Conservation and restoration of copper-based objects
The conservation and restoration of copper and copper-alloy objects is the preservation and protection of objects of historical and personal value made from
Historically, objects made from copper or copper alloy were created for religious, artistic, technical, military, and domestic uses. The act of
History
Copper Age
Copper occurs naturally as
Bronze Age
Alloying copper with tin to make bronze was first practiced about 4000 years after the discovery of copper smelting, and about 2000 years after "natural bronze" had come into general use. Bronze artifacts from Sumerian cities and Egyptian artifacts of copper and bronze alloys date to 3000 BC.[10] The Bronze Age began in Southeastern Europe around 3700–3300 BC, in Northwestern Europe about 2500 BC. It ended with the beginning of the Iron Age, 2000–1000 BC in the Near East, 600 BC in Northern Europe. The transition between the Neolithic period and the Bronze Age was formerly termed the Chalcolithic period (copper-stone), with copper tools being used with stone tools. This term has gradually fallen out of favor because in some parts of the world the Calcholithic and Neolithic are coterminous at both ends. Brass, an alloy of copper and zinc, is of much more recent origin. It was known to the Greeks, but became a significant supplement to bronze during the Roman Empire.[10]
Antiquity and Middle Ages
In Greece, copper was known by the name chalkos (χαλκός). It was an important resource for the Romans, Greeks and other ancient peoples. In Roman times, it was known as aes Cyprium, aes being the generic Latin term for copper alloys and Cyprium from
Britain's first use of brass occurred around the 3rd–2nd century BC. In North America, copper mining began with marginal workings by Native Americans. Native copper is known to have been extracted from sites on Isle Royale with primitive stone tools between 800 and 1600.[12] Copper metallurgy was flourishing in South America, particularly in Peru around 1000 AD; it proceeded at a much slower rate on other continents. Copper burial ornamentals from the 15th century have been uncovered, but the metal's commercial production did not start until the early 20th century.
The cultural role of copper has been important, particularly in currency. Romans in the 6th through 3rd centuries BC used copper lumps as money. At first, the copper itself was valued, but gradually the shape and look of the copper became more important. Julius Caesar had his own coins made from brass, while Octavianus Augustus Caesar's coins were made from Cu-Pb-Sn alloys. With an estimated annual output of around 15,000 t, Roman copper mining and smelting activities reached a scale unsurpassed until the time of the Industrial Revolution; the provinces most intensely mined were those of Hispania, Cyprus and in Central Europe.[13][14]
The gates of the
Modern period
The
The uses of copper in art were not limited to currency: it was used by
The Intergovernmental Council of Copper Exporting Countries, formed in 1967 with Chile, Peru, Zaire and Zambia, played a similar role for copper as OPEC does for oil. It never achieved the same influence, particularly because the second-largest producer, the United States, was never a member; it was dissolved in 1988.[22]
Conservation
Historical objects
Documentation
Systematic and well-managed documentation is today an essential prerequisite for quality executed conservation and restoration treatments, including documentation of the state of objects before, during and after treatment. Identification of materials and procedures used to produce object and the results of any scientific research must be part of documentation too. Last but not least, an integral part of the documentation must be a recommendation for further care of object.
Research
- identification of metals, alloys and metallic coatings
- identification of other organic/inorganic materials
- identification of corrosion products and processes
- identification of technology used to produce object
Cleaning
Chemical | Electrochemical | Mechanical | Ultrasonic | Laser | Plasma |
---|---|---|---|---|---|
Ammonium citrate 5% / pH 9[23]
Citric acid 20% + 4% thiourea[24] Phosphoric acid 10–20% + 1% thiourea[24] EDTA 4% pH 10[24] Potassium sodium tartarate 25% NaOH 120 g/40 g glycerol/1 L water[24] Polymethacrylic acid 10–15% pH 4.5–5.5[25] |
NaOH 2–5%, stainless steel anodes + Ecorr measurement! | Precipitated chalk/water mixture
scalpel micromotor and steel/or bristle brushes microsanblasting unit dry ice blasting |
4-6 g sodium carbonate /6–8 g sodium phosphate
10-12 g sodium metasilicate 1 L distilled water 2–5 minutes, then rinse well and repeat if needs |
Can be used[26] | Can be used[29][30] |
Consolidation
Stabilization
Protective coatings
- clearcoats - Paraloid B-72 - Incralac - Ormocer - Everbrite Coating - Pantarol A
- waxes - Renaissance Wax - Cosmolloid 80 H - Dinitrol 4010 - Poligen ES 91 009
- combinations - Paraloid B-72 + topcoat Renaissance Wax etc.
Archaeology objects
Documentation
Research
Decision making
Cleaning
- mechanical
-Microsandblasting
-Dry ice blasting
-Scalpel or scraper
High speed micromotor
-Steel or ceramic burs and cutters
-Abrasive wheels
-Wire brushes
-Glass fibre brushes and pens
-Setting hammer
Consolidation
Stabilization
- chloride removal
- corrosion inhibitors
-4 methyl imidazole[32]
-ammonium sulphide[34]
Protective coatings
- clearcoats - Paraloid B-72 - Incralac - Ormocer - Everbrite Coating - Pantarol A
- waxes - Renaissance Wax - Cosmolloid 80 H - Dinitrol 4010 - Poligen ES 91 009
- combinations - Paraloid B-72 + topcoat Renaissance Wax etc.
Preventive conservation
The items should be stored in rooms that are protected from polluted air, dust, ultraviolet radiation, and excessive relative humidity – ideal values are temperature of 16–20 °C and up to 40% (35–55% according to recent Canadian Conservation Institute recommendations) relative humidity, noting that if metal is combined with organic materials, relative humidity should not be below 45%. Archaeological objects must be stored in rooms (or plastic boxes) with very low relative humidity, or in the case of particularly valuable items in the chambers with nitrogen or argon. Copper or copper alloy objects with active corrosion up to 35% RH. Shelves in the storerooms must be of stainless steel or chlorine and acetate free plastic or powder coated steel. Wood and wood based products (particle board, plywood) must be avoided. Also do not use rubber, felt or wool. When you are handling metal objects, always wear clean cotton gloves . Lighting levels must be kept below 300 lux (up to 150 lux in case of lacquered or painted objects, up to 50 lux in case of objects with light sensitive materials).
See also
- Conservation and restoration of metals
- Conservation and restoration of ferrous objects
- Conservation and restoration of glass objects
- Conservation and restoration of ivory objects
- Conservation and restoration of ceramic objects
- Conservation and restoration of silver objects
References
- ^ a b "CSA – Discovery Guides, A Brief History of Copper". Csa.com. Archived from the original on 2015-02-03. Retrieved 2008-09-12.
- ISBN 0-313-33507-9.
- ^ "Copper". Elements.vanderkrogt.net. Retrieved 2008-09-12.
- ISBN 978-0-14-013642-5. Retrieved 21 December 2011.
- ^ Cowen, R. "Essays on Geology, History, and People, Chapter 3: "Fire and Metals: Copper". Retrieved 2009-07-07.
- .
- ^ a b "CSA – Discovery Guides, A Brief History of Copper". CSA Discovery Guides. Archived from the original on 3 February 2015. Retrieved 29 April 2011.
- ^ Pleger, Thomas C. "A Brief Introduction to the Old Copper Complex of the Western Great Lakes: 4000–1000 BC", Proceedings of the Twenty-Seventh Annual Meeting of the Forest History Association of Wisconsin, Oconto, Wisconsin, October 5, 2002, pp. 10–18.
- ISBN 1-4384-2701-8.
- ^ ISBN 0-203-19211-7.
- JSTOR 2843960.
- ^ Martin, Susan R. (1995). "The State of Our Knowledge About Ancient Copper Mining in Michigan". The Michigan Archaeologist. 41 (2–3): 119. Archived from the original on 2016-02-07. Retrieved 2012-12-11.
- .
- ^ de Callataÿ, François (2005). "The Graeco-Roman Economy in the Super Long-Run: Lead, Copper, and Shipwrecks". Journal of Roman Archaeology. 18: 361–372 (366–369).
- doi:10.1021/ma9904870. Archived from the original(PDF) on 2007-09-29.
- ^ "World Mysteries – Strange Artifacts, Baghdad Battery". World-Mysteries.com. Archived from the original on 5 May 2011. Retrieved 22 April 2011.
- ISBN 978-1-86189-173-0.
- ^ "Gold: prices, facts, figures and research: A brief history of money". Retrieved 22 April 2011.
- ^ "Copper History". Retrieved 2008-09-04.
- .
- ^ "Outokumpu Flash Smelting" (PDF). Outokumpu. p. 2. Archived from the original on July 24, 2011.
{{cite web}}
: CS1 maint: bot: original URL status unknown (link) - .
- ^ H.Brinch-Madsen, "Die reinigung von eisen mit ammoniakalischer Citronensaure", Arbeitsblatter fur Restauratoren 2/1974
- ^ a b c d Stambolov, T.;Eichelmann, N.;Bleck, R.D. Korrosion u nd Konservierung von Kunst und Kulturgut aus Metall / I, Weimar 1987.
- ^ Nikitin, M.K.;Melynikova, E.P. Himiya v restavracii, Leningrad 1990.
- ^ 1.Cooper, M.I. (2002) Laser cleaning of metal surfaces: an overview. Paper presented at the UKIC Metals Section ‘Back to Basics: Surface Treatments’ conference (Liverpool, October 1999). Published in 'Back to Basics, The Metals Section' Press, 34-39.
- ^ Siano, S. The Gate of Paradise: physical optimization of the laser cleaning approach, Studies in Conservation 46/ 2001.
- ^ Drakaki, E. et al. Evaluation of laser cleaning of ancient Greek, Roman and Byzantine coins, Surface and Interface Analysis, 42(6-7), 671 - 674., 2010.
- ^ Saettone, E.A.O., Matta, J.A.S., Alva, W., Chubaci, J.F.O., Fantini, M.C.A., Galvão, R.M.O., Kiyohara, P. and Tabacniks, M.H., 2003. Plasma cleaning and analysis of archaeological artefacts from Sipán. Journal of Physics D: Applied Physics 36: 842-848. Accessed 13.02.2015.
- ^ http://www.plasmaconservation.cz/soubory/2012/prednaska-pppt-2012-krcma.ppt Accessed 13.02.2015.
- ^ Stambolov,T.;Bleck,R.D.;Eichelmann,N. Korrosion und Konservierung von Kunst und Kulturgut aus Metall,Weimar I/1987.,II/1988
- ^ http://www.medal-project.eu/11-Copper_conservation.swf[permanent dead link]
- ^ Schemahanskaya,M.S.;Lemenovskiy,D.A.;Lomonosova,M.V.;Nesmeyanova,A.N.;Brusova,G.P Novie metodi v restavracii archeologicheskogo metala,Vestnik restavracii muzeinih cenostei 1/11,Moscow 2008.
- ^ Belkin A.P.,Nackiy M.V. Metod obrabotki ochagov "bronzovoi bolezni" mednih splavov sulfidami amoniya//Restavracija pamjatnikov istorii i kulturi/GEL,Informkultura/Ekspres-informacija.Moscow,1987.Bp. 3. -S.6-8
Further reading
Books
- Selwyn, L. Metals and Corrosion - A Handbook for the Conservation Professional, Ottawa 2004.
- Scott, D.A. Metallography and Microstructure of Ancient and Historic Metals, Santa Monica 1991.(online)
- Scott, D.A. Ancient and Historic Metals - Conservation and Scientific Research, Santa Monica 1994.(online)
- Scott, D.A. Copper and Bronze in Art - Corrosion, Colorants, Conservation, Los Angeles 2002.(online)
- Cronyn, J.M. The Elements of Archaeological Conservation, London 1990.
- Rodgers, B. The Archaeologist Manual for Conservation - A Guide to Non-toxic, Minimal Intervention Artifact Stabilization, New York 2004.
- La Niece,S. and Craddock,P. Metal Plating and Patination: Cultural, Technical and Historical Developments, Boston 1993.