The feasibility of using portable X-Ray radiography for the

ART CONSERVATION-RESTORATION – STUDIES AND PRACTICE Volume VII VII Conference of Art Conservation-Restoration Students and Graduates Torun 13-15 October 2005 _____________________________________________________________ M. Giannoulaki Department of Conservation of Antiquities & Works of Art, Technological Educational Institution of Athens, Aigaleo, Greece, mgiann@teiath.gr V. Argyropoulos Department of Conservation of Antiquities & Works of Art, Technological Educational Institution of Athens, Aigaleo, Greece, bessie@teiath.gr Th. Panou Department of Radiology, Technological Educational Institution of Athens, Aigaleo, Greece, thpanou@teiath.gr A. Moundrea-Agrafioti Department of History, Archaeology and Social Anthropology, University of Thessaly, Volos, Greece, P. Themelis Society of Messenian Archaeological Studies, Athens, Greece, M. Giannoulaki, V. Argyropoulos, Th. Panou, A. MoundreaAgrafioti, P. Themelis The feasibility of using portable X-Ray radiography for the examination of the technology and the condition of a metals collection housed in the Museum of Ancient Messene, Greece 1. Introduction The collection of metal artifacts from the ancient city of Messene is being studied to determine the problems and needs of a typical archaeological collection in Greece under the auspices of the EC program PROMET. The main objective of the project is to develop a conservation strategy to preserve large metals collections housed in an uncontrolled museum environment. Such a strategy requires the application of scientific techniques in-situ, in order to identify the value and condition of each artifact housed in the museum, so that value-judgments can be taken on which objects are in urgent need of treatment, would benefit from treatment or do not require any treatment. The paper describes one aspect of our approach to apply such a strategy by using X-ray Radiographic analysis to examine an entire collection of metal artifacts, quickly and economically. The collection of ancient Messene includes different types of artifacts made of copper and iron alloys. A small number is on display in the museum of Ancient Messene and the rest of the collection is stored in the museum. The problems one has to deal with are the following: - The objects are catalogued according to their excavation context, but they are not separated according to typological or technological groups. Thus, it is difficult to appreciate the value of the whole collection in terms of ancient metallurgical techniques. - The condition of the artifacts or the collection is unknown. Thus, the real problems of the artifacts and the needs of the whole collection in terms of treatment are unknown. - The storage conditions are partly controlled, resulting in an indoor environment with wide temperature and RH fluctuations during the year. A classification of the artifacts based on their technological characteristics and condition was conducted by visual examination, using Burt frequency tables and around 873 artifacts were selected for further scientific examination. This process was not always easy to apply, since the details of the construction of an object are not always immediately obvious: surface features and decoration may be concealed under layers of corrosion, joins might be internal and sometimes the signs of casting or working can only be found within the metal itself. 1 The iron artifacts from the collection exhibit clear signs of active corrosion (e.g., presence of akageneite and detachment of pieces known as spalling). However, the amount of metal remaining is difficult to ascertain as well as the initial shape or form of the artifact. Artifacts made by copper alloys are both cast and/or hammered, but sometimes it is difficult to distinguish between these two manufacturing techniques by visual inspection alone. Also, some of the artifacts exhibit surface decoration and features, not always visible due to the presence of thick corrosion layers. Finally, it can be difficult by visual inspection alone to determine the actual condition of the objects, when the extent of internal cracks and fissures are hidden underneath the corrosion products. 1. Lang, J, Middleton, A., “Radiography of Cultural Material”, Butterworth Heinemann, England,1997. The metals collection of Ancient Messene cannot be transferred outside of the museum due to the legislation for antiquities in Greece. Thus, any scientific examination must be undertaken in-situ using in our case a portable X-ray radiography system. X-ray radiography is a non-destructive technique, which is often used to reveal hidden clues as to the methods of manufacturing, decorative detail, as well as the overall condition of the artifacts. The application of X-ray Radiography for the examination of cultural heritage objects is a routine and common practice world-wide. However, our literature survey, using the BCIN database (www.bcin.ca) revealed that the application of portable X-radiography systems is not as common. For example, only five references to the use of such a technique were found, but none of them referred to the examination of metal artifacts.2-6 2. Historical and Archaeological Information 2.1 Historical preface The archaeological site of Messene is located at the foot of Mt. Ithome, under the modern village of Ancient Messene of the prefecture of Messenia in Peloponnesus. 7 All the public and sacred buildings and the preserved fortifications have been excavated during four excavation periods, covering an interval of 174 years (1831-today). From 1986 until now, the excavations were led by P. Themelis. Ancient Messene, the new capital of the free and independent Messenia, was founded in 369 B.C. by general Epameinondas from Thebes. 7 2.2. Archaeological and excavation context 2. David, A. R., Tapp, E., “Evidence embalmed: modern medicine and the mummies of Ancient Egypt”, Manchester and Dover: Manchester University Press, 1984. 3. Paderni L., “I raggi x nell’arte” in Conferenza internazionale su le prove non-distruttive nella conservazione delle opera d’arte, Roma, 27-29 Ottobre 1983. International conference on non- destructive testing in conservation of works of art, Proceedings. Roma: Associazione italiana prove non-distruttive / icr, 1983, pp.21.1-21.14 4. Hart, D., “X-ray inspection of historic structures: an aid to dating and structural analyses” in Technology & Conseravtion, Vol. 77, 1977, p. 10-27. 5. Marconi, B., “X-raying pictures: new Polish devices and methods”, in Ochrona zabytków, Vol.1, 1949, pp.25-30. 6. Owen, G., “Use of a portable x-ray machine in archaeological fieldwork”, Cambridge Archaeological Journal, Vol. 3 No.1,1993, pp.134-136. 7. Themelis, P. “The Ancient Messene”, Ministry of Culture, T.A.P.A editions, Athens 2002. The city of Ancient Messene was protected from strong fortification walls. 8 The first monument one encounters on the way from the Museum to the archaeological site is the Theatre. To the east of the Theatre is situated the Agora of Messene. The Asklepieion complex was the centre of the public life. The Stadium and the Gymnasium are among the most impressive and well-preserved building complexes of the site. 3. The Metals Collection The metals collection includes artifacts manufactured from gold, silver, lead, iron and copper alloys, as well as a rich collection of coins. The approximate number of metal artifacts are estimated around 5,000 and 13,000 are coins. Tables 1 and 2 provide a description of the types of copper and iron artifacts studied for this project respectively. Table 1: A description of the types of copper alloy artifacts found in the museum of ancient Messene TOOLSScrapers, spatulas, chisels, medical tools, spades, INSTRUMENTS needles, tongs, quill, ax, hook Simple nails, decorative nails, cringles, parts of locks, ACCESSORIES OF DOORS & keys FURNITURE DECORATIVE Mirrors, buckles, rings, pins, bracelets, earrings, ARTIFACTS necklace VESSELS Small vessels, rims, handles, bases, covers, decorative elements FIGURINESAnimal & Human STATUETTES WEAPONS Spear & arrow shafts, savrotiras, shields Table 2: A description of the types of wrought iron artifacts found in the museum of ancient Messene. WEAPONS Shaft & arrow peaks, savrotiras, daggers, butcher Knives TOOLS-INSTRUMENTS Scrapers, scissors, spatulas, spades, cradles, chisels, knife and 8. Themelis, P., “Ancient Messene. Site and Monuments”, Special edition of the region of Peloponnese, 1998. carving blades, hooks, needles, tongs ACCESSORIES OF DOORS & Simple & decorative nails, cringles, FURNITURE parts of locks, keys, sheathing foils The artifacts come from all the excavated complexes, which form the public sector of the city, as well as from grave monuments of wealthy Messenians. The archaeologists register all the excavated objects in documentation cards and book catalogues, which include general information for each artifact. Until last year, all the metal artifacts were kept in wooden boxes, not separated, in storage rooms with uncontrolled conditions. Last year, the archaeologists moved the artifacts into one of the upper storage rooms (photo 1), where heating systems exist. They had separated the metals and placed each artifact or a group of similar artifacts in polyethylene bags with zip-lock closing. Furthermore, most of the funds are spent in restoration projects of the excavated monuments. Few, if any, metal artifacts undergo treatment. Also, there is a lack of know-how in the proper care of such metals collections. For example, most of the iron artifacts were excavated from wet soil, and were left to dry immediately after excavation. 4. Use of a portable X-Ray radiography system for the examination of the metals collection in Ancient Messene. The curator (archaeologist) of a museum that houses a major metals collection typically confronts the following problems: 1. Difficulty in determining the value of the collection in terms of ancient metallurgical techniques. 2. Difficulty in understanding the actual condition of the artifacts, such as the amount of metal remaining, the presence of internal cracks and fissures, and the extent of corrosion layers. 3. Difficulty in sending out objects for any type of scientific examination without official permission. Thus, the only solution is to provide the application of X-Ray radiography in-situ to answer the relevant problems. Also, such an examination helps the curator to appreciate at a first level the value of the whole collection in terms of technology and the condition of the objects. The present situation of the metals collection in Ancient Messene is typical for most museums in Greece, so that a decision was made to obtain a portable X-ray radiography system, in order to be able to conduct in-situ analysis of the metals collection. We also investigated the option of hiring someone to bring in their own system, but their quote came out to the same as purchasing our own equipment. However, our decision required the cooperation with an experienced and certified radiographer/radiologist, which worked for the TEI of Athens and is an author of this paper. Furthermore, we spent time conducting market research to select a used system that would suit our purposes and be relatively inexpensive. The system chosen is as follows: (photo 2) 1. A second–hand Military control Unit and Tube Transformer Head, X-Ray Apparatus 15 m.A., Mobile-Portable, Stock No. 6-013-680, manufactured by Picker X-Ray Corp., Waite MFG. DIV., Cleveland, Ohio, U.S.A. 2. A portable film processor Curix 60/CP1000, Type 9462, 230V/50/60Hz, manufactured by Agfa-Gevaert N.V., Belgium. The mobile tubestand (1344-D) is packed within a single chest and contains the following items as described in the manual [10]: a. Mobile base assembly. b. Lower mast section. c. Upper mast section. d. Horizontal tube arm assembly. e. Control mounting bracket. f. Crank for actuating vertical carriage. g. Instruction manual. h. Tools and spare parts. The X-Ray source is also packed within a single chest, including the following items: 9,10 a. A radiation cone. b. A shockproof head. c. A hand-timer. d. A head retainer catch. e. F-12 control unit. 9.Anon., Instructions for Military Tubestand X-Ray Apparatus, Mobile-Portable, Stock No. -6169-250, Picker X-Ray Corp., Waite MFG. DIV., Cleveland, Ohio, 1952. 10. Instruction Manual for Military Control Unit and Tube Transformer Head, X-Ray Apparatus 15 M.A., Stock No. 6-013-680, by Picker X-Ray Corp., Waite MFG. DIV., Ohio, 1952. This system was purchased for 1700 Euros. The system could be carried and assembled in-situ, easy, and fast, following the instruction’s manual and with the help of a certified radiologist. The Curix 60 is a film processor developed and manufactured by Agfa (photo 3).11 It is designed for darkroom installation and has been engineered according to the very latest principles. Based on a proven concept, the system has the following advantages: 1. Top quality 2. Low operating costs 3. Simplicity of use 4. Ease of servicing and environmental protection. Exposed film is inserted directly into the feed slot at the left side of the processor. The film passes the film scanner regulating the replenishment and dryer systems, and then passes through the developer, the fixer and the wash-water tanks. After drying, the film leaves the dryer section and is deposited on the exit tray.11 This system was purchased for 4.700 euros and was installed easily in a bathroom, situated next to the storage room where the collection is kept. The bathroom was converted into a dark room for the present situation. The total cost for the purchase of 100 radiographic films 24X30 NIF, 100 radiographic films 35X35 NIF, 12 bottles of developer liquid, 18 bottles of fixer liquid and two radiographic cassettes was 712 Euros. 5. Safety rules According to the manufacturer’s manual, while operating the portable radiography system, all the necessary precautions must be considered, following the recommendations of the National Bureau of Standards and of the International Roentgen Ray Committee on X-Ray protection. Based on our knowledge of Greek law, it is permissible to use the portable X-ray radiography system in areas that are not armored for radiation, because the number of radiographs is much smaller than a regular X-ray radiographic lab and thus exposition parameters –kV, mAs, sec- are particularly low. However, for portable systems the following rules are mandatory: 1. The system must be operated only by a certified user namely a radiologist or a technician radiologist. 11. Curix 60, Reference Manual, Agfa-Gevaert N.V., Belgium 2000. 2. The system must be placed inside a room of the museum, surrounded by walls. 3. The cable for the exposition switch must be at least 10 meters long. 4. The operator is obliged to use a smock sheathed with lead. 5. Care should be taken, so that no people are present in rooms under the floor, when the portable radiography system is in operation. 6. Methodology Over 1000 objects of different shapes and dimensions were examined in two days using the X-ray Radiographic system. This required operating the system 8 hours each day, using 85 radiographic films (dimensions 24X30cm and 35X35cm), 8 bottles of developer liquid, and 5 bottles of fixer liquid. The general operating parameters involved are the following: Distance of the lamp from the radiographic plate: 75cm Correction of voltage of the local line at 70kV. Two radiographic plaques, dimensions 24X30cm and 35X35cm, were used. Objects with big dimensions were placed separately in one single plaque, while small objects of the same type were placed together, as long as they did not present variations in thickness more than 1cm. The objects were placed together with their paper tabs and were photographed with a digital camera, before being X-rayed. As a result, a digital record was created in order to distinguish the objects in each radiographic film (photo 4). 7. Results-Discussion The application of X-ray radiography in the case of the metals collection of Ancient Messene revealed useful information concerning the manufacturing technology and the condition of the artifacts. The following characteristic examples show the utility and the feasibility of the technique. In photos 5-8, the mirrors are presented. The study of the radiographs led to the following observations: 1. All the mirrors were made by casting. One could observe the characteristic porosity, the thickness variations, and a coarse granular appearance or texture that is usually present for cast objects. 2. The light areas are usually indicative of the presence of lead. 3. The dark areas show where the metal is thinner. 4. The extent and the thickness of cracks and fissures are depicted. 5. The techniques used for surface decoration are shown. Another example of the utility of the technique is that of a copper alloy shield dated at the end of 4th-beginning of 3rd c. B.C. (photos 9-11). The shield is covered with soil deposits and corrosion products. The X-radiography revealed the surface inscription and decoration and the manufacturing technique applied, as well as the condition of the shield -cracks, fissures and amount of metal remaining. The radiographs of iron artifacts revealed different information, as one could see through the examples of scissors (photos 12-13) and scrapers (photos 14-15). 1. All iron artifacts are wrought iron. 2. The radiographs revealed the initial shape and form of the artifacts. 3. The condition of the artifacts is clearly shown, since one could observe the amount of metal remaining, as well as the areas where no metal core is retained and the artifacts are mineralized. 8. Conclusions Portable X-ray radiography is a useful and easy technique to apply in-situ. Thus, an entire collection can be examined, and at the same time the objects are safe. With the purchase of a portable film processor one could develop the radiographs fast and easy, in-situ, selecting the operating parameters and achieving better results. The consumables needed for the operation of the system were relatively low. The X-ray radiography gives valuable information for the technology and the condition of the artifacts. The conservator(s) can make the necessary decisions on how to clean and/or stabilize the metal artifacts. With proper training conservators can learn to use such a system. Acknowledgements: The authors would like to thank Amalia Siatou and Stavroula Poulimenea, professional conservators-restorers, for their assistance during the X-raying of the metals collection of Ancient Messene. We also gratefully acknowledge the funding from the EC 6th FF INCO Priority project PROMET to carry out this work. Abstract Most museums in Greece with metals collections cannot undertake the necessary examination of their objects by X-Ray Radiography, because there are limited funds to purchase such an inhouse system, and the laws for the management of cultural heritage in Greece does not allow for removal of museum objects for such analyses without permit. Under the initiative of the European 6th Framework funded project PROMET, the TEI of Athens set up a portable X-Ray Radiographic unit to examine the collection of iron and copper alloy objects from the Museum of Ancient Messene in Greece in-situ. Around 1000 objects were examined using the portable X-Ray radiographic system, in order to distinguish the characteristic technological features and to survey the condition of the artifacts. The paper describes the feasibility of using such a portable system to examine large archaeological collections of metal objects, which is considered a necessary first-step before undertaking conservation treatment. The first step included the purchase of a used Military Tubestand X-Ray Apparatus. The results in terms of determining the amount of metal remaining and impression of details of the objects were very good. Thus, it was considered necessary to make the radiography system more feasible, by also developing the films in-situ, which involved the purchase of a portable film processor. The film processor cost around 4.700 Euros. Examining over 1000 objects of different shapes and dimensions in two days required operating the system 8 hours each day. The total cost of the supplies was around 400 Euros. The portable radiography system worked well in examining all the metal objects from Ancient Messene. The examination was considered essential so that the conservator(s) can make the necessary decisions on how to clean and/or stabilize the metal artifacts. Keywords: metal collection, Ancient Messene, copper and iron alloys, portable X-ray radiography, film processor. Photo 1: View of storage room. Photo 2: The portable film processor. Photo 3: The portable X-ray radiographer. Photo 4: Radiography plaque 35X35 with nails. Photo 5: Simple circular mirror (2nd c. B.C.). Photo 6: X-Radiography (85kV, 30mAs,3sec). The radiograph depicts the cast structure, the extent and thickness of cracks and fissures. The light areas are probably lead. Photo 7: Simple circular mirror probably tin-plated (2nd c. B.C.) Photo 8: X-Radiography (80kV, 25mAs, 2.5sec). The radiograph depicts the cast structure, the extent and thickness of cracks and fissures. The light areas are probably lead. The dark areas show where the metal is thinner. Photo 9: Shield from copper alloy. Photo 10: X-Radiography (65kV, 10mAs, 1sec). The radiograph depicts the condition of the object: white areas indicate presence of metal core, grey areas indicate corrosion products and black areas absence of metal. Photo 11: XRadiography of hammered decoration depicting a floral motive (65kV, 10mAs, 1sec). Photo 12: Iron scissors. Photo 13: X-Radiography (55kV, 10mAs, 1sec).White areas indicate presence of metal core, grey areas indicate corrosion products and black areas absence of metal. Photo 14: Scraper. Photo 15: X-Radiography (55kV, 10mAs, 1sec). White areas indicate presence of metal core, grey areas indicate corrosion products and black areas absence of metal.