolithic Europe Pottery technology and function Pottery kilns

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