Bronze Seminar Course Outline

I. Lectures

   1. Bronze and the foundry
   2. Bronze and the environment  
   3. Common conditions, repair and cleaning  
   4. Protection, reintegration and maintenance  
   5. Planning, support, management and evaluation  

II.Resource and Reading Lists

   1. Conservation information and suppliers  
   2. Bibliography  

I. Lectures

 1. Bronze and the foundry

 I. Introduction  
  What we'll cover: Outdoor metals, concentrate on cast bronze  
 II. What is bronze?  
  What is a metal? What is an alloy?  
 III. Where do bronzes come from?  
 IV. Bronze Casting  
  Casting defined  
 V. Casting Methods  
 VI. Misruns, etc.  
 VII. Finishing  
 VIII. Patination  
  Effects, traditional methods, gilding, paint, etc.
Further reading and references
Surface coatings
 IX. Microstructure  
  Casting and solidification
Three zones of solidification
Phase equilibrium diagram
Galvanic series
Archaeological examples
 X. Summary  

Back to Top

2. Bronze and the environment

 I. Introduction - Bronze and the environment  
  A. What do we really need to know here?
B. Bronzes corrode in the environment and it's our job to stop them. I'm going to show you how the environment interacts with bronze (and copper). 
 II. Defining terms  

A. Let's start by falling back on the oldest crutch for lecturers - defining terms: Bronze-: environment

  a) Pure air
b) Moisture
c) Air pollution
d) Acid rain
e) Human and animal agencies
f) Environmental types
g) Corrosion

B. A bronze in the environment

III. What's happening?  
IV. Electrochemical nature of corrosion  
V. Corrosion of high-tin alloys  
VI. Cross-sections  
VII. Corrosion rates  
VIII. Pollutants  
IX. Questions of dry deposition and corrosion: time of wetness, dissolved species, runoff studies  
X. How to stop corrosion?  

A. Corrosion requires

  1. Active substrate
2. Oxygen
3. Pollutants
4. Water - moisture

B. An Example of the Efficacy of Surface Coatings

 XI. Conclusion  

Back to Top

3. Common conditions, repair and cleaning

  The care of public art is a public concern and can only succeed with public support.  
 I. Common conditions : weathered structures and finishes  

For outdoor bronzes, the most common aesthetic problem is that a weathered patina prevents us from clearly seeing details of modelled shapes and textures.

A. Minor repair

B. Examples of conditions commonly observed


1. Human and animal effects

2. Failure of coatings

3. Corrosion effects

4. Recrystallized investment

5. Mineral deposits


 II. Minor repairs to stablize intact sculpture  
 III. Cleaning  

Often the first step in treatment is cleaning.

A. Dry methods

B. Aqueous systems

C. Non-aqueous or mixed systems

After cleaning, bronze surfaces may need reintegration and protection, our topics in the next lecture


Back to Top

4. Protection, reintegration and maintenance


Protection and reintegration are often accomplished simultaneously. This is especially true for minimal intervention methods using accessible technology.

The goal of reintegration is usually to reduce contrasts between dark and light, by unifying surface colors and imparting a smooth finish.

Coatings of lacquer or of wax can be effective both for protection against corrosion factors moisture and acidic deposition, and for reintegration by the coatings' visually saturating effects on color and texture.

A. Clarification and refinement of subtle and obvious features


1. Form, texture and reflection

2. Color and contrast


B. Coatings


1. When not to coat

2. Coating types and functions
  a. Lacquers
b. Wax

3. Passive or minimal conservation


a. Primacy of aesthetics and commemoration

b. Decisions depend on appearances and tastes

c. The treatment(s) cycle: the bad with the good




Adequate provision for maintenance preserves both sculpture and the resources expended in producing or restoring sculpture.

A. Periodic scheduled examination and upkeep

B. Cleaning and recoating for maintenance

C. Deteriorated coatings


Back to Top

5. Planning, support, management and evaluation


To be effective we have to begin every project with careful planning, follow through with good management at all times, and evaluate what we accomplish.

Projects to conserve intact sculptures may fit a general structure, from planning and support to management, reporting and evaluation.

 I. Plan and support the project  

A.Investigate the sculpture/monument
  1. Identify
2. Survey and assess
 i. Determine access
ii. Research original structure, fabrication and finish
iii.Document observed strucuture and finish
iv. Research and document local environmental and cultural factors

B. Develope project plans and support
  1. Prepare plan in written and spoken forms
2. Present the plan for approval and support

 II. Manage the project  

Every effective effort or project is managed according to a plan.

A. Budget for and obtain resources

B. Organize and carry out field operations

C. Report and evaluate the project


Back to Top

II.Resource and Reading Lists

1. Conservation information and suppliers

Our non-comprehensive list of mostly online resources, in the following subcategories:

  • Information
  • History
  • Conservation and closely related organizations
  • Professional literature / Publications
  • Safety
  • Funding
  • Suppliers
      Art/ craft/ chemical supplies & materials
    Conservation specialty supplies
    Acrylic lacquer coatings
    Metal leaf
    Moldmaking elastic resins
    Safety equipment
    Tools and equipment (comprehensive)

Back to Top

2. Bibliography

To recommend publications in any language, please send citations and abstracts to

Conservation and conservation science

1. Baboian, Robert, E. Blaine Cliver, and E. Lawrence Bellante, eds. The Statue of Liberty Restoration - (Proceedings of The Statue of Liberty - Today for Tomorrow Conference in New York). Houston, Texas: National Association of Corrosion Engineers, 1990.

2. Chase, W.T. Bronze Disease and Its Treatment (Catalogue of an Exhibition at the Thai National Museum). Bangkok, Thailand: Thai National Department of Antiquities, 1974.

3. Chase, W. T., and Nicolas F. Veloz. "Abrasive Cleaning of Statuary & Other Structures: A Century of Technical Examination of Blasting Procedures." Technology and Conservation 10.1 (1989):18-28.

4. Dolcini, Loretta, ed. Verrocchio's Christ and St. Thomas a masterpiece of sculpture from Renaissance Florence. (includes excellent technical studies) New York, N.Y: The Metropolitan Museum of Art/ Abrams; 1992.

5. Drayman-Weisser, Terry ed. Dialogue 89 - The Conservation of Bronze Sculpture in the Outdoor Environment: A Dialogue Among Conservators, Curators, Environmental Scientists and Corrosion Engineers (Johns Hopkins University, Baltimore, MD). Houston, TX: National Association of Corrosion Engineers, 1992.

6. Graedel, T. E., and T. Drayman-Weisser. Glossary on Historic and Artistic Metals. Houston, Tex.: NACE, 1989.

7. ICCROM (International Center for Conservation in Rome) Conservation of Metal Statuary and Architectural Decoration in Open-Air Exposure (Paris meeting), Rome: ICCROM (International Center for Conservation in Rome), 1987.

8. Koller, Johann, and Ursula Baumer. "Organische Überzüge Auf Metallen. Teil 2, Wachse Und Emulsionen (Organic Coatings on Metals. Part 2; Waxes and Emulsions)". Arbeitsblatter Fur Restauratoren. Gruppe 19. Naturwissenschaftliche Untersuchungen 33.2 (2000): 227-41.

9. Letardi, Paola. "Electrochemical impedance measurements in the conservation of metals", in: Radiation in Art and Archeometry. D.C. Creagh and D.A. Bradley, eds., New York: Elsevier Science, 2000.

10. ____, A. Beccaria, M. Marabelli, G. D'Ercoli. "Characterization of bronze corrosion and protection by contact probe measurements", presentado en el congreso mundial del ICOM-CC Grupo de trabajo de metal: "Metal 2001", 2-6 abril, 2001 a la Universidad de Chile, Santiago de Chile, Chile.

Back to Top

11. ____, M. Marabelli, G. D'Ercoli. "Protective coating systems for outdoor sculpture: weathering tests in marine environment", presented in the international symposium: "Exposure 2001", 7-10 November, 2001 at the Institut fur Restaurierung, Hildesheim, Germany.

12. Lindley, P. Sculpture Conservation: Preservation or Interference? Aldershot, Hants, UK: Scholar Press, 1997.

13. Lins, Andrew, and Tracy Power. "The Corrosion of Bronze Monuments in Polluted Urban Sites: A Report on the Stability of Copper Mineral Species at Different pH Levels". Ancient and Historic Metals: Conservation and Scientific Research. Eds. David A. Podany Jerry Consadine Brian B. Scott. Marina del Rey, CA: J. Paul Getty Museum and the Getty Conservation Institute, 1993, 119-52.

14. Meissner, Birgit, Anke Doktor, and Martin Mach, eds. Bronze- Und Galvanoplastik: Geschichte -- Matreialanalyse -- Restaurierung. Arbeitsheft 5. Dresden: Landesamter für Denkmalpflege Sachsen und Sachsen-Anhalt, 2000.

15. Merk-Gould, L., R. Herskovitz and C. Wilson. "Field tests on removing corrosion from outdoor bronze sculptures using medium pressure water." Journal of the American Institute for Conservation 37.2, (1998).

16. Naudé, Virginia Norton, ed. Sculptural Monuments in an Outdoor Environment, Philadelphia: Pennsylvania Academy of the Fine Arts, 1985.

17. Naudé, Virginia Norton, and Glen Wharton. Guide to the Maintenance of Outdoor Sculpture. Washington, DC: American Institute for Conservation of Historic and Artistic Works, 1993-1995.

18. Naylor, Andrew. "Modern Conservation of Outdoor Bronze Sculpture". Monuments and the Millennium: Proceedings of a Joint Conference Organized by English Heritage and the United Kingdom Institute for Conservation: London: English Heritage, 2000. 91-96.

19. Pourbaix, Marcel. "Electrochemical Corrosion and Reduction". Corrosion and Metal Artifacts - A Dialogue Between Conservators and Archaeologists and Corrosion Scientists: Gaithersburg, MD, USA. eds. B. Floyd Brown, et al. Washington, D.C.: National Bureau of Standards, 1977.1-16.

20. Price, C., D. Hallam, J. Ashton, G. Heath, D. Creagh. "An Electrochemical Study of Waxes for Bronze Sculpture," ICOM-CC Metals Working Group international conference Metals `95, September 25-28, 1995 in Semur-en-Auxois, France.

Back to Top

21. Robbiola, Luc, Christian Fiaud, and Stephane Pennec. "New Model of Outdoor Bronze Corrosion and Its Implications for Conservation". ICOM Committee for Conservation Tenth Triennial Meeting, Washington, DC, 22-27 August 1993; Preprints: Washington, DC. ed. Janet Bridgland. Paris: ICOM Committee for Conservation, 1993. 796-802.

22. Roemich, Hannelore, ed. New Conservation Methods for Outdoor Bronze Sculptures, EUR 16637 EN, Directorate-General XII, Science, Research and Development. Luxembourg: Office for Official Publications of the European Communities, 1996.

23. Save Outdoor Sculpture!. A Video Guide for the SOS! Volunteers; Business and Community Partnerships; Legacy at Risk!; SOS! Adopt-a-Sculpture Kit; SOS! Fund-Raising Kit; SOS! Maintenance Information Kit, Washington, DC: National Institute for the Conservation of Cultural Property, 1992,1994,1996.

24. Scarfî, Bianca Maria ed. The Lion of Venice - Studies and Research on the Bronze Statue in the Piazzetta. Venice: Albrizzi Editore of Marsilio Editori, 1990.

25. Scott, David A. Copper and Bronze in Art. Los Angeles: The Getty Conservation Institute, 2002.

26. Scott, John. "The care of outdoor bronzes in North America", presented in the international symposium: "Exposure 2001", 7-10 November, 2001 at the Institut fur Restaurierung, Hildesheim, Germany

27. ____, compiler. Literature and resource compilations for participants in introductory seminars on the conservation of outdoor bronze sculpture. New York, NY: New York Conservation Foundation.

28. Strandberg, Helena. Perspectives on Bronze Sculpture Conservation: Modeling Copper and Bronze Corrosion Göteborg : Göteborg University, 1997.

29. Sturman, Shelley, Julie Unruh, and Helen Spande. Maintenance of Outdoor Sculpture: An Annotated Bibliography. Washington, DC: National Institute for the Conservation of Cultural Property (now Heritage Preservation) 1996.

30. Veloz, Nicolas F. "Development and Implementation of a New Method of Wax Application for Outdoor Sculpture Using Airless Sprayer". Objects Specialty Group Postprints: (AIC, Norfolk, Virginia).compilers Virginia Greene and John Griswold. Washington, DC: The American Institute for Conservation, 1996.23-33.

Back to Top

31. ____, A. W. Ruff, and W. T. Chase. "Practical Aspects of Using Walnut Shells for Cleaning Outdoor Sculpture" and "Successful Use of Soft Abrasives (Walnut Shells) for Cleaning Outdoor Bronze Sculpture by Air Jets". Association for Preservation Technology Bulletin 25.3/4 (1994):70-76.

32. Weil, Phoebe D. "The Conservation of Outdoor Bronze Sculpture: A Review of Modern Theory and Practice", in Brown, B. Floyd, et al. Corrosion and Metal Artifacts - A Dialogue Between Conservators and Archaeologists and Corrosion Scientists: Gaithersburg, MD, Washington, D.C.: National Bureau of Standards, 1977.

33. Wilton-Ely, John, and Valerie Wilton-Ely. The Horses of San Marco, includes technical study. Venice. London: Thames and Hudson, 1979.
General Science

34. Cotton, William P. "Waxes". Kirk-Othmer Encyclopedia of Chemical Technology. in. ed. Mary Howe-Grant. Fourth Edition ed. Vol. 25. New York: John Wiley & Sons, 1998. 614-26.

35. Franey, J. P., Graedel, Thomas E., et al. Corrosion Science - Special Issue on Copper Patina Formation 27.1 (1987)

36. Phipps, P. Beverly P., and D. W. Rice. "The Role of Water in Atmospheric Corrosion". Corrosion Chemistry: ACS Symposium Series. Chicago. eds. George R. Brubaker and P. Beverly P. Phipps. Washington, D.C.: American Chemical Society, 1979. Chapter 8, 235-61.

37. Pourbaix, Marcel. Lectures on Electrochemical Corrosion. New York: Plenum Press, 1973.

Back to Top

Art methods and materials

38. Andrews, Oliver. Living materials-A Sculptor's Handbook. Berkeley: University of California Press, 1983-1988.

39. Birks, Tony. The Alchemy of Sculpture. Marston Magna, Yeovil, Somerset and Chalford, Gloucestershire: Marston House and Pangolin Editions, 1998.

40. Hauser, Christian. Art Foundry - Craft and Art. New York: Van Nostrand, 1972.

41. Metropolitan Museum of Art. Handbook No. 7: Sculptural Plaster Casts and Bronze Reproductions. New York: Metropolitan Museum of Art.

42. Young, R. D. and Fennell, R. A.. Methods for Modern Sculptors. San Rafael, CA: Sculpt-Nouveau, 1980.

Back to Top


43. Cohen, Michelle and Gayle, Margot. The Art Commission and the Municipal Art Society Guide to Manhattan's Outdoor Sculpture. New York: Prentice Hall Press, 1988.

44. Elsen, Albert E. Rodin's Thinker and the Dilemmas of Modern Public Sculpture. New Haven: Yale University Press, 1985.

45. Gillis, John R. ed. Commemorations - The Politics of National Identity. Princeton: Princeton University Press, 1994.

46. Gómez, Hernán F. Monumentos y lugares históricos de Corrientes. Buenos Aires: Talleres gráficos "San Pablo", 1942.

47. Senie, Harriet F. Contemporary Public Sculpture: Tradition, Transformation, and Controversy. New York and Oxford: Oxford University Press, 1992.

48. Shapiro, Michael Edward. Bronze Casting and American Sculpture 1850-1900. Newark, Delaware: University of Delaware Press/ Associated University Presses, Inc., 1985.

Back to Top