Effect of firing temperature and atmosphere on ceramics made of NW Peloponnese clay sediments. Part I: Reaction paths, crystalline phases, microstructure and colour

doi:10.1016/j.jeurceramsoc.2010.02.002

Journal of the European Ceramic Society

Volume 30, Issue 9, July 2010, Pages 1841-1851

https://doi.org/10.1016/j.jeurceramsoc.2010.02.002 Get rights and content

Abstract

Archaeometric investigation on ancient ceramic collected from excavations in NW Peloponnese demonstrated that the ancient potters used the local Plio-Pleistocene clay sedimentary deposits for a large historical period. Three representative raw materials of these local sediments were chosen for experimental work aiming to evaluate their firing behaviour in a propane-fired kiln, with a different atmosphere and temperature. The determination of mineralogy and microstructure was carried out by XRD and SEM-EDS analysis. For ceramics fired at 850 and 950 °C, no significant mineralogical and microstructural differences were observed between the oxidising and reducing atmosphere. The main pyrometamorphic phases are fassaite, gehlenite, anorthite and wollastonite. On the contrary, at 1050 °C in reducing atmosphere, gehlenite and wollastonite are diminished whereas the content of anorthite, fassaite and amorphous phase is higher. The higher vitrification is attributed to Fe²⁺ that participates either in the formation of eutectic phases or in low melting crystalline phases.

Introduction

The study of the macroscopic and microscopic characteristics of ancient ceramic sherds may be very helpful enabling a deeper understating of – among others – the provenance, the dating, as well as the ceramic processing followed by the potters of the time. The analysis on non-glazed sherds typically involves a number of complementary techniques, such as colour determination for both the surface and the core, major, minor and trace element analysis, crystalline/amorphous phase analysis, study of the microstructure by optical and electron microscopy (scanning, cathode-luminescence and transmission), Mössbauer spectroscopy and more.

Provided the above analyses have permitted the identification of the clay deposits used and the assessment of the ceramic processing employed, it is expected as a final step to reproduce the ceramic sherd by achieving a material with comparable micro and macro characteristics as that produced by the potters of the time. A number of works are devoted in such a reproduction process and in the study of the pathways of clay firing, however, results mainly derive from ceramics fired in resistance (i.e. muffle/electric) furnaces in oxidising atmosphere.1, 2, 3, 4, 5, 6, 7, 8, 9 Nonetheless, ancient Greek ceramics have been fired under both oxidising and reducing conditions (e.g. 10, 11), and the same applies to non-Greek potteries as well.4, 12 Despite the great interest in this field, a relatively small number of works are devoted to the study of firing in reducing conditions,13, 14, 15, 16, 17 which is counterbalanced by a substantial interest in the technical literature.18, 19

To assess the effect of firing conditions on the mineralogy and microstructure of clay-based ceramics, and therefore provide direct comparison between contemporary and ancient bodies, ceramics were fired in oxidising and reducing atmospheres in a propane-fired kiln. Raw materials were collected from local Plio-Pleistocene sediments, close to Patras, prefecture of Achaia, NW Peloponnese. Excavations in this region give evidence of activity of ceramic manufacturing during Archaic (6th c. B.C.), Hellenistic (3rd c. B.C.) and Roman (1st–3rd c. A.D.) period.²⁰ Previous research on collected fine wares has led to the conclusion that the artefacts have been most probably produced from the clay sediments used in this study. This is supported by a number of findings, such as the mineralogy and particle size distribution and most notably the geochemistry between ceramics and clay sediments.21, 22, 23

The goal of this study is to provide a set of results that would assist during the interpretation of ancient ceramic sherds and find application in the contemporary ceramic industry. An extended micro-chemical analysis on the crystalline phases as well as a comparison between the microstructures produced here with the ancient ceramic sherds is presented in Part II.²⁴

Section snippets

Experimental

The three raw materials used in the experiments, G, TS and TH, have been collected from the region of Patras. Details concerning the sampling location and their geological context are provided elsewhere.21, 23 Analysis on the methods employed for the chemical and mineralogical analysis is also provided in the previously cited work. The organic content has been determined by pyrolysis at 400 °C for 16 h.²⁵ The particle size distribution has been measured by laser scattering (Hydro 2000M, Malvern,

Raw materials

The chemical analysis of the raw materials, Table 1, reveals that Fe₂O₃, MnO, MgO, Na₂O, K₂O, TiO₂ and P₂O₅, range in comparable levels. The main difference regards the levels of SiO₂, 42.03–51.17 wt%, Al₂O₃, 10.48–12.80 wt%, CaO, 9.48–13.97 wt% and the loss on ignition, 14.03–21.76 wt%. The content of organic material was 2.15 wt% for G, 2.10 wt% for TH and 1.88 wt% for TS.

The mineralogical analysis, Table 2, shows that the materials are composed of quartz, albite (NaAlSi₃O₈), orthoclase (KAlSi₃O₈),

Conclusions

The following conclusions are derived:

(a)
The effect of the kiln atmosphere for firing at 850 and 950 °C is not intense as the microstructure and mineralogy of the bodies appears to be similar. The body is characterised by open, interconnected porosity whereas the major neo-crystallised minerals are fassaite, gehlenite, anorthite and wollastonite. Difference in colour is observed when fired at 950 °C.
(b)
Comparison between the bodies fired at 850 and 950 °C, under a specific firing atmosphere, reveals

Acknowledgements

Prof. P. Tsolis-Katagas and Assoc. Prof. G.N. Angelopoulos of University of Patras, are gratefully acknowledged for their support during this work. YP is also thankful to the Research Foundation – Flanders for the post-doctoral fellowship.

References (49)

F. González-García et al.
Firing transformations of mixtures of clays containing illite, kaolinite and calcium carbonate used by ornamental tile industries
Appl Clay Sci
(1990)
Y. Maniatis et al.
Technological examination of Neolithic-Bronze Age pottery from central and southeast Europe and from the Near East
J Archaeol Sci
(1981)
L. Nodari et al.
Hematite nucleation and growth in the firing of carbonate-rich clay for pottery production
J Eur Ceram Soc
(2007)
M.P. Riccardi et al.
An approach to the dynamics of clay firing
Appl Clay Sci
(1999)
M.J. Trindade et al.
Mineralogical transformations of calcareous rich clays with firing: A comparative study between calcite and dolomite rich clays from Algarve, Portugal
Appl Clay Sci
(2009)
B. Moroni et al.
Technological features of Renaissance pottery from Deruta (Umbria, Italy): an experimental study
Appl Clay Sci
(2006)
L. Maritan et al.
Influence of firing conditions on ceramic products: experimental study on clay rich in organic matter
Appl Clay Sci
(2006)
C. Rathossi et al.
Technology and composition of Roman pottery in northwestern Peloponnese, Greece
Appl Clay Sci
(2004)
C. Rathossi et al.
Effect of firing temperature and atmosphere on ceramics made of NW Peloponnese clay sediments: Part II. Chemistry of pyrometamorphic minerals and comparison with ancient ceramics
J. Eur Ceram Soc
(2010)
J. Jauhiainen et al.
Emissions from pyrolysis and combustion of olive oil solid waste
J Anal Appl Pyrolysis
(2005)

Y. Pontikes et al.

Effect of firing temperature and atmosphere on sintering of ceramics made from Bayer process bauxite residue

Ceram Int

(2009)

E.T. Stepkowska et al.

Influence of microstructure on firing colour of clays

Appl Clay Sci

(1992)

P. Duminuco et al.

Firing process of natural clays. Some microtextures and related phase compositions

Thermochim Acta

(1998)

B. Bauluz et al.

TEM study of mineral transformations in fired carbonated clays: relevance to brick making

Clay Miner

(2004)

G. Cultrone et al.

Carbonate and silicate phase reactions during ceramic firing

Eur J Miner

(2001)

T. Peters et al.

Mineralogical changes during firing of calcium-rich brick clays

Am Ceram Soc Bull

(1978)

J.V. Noble

The technique of attic vase-painting

Am J Arch

(1960)

J.M. Pérez et al.

Pigment identification in Greek pottery by Raman microspectroscopy

Archaeometry

(2004)

I. Shimada et al.

Early pottery making in northern coastal Peru. Part IV: Mössbauer study of ceramics from Huaca Sialupe

Hyperfine Interact

(2003)

J.E. Houseman et al.

Influence of kiln atmospheres in firing structural clay products. I. Maturation and technological properties

J Am Ceram Soc

(1971)

J.E. Houseman et al.

Influence of kiln atmospheres in firing structural clay products. II. Color development and burnout

J Am Ceram Soc

(1971)

Y. Maniatis et al.

Effect of reducing atmosphere on minerals and iron oxides developed in fired clays: the role of Ca

J Am Ceram Soc

(1983)

G.P. Souza et al.

Effect of varying quartz particle size and firing atmosphere on densification of Brazilian clay-based stoneware

J Am Ceram Soc

(2006)

J.A.M. Denissen

Reduction firing of building ceramics. Part I

Ziegelindustrie Int/Brick Tile Indus Int

(1993)

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Effect of firing temperature and atmosphere on ceramics made of NW Peloponnese clay sediments. Part I: Reaction paths, crystalline phases, microstructure and colour

Abstract

Introduction

Section snippets

Experimental

Raw materials

Conclusions

Acknowledgements

Appl Clay Sci

J Archaeol Sci

J Eur Ceram Soc

Appl Clay Sci

Appl Clay Sci

Appl Clay Sci

Appl Clay Sci

Appl Clay Sci

J. Eur Ceram Soc

J Anal Appl Pyrolysis

Ceram Int

Appl Clay Sci

Thermochim Acta

TEM study of mineral transformations in fired carbonated clays: relevance to brick making

Clay Miner

Carbonate and silicate phase reactions during ceramic firing

Eur J Miner

Mineralogical changes during firing of calcium-rich brick clays

Am Ceram Soc Bull

The technique of attic vase-painting

Am J Arch

Pigment identification in Greek pottery by Raman microspectroscopy

Archaeometry

Early pottery making in northern coastal Peru. Part IV: Mössbauer study of ceramics from Huaca Sialupe

Hyperfine Interact

Influence of kiln atmospheres in firing structural clay products. I. Maturation and technological properties

J Am Ceram Soc

Influence of kiln atmospheres in firing structural clay products. II. Color development and burnout

J Am Ceram Soc

Effect of reducing atmosphere on minerals and iron oxides developed in fired clays: the role of Ca

J Am Ceram Soc

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J Am Ceram Soc

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