CIRAM Authentication Of Metal Objects - 2013

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A very good document from CIRAM lab. to understand how it is possible to test metal objects.

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CIRAM Authentication Of Metal Objects - 2013

  1. 1. CIRAM Analysis – Works of art Analysis, authentication and dating of works of art CIRAM Analysis Analysis and dating of cultural heritage CIRAM Archaeology Analysis and dating of archaeological artefacts CIRAM Track Safe marking and traceability of objects AUTHENTICATION OF METAL OBJECTS: SCANNING ELECTRON MICROSCOPY AND X-RAY RADIOGRAPHY Why developing a crossed approach? ENSCPB 16, Avenue Pey-Berland – Chem’Innov – 33607 Pessac cedex – France Tel.: +33 5 57 34 21 18 Fax:+33 5 56 23 45 35 www.ciram-art.com Contacts : Drs Olivier Bobin et Emmanuel Vartanian Version UK 1.0 mise à jour le 16 février 2009 CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  2. 2. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 2 / 17 The analysis’s steps X-ray radiography Manufacturing techniques Corrosion areas Restoration areas « Dating » / Antiquity test Thermoluminescence on the residual cores (heated mineral) Preferentially on closed objects (man, animals…) Surface analysis Tool marks : burnishing, polishing... Superficial deposits: burial sediments, corrosion products… Surface treatments : build patina, putting in color of gold, cleaning, acid attack, … Material analysis Composition of the alloy Degree and kind of the corrosion Origin of the corrosion From the necessity of having a crossed approach X-ray Radiography Thermoluminescence, if possible Scanning electron microscopy CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  3. 3. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 3 / 17 The X-ray radiography It allows to evaluate the structural homogeneity of the piece and reveals: the restoration areas the corrosion areas some technological indications The metal is quite corroded. We We observe the traces of the vent observe pieces maintained by holes and of the wax feeder tube metallical quot;plastersquot;. (“tire-cire”), between the forelegs. We observe defects of casting and/or restoration. CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  4. 4. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 4 / 17 The « dating » THE THERMOLUMINESCENCE This technique allows obtaining the approximate dating of the last firing of the object. The analysis is conducted on the heated mineral: the core. This approach is efficient only on casting objects. 8000 7000 Intensité TL (u.a.) 6000 5000 Nat Nat + 3,0 Gy 4000 Nat + 6,0 Gy Bruit de fond 3000 2000 intensité TL entre 250 -400 °C Dose naturelle (Gy) 160000 1000 140000 Intensité TL (u.a.) 0 50 100 150 200 250 120000 300 350 400 450 Température (°C) 100000 80000 ancient 60000 40000 20000 -1,8 Dose (Gy) 0 -3 -2 -1 0 1 2 3 4 5 6 7 Dose Naturelle 8000 Intensité TL (u.a.) 7000 Nat 6000 Nat + 6,0 Gy Nat + 9,0 Gy 5000 Bruit de fond recent 4000 3000 intensité TL entre 350 -400 °C Dose naturelle (Gy) 20000 2000 18000 1000 Intensité TL (u.a.) 16000 0 14000 50 100 150 200 250 300 12000 350 400 450 Température (°C) 10000 8000 6000 4000 2000 Dose (Gy) -0,2 0 -2 0 2 4 6 8 10 Dose Naturelle Limits The core must not have been exposed to the light or polluted and its origin is sometimes uncertain. CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  5. 5. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 5 / 17 Characteristics of a metal THE MATERIAL Generally, it has to do with an alloy. The use of pure metals is relatively rare. Bronze: copper, tin, lead … Brass: copper, zinc, tin, lead… Gold: often alloyed with copper and silver. Silver: often alloyed with copper, lead… S C Heterogeneous material with different phases. ITS DETERIORATION Secondary corrosion Clay deposits products Healthy metal Corrosion products Corrosion at the surface CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  6. 6. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 6 / 17 Characteristics of a metal Why does the metal’s composition constitute the first step of the study? ⇒ Some elements are modernity indicators. ⇒ The corrosion process depend on the nature of the material (silver, gold, …) or of the alloy (bronze, brass, …). The chemical extraction process of aluminium was developed in 1827 by Friedrich Wölher ! But the composition of the metal can not be considered as a fundamental proof of authenticity, the interpretation can depend on the knowledges … Zn : 37% before 2003 The ancient calamine technique does not permit to obtain more than 33% of Zn: modern process developed around 1820 and spread after 1850. after 2003 Article of J.M. Welter in Techné (n°18, p.27-36): Ancient brass with 35 to 40% of Zn Modern making of brass at 40% of Zn with calamine process CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  7. 7. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 7 / 17 The surface analysis The tools’ marks Hammering traces, burnishing, polishing… decor by incisions … Manual incisions Traces of mechanical burnishing Manual burnishing modern work with ⇒ ancient work modern tools or ⇒ recent work with an ancient technic SUPERIFICAL DEPOSITS They contain elements which correspond to the surface treatments used (traditional or modern). Acid attack with the ferric Amorphous material constituted Acid attack with aqua regia: chloride to simulate copper of silver and copper that does smouth surface and corrosion and burial deposits. not correspond to corrosion microporosities. products. ⇒ Modern application on a modern object ⇒ Modern acid attack ⇒ Putting in color of gold to simulate the corrosion (traditional) or ⇒ Modern acid attack CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  8. 8. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 8 / 17 The surface analysis THE CORROSION PRODUCTS They result from the interaction between the material and its environment. They come from long and natural process, or from an acid attack… Green Malachite White lead blue azurite blue ultramarine red cuprite Green of Scheele ⇒ Natural products of a ⇒ Application of pigments, natural or artificial to simulate corrosion the corrosion products SURFACE ANALYSIS, IN SUMMARY: Preliminary study that allows to exclude the obvious fakes: Modern shaping, ferric chloride, acid attacks, pigments… Complementary study to cross-section analysis, to characterize decorations and to observe the whole object. Study necessary, but not sufficient to determine the age of an object. As a complement, analysis by PIXE (Particul Induced X-Ray Emission) external beam (identical to AGLAE, the installation of the Louvres laboratory C2RMF) permits a nondestructive study of the object and gives a quantification of the major elements, of the minor ones and of the traces (hundred of ppm ; 0,01% = 100 ppm). CIRAM exclusivity This technique permits the authentication, since the ancient alloys contain many traces elements (Pb, Pt, Sn, Sb, Fe, As, Bi…), whereas modern metals are almost pure. Principally powerful for gold or silver objects CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  9. 9. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 9 / 17 The corrosion of metals Which are the characteristics of the corrosion according to the metal? What is called quot;patinaquot;? Is the corrosion of the metal natural or artificial? The results form a beam of clues that will permit us to give our opinion on their compatibility or not with the presumed age of the object. Typical conclusions These results indicate that the object has not undergone any corrosion from a natural and long time, subsequent to the manufacturing phase. These results are inconsistent with the presumed period of the object. These results indicate that the object is corroded and indicate the damages correspond to a long and natural weathering subsequent to the manufacturing phase. These results are consistent with the presumed period of the object. CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  10. 10. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 10 / 17 CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  11. 11. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 11 / 17 Copper alloys corrosion THE CHARACTERISTICS OF THE DETERIORATION – The intern dendritic corrosion The intern dendritic corrosion corresponds to the preferential decay of the copper rich phase, in comparison to the tin rich phase which is more resistant. It develops along the dendrite and penetrates the interior of the material. The copper rich phase The copper rich phase is quite corroded is superficially corroded THE CHARACTERISTICS OF THE DETERIORATION –The tin-enrichment The preferential corrosion of the copper rich phase leads to a superficial increasing of tin and to the formation of green to blue tin oxydes. Sn = 35% wt NB : in that case the presence of phosphorus indicates a funeral burial context instead of an attack with phosphoric acid. Sn = 13% wt CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  12. 12. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 12 / 17 Copper alloys corrosion THE CHARACTERISTICS OF THE DETERIORATION – Inter and trans-granular corrosion Inter-granular corrosion corresponds to the preferential deterioration of the grain boundaries and leads to a superficial decohesion. Trans-granular corrosion develops throughout the different phases. Inter-granular corrosion Trans-granular corrosion Inter and trans-granular corrosion THE CHARACTRISTICS OF THE DETERIORATION – The lead globule corrosion The corrosion phenomena involve the draining of lead to the surface. At the same time we observe the corrosion of the lead globules and their gradual replacing by copper oxides. (cuprite). Draining of lead Corrosion of lead globules and gradual replacing by copper to the surface oxides. CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  13. 13. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 13 / 17 Copper alloys deterioration THE CHARACTERISTICS OF THE CORROSION – The quot;patinaquot; The quot;patinaquot; corresponds to the corrosion products made by the alloy deterioration: We detect copper salts: cuprite (red copper oxide), malachite (green carbonate), atacamite (green chlorides), azurite (blue carbonate) and blue to green sulphates. We detect blue to green tin oxides. We also detect silicate deposits associated to corrosion products. azurite malachite and green tin oxides Red cuprite quot;healthy metalquot; quot;Noble patinaquot; THE CHARACTERISTICS OF CORROSION, in summary : The intern dendritic corrosion The superficial tin increasing The inter and trans-granular corrosion The lead globule corrosion The quot;patinaquot; The depth of the corrosion penetration Is it necessary to observe all these criteria, to establish that a metal object is naturally corroded? Is it possible to reproduce artificially this process? CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  14. 14. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 14 / 17 Copper alloys corrosion ARTIFICIAL CORROSION or FAKE PATINA To accelerate or simulate the corrosion, one have to use surface treatment with strong acids (hydrochloric, sulphuric, and phosphoric acid...). It is also possible to bury the object during some months or some years. ⇒ Front of attack is linear and quot;smoothquot;. The corrosion does not penetrate deep into the material. ⇒ Cl, S and P elements attest a chemical attack. We only detect copper chlorides as corrosion products. ⇒ There is no interpenetration between the corrosion products and the superficial deposits. Obvious fake: quot;Intelligentquot; fake: the alloy is corroded, the The alloy is not corrosion products are natural and their corroded colour reminds the quot;noble patinaquot;. Others kinds of alloy corrosion SILVER ALLOYS Corrosion phenomena observed on silver alloys are similar to those of copper alloys: Preferential corrosion of the copper rich phase and intergranular corrosion. Development of superficial microfissures and microporosities, embrittlement. Formation of silver salts. Indications about the manufacturing techniques (hammering, lamination…). Superficial porosity and embrittlement The micromorphology multilayered indicates a lamination phase. GOLD ALLOYS Gold is very resistant to corrosion (it does not oxidize). Only copper and silver phases can be corroded. The authenticity research will principally base on surface studies and on the traces elements (PIXE external beam). CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  15. 15. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 15 / 17 In summary… The authentication research uses a beam of clues that permits to define: The nature of the alloy The degree of the corrosion The origin of the corrosion The surface analysis permits to obtain complementary information: The tools’ marks The superficial deposits The decorations Nevertheless, these techniques of analysis have limits: They are not dating methods. They only study slow processes: efficient for objects aged of at least 300 years old. The samplings are limited compared to the sizes of the object. It would be necessary to define, in complement, the degree of homogeneity and deterioration of the object, with X-ray radiography. Nowadays, new fakes are made and the only microanalysis is not sufficient any more, because it can conclude the object is ancient whereas it is not. The homogeneity degree of the object Case #1 The microanalysis shows that the alloy is naturally and amply corroded. quot;Ancientquot; object Modern montage that associates a recent metal and an ancient one. The ancient metal is located at the level of the base of the object where samplings are generally made. CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  16. 16. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 16 / 17 The object homogeneity degree Case #2 The microanalysis indicates the alloy is not corroded and that the patina is artificial. O O quot;fakequot; object The sample was made on a restoration area. A second sample (at the base of the object) showed results compatible with the presumed age. Case #3 We observe technical elements, The microanalysis indicates the alloy is naturally and deeply fissures and restoration areas. corroded. We observe a noble patina. All this results are compatible with the presumed age of the object. The X-Ray radiography was performed in first step; The sample was made in a chosen area. The scanning electron microscopy analysis confirms the object is ancient. CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com
  17. 17. Version UK 1.0 mise à jour le 16 février 2009 Metals analysis Page 17 / 17 In summary… The authentication research involves the complementarity of the approaches and of the analysis methods: Characterization of the interne structure and of the homogeneity of the object Analysis of the constitutive material of the object Analysis of the degree and the nature of the corrosion CIRAM proposes a wide range of analysis permitting to bring the information necessary to a rigorous search of authentication. CIRAM SARL au capital de 21.000 € ENSCPB – Chem’Innov Tél. & Fax : 00.33.(0)5.56.23.45.35 480 825 652 RCS Bordeaux - APE 7112B 16 avenue Pey Berland Portable : 00.33.(0)6.66.63.80.99 SIRET 480 825 652 00021 33607 Pessac Cedex E-mail : contact@ciram-art.com N° TVA Intracommunautaire FR 56 480 825 652 France Site web : www.ciram-art.com

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