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Analysis of Ancient Faience

Two analytical techniques were employed to exam ancient faience artifacts from the Petrie Museum:

Optical analysis
Using a magnifying glass and optical microscope proved to be very useful to study the surfaces and the exposed area resulted from chipping or breaks. This examination helped in identifying the materials and the technological features (see What).

SEM analysis
The objects were examined by the scanning electron microscope (SEM) in the Wolfson Archaeological Science Laboratories at the Institute of Archaeology. This examination helps to characterise the different areas in the artefact i.e surface, glaze, interaction zone and core paste. Also the elemental analysis reveals information on the composition and the raw materials.

Scanning electron microscope (SEM) in Wolfson Archaeological Science Laboratory, UCL Institute of Archaeology

For this study we used, a Hitachi S-3400N SEM attached with an Oxford instrument of energy dispersive spectroscopy EDS. The samples and objects were examined at working distance of 10mm without a conductive carbon-coating using a low voltage of 3-10kV to minimize charging. We used secondary electron imaging (SE) to distinguish various particles in the core paste, interaction zone or in the glaze layer. Also we used backscattered electron imaging (BSE) to help in identifying differences in particles compositions. Then EDS was used to generate elemental composition of certain areas of the samples to understand the chemical structure of the samples and the distribution of elements across the different zones. However this data is generally qualitative due to the irregular surfaces of the examined samples.
Samples preparation and analysis:

The samples examined for this project included:

Faience frog amulet UC1176
Analysis of surface at three areas to identify the colouring oxides:

Scanning electron microscopy image of frog’s head showing analyzed area from eye    Scanning electron microscopy image of frog’s head showing analyzed area of body

Scanning electron microscopy image of frog’s leg showing analyzed area

Spectrum processing
Processing option: Oxygen by stoichiometry (Normalised)

 
COMPOUNDS %
FORMULA
Head
Eye
Leg
Na2O

2.56

1.86

3.69

MgO

0.89

 

1.14

Al2O3

3.71

1.99

3.33

SiO2

65.67

74.09

73.60

SO3

3.68

 

5.76

K2O

1.69

0.67

1.07

CaO

4.34

0.68

3.14

FeO

2.38

3.18

1.28

CuO

6.25

7.25

4.77

PbO

6.07

8.25

 

Discussion
The analysis shows that:

  • Copper oxide is the colourant used to obtain the blue glaze on the amulet
  • Lead oxide and higher amounts of copper oxide and iron oxide were used for the eyes to give the green-colour glaze

Faience paste in ancient moulds
2mm samples were removed from the moulds and examined in the SEM:

Scanning electron microscopy image of faience paste sample from mould of ring showing crushed quartz grains
Sample from a mould found at Amarna for ring shank UC24141

 

Scanning electron microscopy image of faience paste sample from mould of petal showing  analyzed area and crushed quartz grains
Sample from a mould found at Amarna for a flower petal UC24109

 

Scanning electron microscopy image of faience paste sample from mould of Bes figure showing analyzed area and crushed quartz grains
Sample from a mould of Bes found at Amarna UC47126

Spectrum processing
Processing option: Oxygen by stoichiometry (Normalised)

 
COMPOUNDS %
ELEMENTS
FORMULA
Ring
Petal
Bes

C

CO2

16.46

15.13

18.50

Na

Na2O

0.19

 

0.05

Mg

MgO

 

0.46

0.21

Al

Al2O3

 

0.39

0.77

Si

SiO2

81.26

77.89

74.18

Ca

CaO

1.61

0.94

1.82

Fe

FeO

 

0.77

1.49

Cu

CuO

0.48

3.87

2.37

O

       

This page last modified 6 November, 2009 by Kathryn E. Piquette


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