Naima. Gutknecht (HE-Arc CR, Neuchâtel, Neuchâtel, Switzerland) & Rémy. Léopold (HE-Arc CR, Neuchâtel, Neuchâtel, Switzerland) & Domon Beuret. Emmanuelle (Laténium, Neuchâtel, Neuchâtel, Switzerland)
Pin with green-blue and brown shiny corrosion products (Figs. 1-5) and recently developed white corrosion products (see complementary information below). Dimensions: L = 10.5cm; WT = 6.6g.
Hauterive - Champréveyres, Neuchâtel, Neuchâtel, Switzerland
Excavation 1983-1985, object from layer 1
Late Bronze Age
Laténium, Neuchâtel, Neuchâtel
Laténium, Neuchâtel, Neuchâtel
The object has been kept in wooden storage, no intervention documented.
This object was documented in the article "Bronze objects from Lake sites: from patina to bibliography. In: Ancient and historic metals, conservation and scientific research p.41" (Schweizer 1994). The white corrosion layers were not present in this documentation and was noted in 2020. Documentation of the strata in binocular mode of the object was performed in 2022.
The schematic representation below gives an overview of the corrosion structure encountered on the pin from a first visual macroscopic observation.
|Strata||Type of stratum||Principal characteristics|
|CP1||Corrosion product||Dark green, thin, scattered, non compact, very soft|
|CP2||Corrosion product||Dark brown, thin, scattered, compact, hard|
|CP3||Corrosion product||Extra light grey, medium thickness, scattered, non compact, very soft|
|CP4||Corrosion product||Yellow, medium thickness, discontinuous, compact, hard|
|CP5||Corrosion product||Dark grey, medium thickness, discontinuous, non compact, very soft|
|CP6||Corrosion product||Dark green, thin, scattered, non compact, very soft|
|CP7||Corrosion product||Brown, thin, scattered, non compact, very soft|
|M1||Metal||Yellow, thick, metallic, soft|
Table 1: Description of the principal characteristics of the strata as observed under binocular and described according to Bertholon's method.
A fragment (scale) of the white corrosion products close to the head of the pin was taken was sampled. It was turned to powder to be analysed by XRD
XRF with handheld portable X-ray fluorescence spectrometer (NITON XL5). General Metal mode, acquisition time 60s (filters: Li20/Lo20/M20).
XRD (to be completed).
The XRF analysis of the pin was carried out on three representative areas of the surface (Fig. 6). Point 1 corresponds to the bright yellow surface and appears to be an area where the corrosion layers have dissociated to reveal the metal, point 2 corresponds to the dark brown surface (CP2), and point 3 to the white corrosion product (CP3).
The metal is presumably a tin bronze alloy with traces of As. The others elements detected are: S, Si, Fe, Zn, Al.
Results of point 2 indicate an enrichment in Fe and a depletion in Cu and in S in CP2.
Results of point 3 (CP3) are very different to those of points 1 and 2, they indicate the enrichment in Fe and in S and the depletion in Cu and in Sn.
|%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||%||+/- 2σ||Total|
Table 2: Chemical composition of the surface of the pin at three representative areas shown in Fig. 8, Method of analysis: XRF.
lake patina (Schweizer 1994)
In the article "Bronze objects from Lake sites: from patina to bibliography. In: Ancient and historic metals, conservation and scientific research" (Schweizer 1994), the corrosion products of the pin 18603 (LAB MAH 86-77) are identified as copper iron sulfide (chalcopyrite) and as copper sulfate (antlerite). The first one is brown-yellow (probably CP2) and the other one is green (probably CP1).
The corrosion structure has only been documented in binocular mode (Fig. 9).
The pin is made from a tin bronze. The corrosion products of the pin 18603 (LAB MAH 86-77) originally formed were identified as copper iron sulfide (chalcopyrite) typical of lake patina and copper sulfate (antlerite).
The white corrosion (CP3) seems to have developed after excavation (to be completed).
References on object and sample
Object files in MiCorr
1. MiCorr_Pin or needle fragment HR-3031
2. MiCorr_Tang fragment of a knife HR-6567
3. MiCorr_Tang fragment of a knife HR-6246
4. MiCorr_Pin HR-18152
5. MiCorr_Pin HR-3071
6. MiCorr_PIN HR-17773
7. MiCorr_Pin HR-3389
8. Rychner-Faraggi A-M. (1993) Hauterive – Champréveyres 9. Métal et parure au Bronze final. Archéologie neuchâteloise, 17 (Neuchâtel), pl. 67/22.
9. Hochuli, S. et al. (1988) SPM III Bronzezeit , Verlag Schweizerische Gesellschaft für Ur- und Frühgschichte Basel, 76-77, 379.
10. Empa Report 137 695/1991, P.O. Boll.
11. Rapport d'examen, Lab. Musées d'Art et d'Histoire, Geneva GE, 87-194 à 87-197.
12. Schweizer, F. (1994) Bronze objects from Lake sites: from patina to bibliography. In: Ancient and historic metals, conservation and scientific research (eds. Scott, D.A., Podany, J. and Considine B.B.), The Getty Conservation Institute, 33-50.
References on analytic methods and interpretation
13. Robbiola, L., Blengino, J-M., Fiaud, C. (1998) Morphology and mechanisms of formation of natural patinas on archaeological Cu-Sn alloys, Corrosion Science, 40, 12, 2083-2111.