Investigation report Period

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1 Holvenstraat, 9 B-3900 Overpelt, Belgium Tel/fax : hebolabo@hotmail.com btw : BE HRH: Investigation report Overpelt, 19 august 2017 Commissioned by Mr. Sebastien Janssens Bosdreef 25 B-8020 Oostkamp Belgium Concerning: Authenticity of an archaic Chinese lidded bronze Tripod Ding Fig.1 Period : China, Zhou dynasty, Spring and Autumn Period ( BC) 1/

2 Description: Round tripod (cabriole legs) bronze Chinese Ding (cooking vessel) with flat lid (cover) and two angular square-shaped, upright handles. The lid is centered on top with a fixed ring surrounded with three decorated J-stands. The belly is round bottom shaped. Vessel and lid are single band decorated. All decorations are dragon design curled patterns. Total surface (outside and inside) corrosion: green, blue and reddish. The ding has been used for cooking (coal rests on the outside bottom of the vessel). Frequent soil residues at the surface (traces of excavation) Fig.2 2/ Fig. 3

3 Measurements: Handle Lid ring Lid Lid stand Belly Belly ring Leg Total height (table to lid) 241 mm Diameter belly without handles 310 mm Total diameter belly with handles 390 mm Belly ring height to lid (top) 62 mm width 4 mm Diameter lid min /max 310/328 mm Height lid without stands 22 mm Lid stand height 54 mm thickness 4 mm Lid ring diameter 55 mm Handles height 120 mm width 94 mm thickness mm Wall thickness 5-8 mm Weight 11,80 kg Origin The ding was a food vessel used for cooking, and genuine examples often show signs of burning on the undersides. The standard ding had three legs and many examples had two lug handles. Later (especially late Zhou) dings sometimes had lids. 3/

4 Fig. 4.a,b,c Shape references: lidded dings of Chinese Zhou dynasty Spring & Autumn period The bronze tripod ding was one of the most important ritual vessels in ancient China (Zhou dynasty c BC). Bronze at this period was a very valuable metal. The importance of a Chinese family was reflected in the size and grandeur of their bronze vessels. While the Shang bronzes seem mainly to have been used for ritual purposes and frequently buried with the dead, by the Eastern Zhou, numbers of bronze vessels were being made for daily use. Other were not made for burial but for paying respects to the ancestors. The huge amount of genuine bronze dings are excavated artefacts. That s why there is always a natural corrosion on the surface witch can be distinguished from contemporary falsifications. The Chinese ancient bronze formula consist of hugely varying percentages of copper, tin and lead, occasionally with (maybe unintentional) traces of other elements(zinc, iron and silver). Bronze was not worked by smithying but casting in sectional clay molds. The fine northern clays of China enabled very fine imprints of designs to be transferred to the bronze, which was poured into the gaps between the clay moulds (separated by small bronze spacers). So in the majority of bronze objects molding lines and traces of spacers should be present (sometimes only visible by radiography). 4/

5 Observation of molding characteristics. Fig. 5a 5.b 5.c The mould lines are marked on legs and belly ( Fig. 5 a,b,c) 5/

6 Used pouring method for archaic Chinese bronzes until Han Dynasty (pouring in clay molds) Example of casting a ding. The cross section of the mold assembly (a) shows how the pieces fit together. Spacers are used to make sure that the casting space does not shift or close during pouring. The spacers in the bottom of the vessel need to be larger, to counteract the upward hydrostatic pressure on the inner core when the metal is poured in. The bronze is poured in through one leg (b). The other legs serve as air vents. (info Getty Inst: Chinese Bronzes: Casting, Finishing, Patination, and Corrosion by W. T. Chase) Fig.6 Detail of Fig. 5.c (outside of the belly) Due to corrosion the pouring lines on the belly are rather difficult to see. 6/

7 Fig. 7 The rectangular handles are conically moulded and poured together with the ding. Fig. 8 The ring in the center of the lid has been poured together with the lid (not forged or welded) Fig. 9 Barn traces at the bottom of the ding 7/

8 Figs.10 pouring and air venting gaps into the bottom of the legs. Fig.11 Inlay spacers (mold lines) on the bottom of the vessel to moderate upward hydrostatic pressure on the inner core when the metal was poured in. (see marks) Fig. 11b,c references of bottom inlay spacers on Chinese ding Spring & Autumn period (Zhou dynasty) 8/

9 Fig.12 Unsolved spacer at the outside of the bottom Conclusion: All observations indicate a manufacture during the Zhou dynasty. No deviations were observed. Observations concerning the use of the ding. The underside of the ding is grey to black coloured (see Fig.13) due to deposits of carbon. These deposits partially obstruct the corrosion of the bronze. Also are still carbon remains against the cast edge of the bottom plate. (see Fig.14) Fig.13 Black grey underside of the ding with deposits of carbon partially preventing corrosion 9/

10 Fig. 14 Deposits of carbon at the inner side of the cast edge (underside of the ding) Conclusion: It is likely that the ding has been used for cooking and was not intended for burial purposes. Observations of the corrosion layers. Several corrosion layers are observed outside as well inside the ding. There are white, red, green and blue corrosion layers on the surface of the bronze. The minor white and major red layers are directly in contact with the metal surface as they were formed at the first. By use of a metallographic microscope one can see that the corrosion is incrusted into the metal surface. Further the green layers are formed later out of the red layers. At least the blue corrosion crystals are formed on top of the green corrosion layer. Determination of the white layer (see Fig.15) by Hydr- ICP ( Hydrid generation Inductive Coupled Plasma Spectrometry) after dissolution with tartaric acid / nitric acid. Results: Tin (Sn) ± 60% Lead (Pb) 3% Zinc (Zn) 0.2% The white layer is tin oxid. Fig.15 White corrosion layer (SnO 2 tin oxid) in contact with the metal surface. 10/

11 Determination of the red layer (Fig.17) by Raman spectroscopy. Fig.16 Comparison of the reference Raman spectrum of cuprite Cu 2O (lower plot) with the spectrum of the red corrosion layer shown in Fig.17 (upper plot). (traces of lead white) Fig. 17 Red corrosion layer ( Cu 2 O copper oxid - cuprite) in contact with the metal surface. 11/

12 Determination of the green layer (Fig.19) by Raman spectroscopy. Fig.18 Comparison of the reference Raman spectrum of malachite Cu 2 (CO 3 )(OH) 2 (lower plot) with the spectrum of the green corrosion layer shown in Fig.19 (upper plot). Fig. 19 Green corrosion layer (Cu 2 (CO 3 )(OH) 2 malachite) 12/

13 Determination of the blue layer (Fig.21) by ATR-FTIR (Fourier Transform Infrared Spectrometry). Fig.20 Comparison of the reference FTIR spectrum of azurite Cu 3 (CO 3 ) 2 (OH) 2 (lower plot) with the spectrum of the blue corrosion layer shown in Fig.21 (upper plot) Fig.21 blue upper corrosion layer Cu 3 (CO 3 ) 2 (OH) 2 azurite 13/

14 Observation of the corroded metal surface by inversed metallographic microscopy Malachite (green) Tin oxid (white) Cuprite (red) Bronze core Magnification x 240 Fig.22 The corrosion crystals are grown into the metal core. This is a natural process that can t be artificially obtained. Control on the presence of nitrates by spectrophotometric analysis of the corrosion layers. (sulpho fenolate method). Result: No nitrates were detected. (<0.005%) Conclusion: The corrosion layers are all natural formed. Building up the layers (Fig.23), as well as the ingrowth in the metal surface, answering to the natural corrosion process of archaic bronze. Also the absence of nitrates indicate that the corrosion is not contemporary artificially applied. Buildup of the corrosion layers: Cuprite (red) in contact with the metal surface Malachite (green) formed from the cuprite corrosion layer Azurite (blue) formed from the malachite corrosion layer Fig.23 Buildup of the corrosion layers at the bronze surface Composition of the bronze metal A sample of the metal was obtained by milling the cast edge on the outer sides of the bottom plate.(see Fig.24) Sample dissolution by tartaric acid / nitric acid. Element analysis done by ICP.(Agilent E720) 14/

15 Fig.24 Place of sampling on the outside at the cast edge of the bottom Results: Element value unit Ag 0,084 % As 0,42 % Bi 0,04 % Co 0,032 % Cr 0,006 % Cu 67,3 % Fe 0,39* % Mg 0,34* % K 0,057* % Sr 0,011* % Sb 0.26 % Si 0,12* % Pb 21.9 % S 0,36 % Zn 0,21 % P 0,30 % Ni 0,041 % Sn 9,0 % <0,005% = Cd, Ge, In, Mn, Tl, V, Mo, Be, Ga, Li, U, Au, Hf, Pt, Ru, Nb, Re, Ta, Ti, W, Zr, Ir, Al * :may be contaminated by soil at surface level Conclusion: High lead (Pb) concentrations in bronze are typical of archaic Chinese bronzes. Mn, Ni, As, Si, Zn and Cd should not exceed 1% Statement None of the observations or analyses give rise to a suspicion of forgery or contemporary copy. On the contrary they are in full compliance with references of archaic bronze objects from the late Zhou dynasty (spring and autumn period BC). This Chinese bronze ding, as examined here and described to the best of our ability, can be declared as authentic. This statement is an opinion and therefore gives no right to redress or liability of any kind. Overpelt, 2017 august 19th RJM. Bové 15/