To Keep the Patina, or Not to Keep the Patina…
To Keep the Patina, or Not to Keep the Patina…
Patina is a natural layer of corrosion that appears on the surface of various types of metals, including copper, bronze, and brass (Ankersmit 2013). This layer is stable and uniformed across the surface of the object, unlike other types of corrosion products which can be bulky and localized. It provides protection from other environmental degradation processes and slows further corrosion of the metal (Caple 2000). Although patina provides these benefits, it can appear on the surface of brass as a brown coating, hiding the lustrous metal below. Therefore, should the layer of patina remain when conserving the object, or should the patina be removed to reveal the true nature of the metal? As conservators, we are continually faced with these types of difficult ethical and theoretical issues. In order to make the most informed decision, a conservator must weigh the benefits and downfalls of the layer of patina on a case-by-case basis.
Patina can be preserved on objects because of its protective qualities and aesthetically pleasing aged appearance. Metal objects are subject to corrosion processes, such as humidity, rain, and air pollutants (Curkovic 2010). Therefore, it is not uncommon for artists and conservators to replicate the process of patination, by accelerating the corrosion using various chemicals. In addition to its functional value, the benefits of patinas are also apparent from an aesthetic point of view. Brandi (1996) states, “Historically we have seen that the patina documents the passage through time of the work of art and thus needs to be preserved” (378). The brown layer of patina gives the object an aged appearance that is consistent with other antiques, which has implications towards the object’s aesthetic, historical, and even monetary value. Thus, these benefits of the patina layer on objects can make a case for the justification of its preservation.
Image 1: Apollo as an Archer (Apollo Saettante), a bronze Roman statue, dating to 100 B.C.–before A.D. 79, featuring an exterior layer of patina. http://www.getty.edu/art/exhibitions/apollo_pompeii/
On the contrary, it can be argued that the mere presence of a brown patina layer inhibits the true nature and appearance of the metal below. According to Caple (2000), “The true nature of an object includes evidence of its origins, its original construction, the materials of which it is composed and information as to the technology used in its manufacture” (62). It is further stated in the process of conservation, it is desirable “to move towards revealing the truth(s) about an object and away from the obstruction of dirt, decay, or inaccurate and inappropriate restoration” (Caple 2000:62). Most brass metal objects displayed a lustrous surface when they were originally constructed. Taking this into consideration, the matte appearance of patina is not consistent with the true nature of the metal. This perspectives provides a justification for the removal of the patina.
Image 2: Polished brass (left) and tarnished brass (right). https://www.cci-icc.gc.ca/caringfor-prendresoindes/articles/metals-metaux/index-eng.aspx
Conservators are frequently faced with ethical and theatrical issues that require them to make judgments and decisions towards the treatment of object. These choices are based off of personal experience, current trends in conservation, and weighing the positive and negative factors associated with such treatments (Caple 2000). When making a decision on whether or not to preserve the patina, conservators should consider the object’s historical significance, aesthetic value, original function, current state of preservation, future display location, and true nature. Some of these factors represent conflicting viewpoints, but it is the delicate balance between such factors in addition to preserving and maintaining the longevity of an object that provides the foundation for a holistic, effective, and appropriate conservation treatment.
Ankersmit, Bart, Martina Griesser-Stermscheg, Lyndsie Selwyn, and Susanne Sutherland. 2013. Recognizing Metals and their Corrosion Products. Canadian Conservation Institute. https://www.cci-icc.gc.ca/caringfor-prendresoindes/articles/metals-metaux/index-eng.aspx
Brandi, C. 1996. Theory of Restoration, Part III. In Historical and Philosophical Issues in Conservation of Cultural Heritage. Pp. 377-379.
Caple, Chris. 2000. Conservation Skills: Judgment, Method and Decision Making. New York: Routledge.
Curkovic, H.O., T. Kosec, A. Legat, and E. Stupnisek-Lisac. 2010. Improvement of corrosion stability of patinated bronze. Corrosion Engineering, Science and Technology 45(5):327-333.