2.6. PIXE Analysis of Metals, Paper and other Artifacts

Transcription

1 2.6. PIXE Analysis of Metals, Paper and other Artifacts

2 The surface of Karomama Karomama, daughter of the Theban Priest Nimlot of the southern empire. She married Takelat II of the north cementing the union of the southern and northern Egyptian empire. Among the Egyptian antiquities was a statuette of Queen Karomama, of the twenty-second dynasty. It was thickly covered with green rust. The conservators suspected it was no ordinary example of bronze and it was resolved to carefully remove the coating. As the operation went on the character of the metal changed. Finally it was discovered that the bronze was damascened with gold and silver, and that much ornamentation was spent over the royal robes. (Arthur Lee 1890) (report on original analysis of surface corrosion.)

3 The microstructure of surface layers Two faces of Egyptian egida ca 500 BC, (Louvre, Paris) Depth profiling of surface with high energy proton PIXE techniques to obtain, composition, structure and corrosion properties identification of original surface below material and corrosion build-up. Sacred Amon worshipper Karomama, ca 820 BC - 22nd dynasty, (Louvre, Paris) Bronze statuette, inlaid with gold, silver, black a white paste (eyes)

4 Surface Deterioration of Bronze PIXE scan: 50x150μm % chlorine concentration 15μm into corrosion layer 0.12 % chlorine concentration >50μm depth Cu Pb Ni Sn Corrosion Copper chlorid

5 Metal Soldering Main tube of diadem Au Au Au Au Ag Au Fe Cu Zr Ag Myrtle wreath, gold, Greek/Macedonian; 4th century BC Analysis of soldering technique for conservation & reconstruction Gold leaf of diadem Au Au Gold-copper alloy Au Au Zr Au Cu Zr Ag Ag

6 The Achaemenid Pendant The Achaemenid هخامنشيان empire was founded by Cyrus the Great in 559 BC 4th century BC Excavated from Iranian tomb motif represents deity with two birds flying in front. 28 old balls soldered to tubes bent from thin old sheets and soldered together. G. Dermortier, Bucl. Instr. Method. B 14 (1986)

7 PIXE view of the Achemenide pendant Relief work with fairly constant Au and A content; Fe shows at joints and solder points, tube shows high Cu concentration

8 A B C PIXE analysis of solder joints D gold A B C D A B silver C D copper Solder connections clearly recognizable; composition of each solder alloy reveals ancient soldering technique: Brazing with Cu-Ag-Cu alloy at point A,B happened at T 800 o C with slow cooling. At C joint by local fusion of elements at T 1000 o C, reduction of less noble elements at D copper diffusion bonding at T 900 o C, Cu diffuses into Au at T<Au melting point providing very hard bond.

9 Cadmium and Forgery The Vespasian necklace, Cadmium in ancient metalwork indicates forgery! supposedly from the 1st century AD. The three center medallions show images of Vespasian, Titus, Domitian.

10 Detailed Analysis of medallion Systematic micro-beam analysis Reveals Cd enrichment at solder points G. Dermortier & T. Hackens, Nucl. Instr. Meth. 197 (1982)

11 Experimental Arrangement Mapping out silvercopper solder material

12 Micro-beam analysis of Cu-Ag-Au solder However, Cd can be in ore material. Modern solders show anticorrelation between Cadmium and Copper. This solder shows correlation between Cd and Cu which indicates ancient origin!

13 Authenticy check for ship wreck coins

14 Nuestra Senora de Atocha

15 Treasures from the Atocha

16 Doubts about the authenticy of some of the Atocha Escudos on the market

17 Analysis of Spanish Escudos 18th century escudo fake metal content of Spanish Escudo 18th century escudo content [%] Au Ag metal Fe escudo 1 escudo 2 escudo 3 escudo 4 suspect coin Cu suspect coin escudo 4 escudo 3 escudo 2 escudo 1 coins metal content of Spanish Escudo Suspect coin has considerably higher Au content and less Ag content than Spanish Escudo content [%] 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% escudo 1 escudo 2 escudo 3 escudo 4 suspect coin coin Cu Fe Ag Au

18 Nature of ink and pigments with PIXE PIXE has developed into a major analytical tool (like X-ray fluorescence) to investigate ink and pigments in old manuscripts and parchments. The main goal is to understand ancient production processes and the associated chemical techniques. Further goals are: to identify authors and artists of ancient paintings to detect and identify forgeries. gallic acid + FeSO 4.7H 2 O + water iron-gall ink

19 Nature of ink and pigments with PIXE Ritualistic talmudic texts had to be written with special ink. During the 12th and 13th century a bitter dispute between talmudic scholars about the question which kind of ink does really fulfill the ritualistic requirements: indian ink used by French Jews gall ink used by German Jews A decision was made not to accept iron- but only copper vitriol since the last 6th century entry into the Talmud (summary of ancient Rabbi decisions) mentioned gall-apples & copper vitriol. PIXE analysis of parchment shows strong iron content, in disobedience of the decision!

20 Trionfo d Amore Botticelli Drawing The drawing is attributed to Botticelli the author of the incipit is unknown! Petrach manuscript, Biblioteca Classense Ravenna, Fiesole Pigment analysis with PIXE to determine the technique and origin of paint.

21 PIXE analysis of Trionfo d amore Book holder construction to focus beam onto the series of pre-selected points in the drawing.

22 Paint analysis The results showed that ochres with addition of a lead base pigment, were used to obtain the brown colour. Iron-gall ink was used to trace the drawing. Lead point was used in the preparation of the drawing. It was not possible to identify the Lilac pigment used. The blue colour of the sky is a lead based pigment deposited on top of an underlying mixture of blue pigments.

23 Ink and paper of the Gutenberg bible Deep black ink after 500 years Analysis of many single letters showed that ink had unusually high copper (Cu), nickel (Ni), and lead (Pb) concentration high printing quality!

24 Letter identification through PIXE Use of the lateral resolution of a microprobe permits the study of small details in the material. For example PIXE analysis of paper content combined with statistical methods leads to the identification of faint letters. photograph Greek handwriting of letter χ on papyrus PIXE image G. Löwestamm & E. Swietlicki, Nucl. Instr. Meth. B43 (1989) 104

25 Comparative dating Galileo dated his writings only infrequently, PIXE analysis of ink May provide clues toward development of thought and ideas. Un-dated manuscript can be Placed in time and context by PIXE analysis of ink. Hand-made ink showed differences from batch to batch

26 Summary PIXE PIXE is very similar to XRF, the mechanism for exciting the atoms to generate the characteristic X-rays is not based on X- ray irradiation of the sample but on the bombardment with high energy particles typically protons up to 10 MeV. The disadvantage to XRF is, that only small areas can be studied to small depths. For a global study (~cm 2 areas) of the chemical characteristic of a sample XRF is the better method. For the study of mm 2 to mm 2 areas PIXE is the superior approach. Its large advantage to XRF is that two or three dimensional images of the elemental distribution In the sample can be produced with high spatial resolution. Depth profiling is possible within a fairly limited depth range of 0.1mm only. Like in XRF studies the K- and L-transitions of the low to high Z elements are the main signatures.