Miniature Agricultural Implements GEM 7381 14,16,29,32,34,35 & 80740-41
Abdelaziz. Elmarazky (The Grand Egyptian Museum, None)
In 1922, the tomb of Tutankhamun (KV62) was accidentally discovered by Howard Carter. It is considered the most prominent tomb in the valley of kings (Luxor Governorate) since it contained valuable objects such as gold jewelry, chariots, thrones, and musical instruments. The miniature agricultural implements (Fig. 1) and the shawabti figures (Fig. 2) were found together inside the resin-coated wooden kiosks (Fig. 3) (Allen 2006). They contained 413 shawabti figures and 1866 miniature agricultural implements, such as hoes, yokes, and baskets (Carter 1933). The main function of these figures and their instruments is to carry out all duties in place of the deceased king in the afterlife (Torres 2014). The shawabti figures are made of wood, alabaster, quartzite, and other materials, whereas the miniature agricultural implements are made of copper or faience. The copper is often covered with a pale blue corrosion product.
Tool
The Tomb of Tutankhamun, Luxor, Luxor, Egypt
1922
Late Bronze Age
The New Kingdom
Indoor atmosphere
The Grand Egyptian Museum, Giza, Egypt
The Grand Egyptian Museum, Giza, Egypt
GEM 7381-14,16,29,32,34,35 & 80740-41
Alfred Lucas’ notes indicated that the implements were chemically cleaned with sulfuric acid and ammonia solutions (Lucas [1927] 2016). Then, they were transported to the Egyptian Museum in Cairo (EMC).
None.
The schematic representation below gives an overview of the corrosion structure encountered on the miniature hoe (GEM 7381/35) from a first visual macroscopic observation.
Stratum | Type of stratum | Prinicipal characteristic |
CP1 | Corrosion product | light green, crust, isolated, matte, thin, opaque, compact, fariable, irregular, fariable, irregular, loosely |
CP2 | Corrosion product | pale blue, crust, discontinuous, matte, thin, opaque, matte, compact, fariable, irregular, and loosely |
CP3 | Corrosion product | dark red, layer, continuous, compact, soft, opaque, tough, matte, bumby, adherent |
M1 | Metal | pink, soft, medium, continuous, compact, brittle, smooth, and adherent |
Table 1: Description of the principal characteristics of the strata according to Bertholon's method.
The pale blue corrosion samples (Figs. 4&5) were gently removed with a toothpick from the miniature hoe (GEM 7381/35).
Cu-based alloy
Cold worked (laminated)
The Grand Egyptian Museum, Giza, Egypt
The Grand Egyptian Museum, Giza, Egypt
Sept.2016. identification of the chemical composition of unusual pale blue corrosion product.
None.
Analysis Performed:
Non-invasive technique
- X-ray Fluorescence (XRF): Handheld Thermo Fisher Scientific Niton XL3t analyser, Mining mode, Aquisition time 60s.
Invasive techniques
- X-ray diffraction (XRD): PANalytical PW3040/60 X’pert PRO diffractometer using Cu Kα radiation and analysing the powder samples at 40 KV.
- Fourier transform infrared spectroscopy (FTIR) IR: Prestige-21 instrument in combination with IR solution software. The KBr pellet technique was used for sample preparation.
- Environmental scanning electron microscopy (SEM): Quanta FEG-250 for high-resolution imaging. The composition analysis was performed using backscattered electron imaging (BSE).
XRF was conducted directly on GEM7381/29, which revealed the presence of copper as a major element and tin as a minor element. Cl (chorides) and probably S (sulfur) are pollutants. The same elements but with higher amounts were found on the other corroded agricultural implements GEM 7381/8 and GEM7381/36 and GEM 7381/8.
Element | 7381/29 | 7381/36 | 7381/8 |
Cu | 81.3 | 70.1 | 73.8 |
Sn | 0.5 | 1.4 | 2.5 |
S | 0.2 | 0.2 | 7.8 |
Cl | 0.2 | 6.3 | 3.7 |
Table 2: Chemical composition of the surface of the corroded miniature implements.
The metal itself has not been microscopically examined, however the elemental composition could be deduced from XRF results as shown in Table.2.
None
Cu
Sn
None.
The pale blue corrosion sample from a hoe (7381/35) was examined (Fig.8) and identified using SEM–EDX (Fig.9), which detected copper and sodium as major elements (Table 3).
Element | Weight (%) | Atomic (%) | Net.Int | Error (%) |
O K | 22.3 | 41.5 | 11.9 | 10.2 |
NaK | 27.0 | 34.4 | 7.8 | 13.9 |
CuK | 50.6 | 23.6 | 13.3 | 6.6 |
Table 3: Chemical composition of pale blue corrosion sample.
With FTIR, OH− stretching bands appear at 3446 and 3568 cm−1(Fig. 10). The band at 1602 cm−1 represents the presence of a carbonyl group C=O. The bands at 1359 and 1375 cm−1 are from the carbonate region (Table 4).
Absorption bands | Wavenumber (cm-1) |
OH stretching bands | 3568 |
CH stretching bands | 2933 |
C=O stretchnig bands | 1602-1409 |
(CO3)-2 stretching bands | 1375-1359 |
Table 4: FTIR spectra of the pale blue corrosion sample.
The XRD patterns of the pale blue corrosion sample (Fig. 11) do not correspond to the copper corrosion product standards in the International Centre for Diffraction Data (ICDD) (Table 5).
d-spacing [Å] | Intensity [%] |
11.06 | 100 |
10.29 | 13.45 |
8.17 | 23.53 |
7.76 | 9.03 |
7.23 | 29.81 |
6.53 | 8.51 |
5.54 | 27.25 |
4.58 | 7.97 |
4.23 | 5.1 |
3.51 | 11.28 |
3.36 | 9.38 |
3.04 | 8.14 |
2.90 | 10.58 |
2.78 | 25.07 |
2.66 | 3.83 |
2.54 | 24.17 |
2.47 | 56.69 |
2.36 | 21.57 |
2.33 | 29.33 |
2.28 | 25.52 |
Table 5 : XRD patterns of the pale blue corrosion product.
Generally, the presence of a sodium element in the corrosion products indicates that the copper objects were either buried in soils rich in sodium chloride (Ghoniem 2016) or cleaned using chemical solutions containing sodium (Paterakis 2003). In the case of the miniature agriculture implements, the objects had been housed in wooden kiosks for thousands of years and had not been in contact with the Egyptian soil.
Similarities were detected in the FTIR spectra of the sodium copper carbonate acetate found on ancient Egyptian bronzes (Thickett and Odlyha 2000) and on the Athenian Agora collections (Paterakis 2003) (Table. 6). The presence of the carbonyl group acetate CH3COO− can be attributed to emissions of organic carboxylic acids from wooden cupboards in storage areas (Paterakis 2010), or to previous conservation treatment residues (Paterakis 2003). For instance, in the case of incomplete removal of disodium ethylene diamine tetraacetic acid (2Na-EDTA) solution, residues of acetic acid can react with the metal surface of the treated object (Paterakis 2010). In 1955, a pale blue corrosion product on ancient Egyptian collections was identified as chalconatronite [Na2Cu(CO3)2.3H2O] (Grettens and Frondel 1955). Acetate-containing corrosion products resulting from the absorption of acetic acid gas from wooden cupboards may be altered products of chalconatronite (Wang et al. 2009).
The presence of an OH− stretching band at 3000 and higher indicates water or a basic OH− mineral (Paterakis 2003). Carbonate might have originated from the carbonate corrosion product (Thickett and Odlyha 2000), carbon dioxide in a storage area (Paterakis2003) or previous conservation treatments such as sodium sesquicarbonate (Wang et al. 2009).
Absorption bands | Copper acetate (Derrick.etal, 2000) | The mininature hoe of Tutankhamun in GEM | Ancient Egyptian Collection in BM (Type A) | Ancient Athenian Agora collection |
OH stretching bands | 3200-3550 | 3568 | 3416 | 3394 |
CH stretching bands | 2933 | 2817 | 2858 | |
CH3COO- stretching bands |
1550-1650 1400- 1450 |
1602-1409 | 1588-1413 | 1600-1538 |
(CO3)-2 stretching bands | 1359-1375 | 1347 | 1348 |
Table 6: Comparison of the pale blue corrosion samples, a sample of miniature agricultural implements resembles"copper acetate standard" and the FTIR spectra of sodium copper carbonate acetate (Thickett and Odlyha 2000, Paterakis 2003).
Sodium copper carbonate acetate [NaCu(CO3) (CH3COO)] was found on ancient Egyptian bronzes in the British Museum (BM) (Thickett and Odlyha 2000) and on the Athenian Agora collection (Paterakis 2003) (Table. 7). The XRD result of the pale blue corrosion found on the miniature agricultural implements resembles the intensities and d-spacings published in the studies above.
The mininature hoe of Tutankhamun in GEM | Ancient Egyptian Collection in BM (Type A) | Ancient Egyptian Collection in BM (Type B) | Ancient Athenian Agora Collection | ||||
d-spacing [Å] | Intensity [%] | d-spacing [Å] | Intensity [%] | d-spacing [Å] | Intensity [%] | d-spacing [Å | Intensity [% |
11.06 | 100 | 10.5 | 100 | 11 | 50 | ||
10.29 | 13.45 | 10 | 40 | ||||
8.17 | 23.53 | 8 | 70 | 8 | 30 | 8.6 | 40 |
7.76 | 9.03 | 7.5 | 50 | ||||
7.23 | 29.81 | 7.2 | 60 | ||||
6.53 | 8.51 | 6.5 | 50 | 6.7 | 100 | 6.7 | 100 |
5.54 | 27.25 | 5.5 | 20 | ||||
4.58 | 7.97 | 4.7 | 10 | 4.7 | 50 | ||
4.23 | 5.1 | 4.3 | 30 | ||||
3.51 | 11.28 | 3.52 | 10 | 3.8 | 30 | ||
3.36 | 9.38 | 3.31 | 10 | 3.35 | 40 | 3.25 | 80 |
3.04 | 8.14 | 3.03 | 30 | 3.03 | 20 | 3.15 | 80 |
2.9 | 10.58 | 2.92 | 10 | ||||
2.78 | 25.07 | 2.75 | 10 | 2.78 | 30 | 2.78 | 60 |
2.66 | 3.83 | 2.67 | 10 | 2.65 | 30 | 2.63 | 80 |
2.54 | 24.17 | 2.55 | 30 | 2.58 | 10 | ||
2.47 | 56.69 | 2.44 | 10 | 2.45 | 30 | 2.45 | 60 |
2.36 | 21.57 | 2.38 | 10 | 2.37 | 30 | 2.37 | 70 |
2.33 | 29.33 | 2.32 | 10 | 2.3 | 10 | 2.3 | 50 |
2.28 | 25.52 | 2.08 | 10 |
Table 7: XRD spectra of pale blue corrosion found on miniatre hoes from Tutankhamun, Ancient Egyptian collection in BM and Athenian Agora collection.
Unknown
Unknown
None.
Multi-technique analysis of corrosion products can provide valuable information about the condition of the objects, particularly if there are no records of conservation-restoration intervention and storage. In the case of miniature agricultural implements, treatment was carried out on site by Alfred Lucas, and they were then transported to the Egyptian Museum in Cairo (EMC). Since then, there has been no information on the condition and subsequent treatments. The pale blue corrosion product has been identified as sodium copper carbonate acetate. It is attributable to both chemical cleaning and VOC emissions from the storage wooden cabinet. Indeed, it is assumed that the miniature agricultural implements were chemically cleaned with a sodium-containing solution and then stored in the EMC's wooden cabinet. The chemical cleaning of archeological metal objects is a controversial practice in museums and its harmful effects must therefore be taken into account. If it is necessary to use chemical cleaning on metal objects, they should be rinsed with distilled water and dried with ethanol to remove the residues of the chemical cleaning. Wooden cabinets should be avoided to ensure the integrity of metal objects and protect them from potential damage.
References on historical background:
1. Allen,S. (2006) Tutankhamun's Tomb: The Thrill of Discovery [Book], The Metropolitan Museum of Art.
2. Carter, H. (1933) The Tomb of Tutankhamun: Treasury&Annex, [Book], Casserole and Company.
3. Torres, Ines. (2014) Funerary stratigraphy in Tutnkhamun's tomb, [Book], The Oxford University.
4. Lucas, A. (1927) Notes on conservation of objects from the tomb of Tutankhamun, [Online], The Griffith Institute Series, The University of Oxford. [Accessed]- 10-Feb-2016. http://www.griffith.ox.ac.uk/discoveringTut/conservation/4lucasn5.html.
References on analytical methods and interpretation:
1. Derrick,M and etal. (2000) Infrared spectroscopy in conservation science [Book], Getty Conservation Institute.
2. Ghoniem,M. (2016) Characterization and scientific conservation of a group of archaeological bronze Egyptian statues [Journal], International Jornal of Conservation Science, Vol. 7, pp. 95-108.
3. Paterakis,A.B. (2010) The formation of acetate corrosion on bronze antiquities: characterization and conservatiion, [PhD], University College London.
4. Paterakis,A.B. (2003) The influence of conservation treatmentand the environmental storage factors on corrosion of copper alloys in ancient Athenian Agora [Journal], Journal of the American Institue for conservation, Vol.42, pp. 313-339.
5. Paterakis, a.B. (2016) Volatile organic compounds and the conservation of inorganic materials [Book]. Archetype Publications.
6. Getten, R.J. and Frondel,C. (1955) Chalconatronite: An alteration product on some ancient Egyptian bronzes [Journal] Studies in Conservation, Vol.2, pp.64-75.
7. Thickett, D. and Odlyha,M. (200) Note on the identification of an unusual pale blue corrosion product from Egyptian copper alloy artefacts [Journal], Studies in Conservation.Vol 45, pp.63-67.
8. Wang, Q. and etal (2009) Bronzes from the scared animal necropolis at Saqqara, Egypt; a study of the metals and corrosion [Journal], studies in conservation, Vol. 45, pp.73-82.