Phoebe Dent Weil
Northern Light Studio, LLC
This paper reviews the evolving meaning of the term patina and shows how the use of the word is reflected in changing attitudes towards corrosion, surface coloration of works of art and conservation treatment of bronze sculpture.
Patina is an Italian term that has been freely borrowed into other languages: for example the German Patina, the French word patine, and the English form where it is written patina, but typically pronounced pa-ti’-na. Its current usage is, as it has been from its earliest traceable meaning, broad and inclusive rather than narrowly scientific and precise. It can refer in the, widest sense to the effects of time, weathering, accumulation of particulate matter, corrosion and use, and normally implies a positive or desirable aspect of these changes. For the conservation of works of art, and here, for our discussion of the conservation of outdoor bronze sculpture, the notion of patina in its broadest sense presents a problem, the irony of which should be immediately apparent: if the goal of conservation is to prevent change, to determine the causes and effects of change, and to counteract those changes, when, if ever, can patina be considered valuable? Is there such a thing as “good patina”? What are the aesthetic requirements for judging a good patina as distinguished from one that is deleterious? Or, in reference to the special case of sculpture, how have sculptors dealt with the problem of form in relation to color?1
The case of patina as the word has been used in reference to outdoor bronze sculpture has presented specific and complex problems for interpretation and preservation from antiquity to the present day.2 Part of the problem lies in the high reactivity of the freshly exposed copper alloy surface which, even in indoor conditions, quickly alters, acquiring a tarnish and is highly vulnerable to staining and discoloration in contact with airborne pollutants, and especially to water or other liquids. The artistic process of the sculptor and also the aesthetic enjoyment of looking at sculpture has always necessarily included some form of surface treatment to enhance and complement visual reading of the forms, and also necessarily to perform the task of stabilization and protection of the vulnerable raw bronze surface, the latter function being particularly significant for bronzes under aggressive outdoor conditions where random discoloration of the surfaces typically disfigure and interfere with the visual reading of the sculptural forms and surface textures. Significantly, the discolorations represent the formation of corrosion products that are formed at the expense of the underlying metal and represent an irreversible physical loss.
The peculiar characteristic of bronze to form a wide range of colored corrosion products early on inspired wonder and curiosity in manipulating the metal exposing it to different reagents and exploring potential uses for the results, most of which were medicinal or cosmetic, and which had the effect ultimately of stimulating the development of the field of chemistry.3 Cyril Smith has cited this development as a good example of scientific discovery motivated by aesthetic curiosity,4 and Forbes has pointed out the origin of the word “chemistry” is found in the ancient Greek chyma meaning “casting”.5
In the ancient world prevailing aesthetic notions regarding surface coloration and strategy for protection of surfaces of bronze sculpture were quite different from what they are today. Because the surfaces of all ancient bronzes, with few exceptions, have corroded and altered under conditions of burial, submersion in sea water, or outdoor exposure, there are almost none that provide us with a well preserved indication of their original appearance. The typical azurite and malachite corrosion that has formed on these bronzes can be immensely appealing in color which has been admired as a thing of beauty in itself having been formed over a long period of time and as a result of natural processes outside and beyond the intentions of the original fabricator. Early speculation about these pieces included the possibility that the green or blue appearance might have been intentional. As more ancient bronzes have been discovered and carefully studied, the physical evidence together with interpretation of the written documentation have become increasingly persuasive that ancient bronze sculpture was polished and the gleaming golden surfaces were adorned with inlays for both ornamentation and naturalistic coloration effects produced from a variety of materials.6 These might include reddish copper, for example, to represent lips, nipples, and blood, silver for teeth, alloys of other colors and a variety of materials such as colored stone for representing the whites and colored iris and pupil of the eye, and dark black niello. That examples of varieties in approaches to coloration was richer than imagined has been demonstrated by Giumlia-Mair and Lehr in their investigations of black patina on ancient bronzes,7 and studies of the polychromy of Egyptian bronzes are only beginning. The protection and maintenance of ancient polished metal sculpture was dependent on a protective coating of bitumen or pine-tar pitch that both provided an overall unifying warm coloration to the surfaces and protected them from disfiguration and discoloration.8
Such a coating required maintenance in order to remain effective and records exist of payments for removing and renewing the pitch coating and repolishing the metal surface.9 Erich Pernice seems to have been the first to attempt a reconstruction of the ancient practice of applying bitumen to a polished bronze surface10 I have also applied a pitch coating to 85-5-5-5 bronze to observe the effect on the polished surface which is that of a translucent warm glaze, the color of glowing tanned skin.
It is worth noting here that protective coatings were applied not only to bronze sculpture but also on marble sculpture which was typically enhanced with painted polychromy. Vitruvius describes the wax coating used to protect the surfaces of marble sculpture.11 This coating was also removed and renewed as a maintenance practice. Pliny, the notable first century C.E. Roman author of the encyclopedic Natural History, made observations that have been frequently quoted, both about the corrosion of copper and also about the application of a protective coating on bronze sculpture.12 He uses the terms aerugo, aeruginis, to denote the “rust” (robigine) of bronze (aes), and describes various methods of producing it artificially for medical and cosmetic purposes but not for the coloration of bronze sculpture. Pliny also makes a distinction between two kinds of aerugo: one which is attractive, enhancing and stable (aerugo nobilis, or noble patina) and another which is unattractive, disfiguring and destructive, or virus aerugo which has been translated “vile” or rather “virulent”. Regarding the application of a protective coating on bronze, Pliny states that the ancients painted their statues with a coating of bitumen, and further, that it was surprising that later the Romans began gilding outdoor sculpture. The surprise seems to have been due to the fact that a polished and bitumen-coated sculpture had the appearance of gold and therefore the extra expense and effort of gilding was unnecessary. Gilding, while lavishly expensive and dangerous to the artisan gilder, would, however, have been a more durable surface treatment and require less maintenance, and a number of Roman bronzes with remains of gilding have survived, such as the Marcus Aurelius and the bronze horses of San Marco.13
Of the few documentary sources that have come down to us, an inscription of 1076 A.D. on the bronze doors of the church of S. Michele at Monte S. Angelo instructs those in charge to clean the doors once a year so that they will always be shiny and bright.14 Large-scale outdoor bronze sculpture was not being produced, but smaller scale bronzes and brasses were typically polished and occasionally inlaid with precious stones, gilded or polycrhomed with enamel. The early 9th century Mappae Clavicula describes the artificial production of corrosion products on copper using vinegar and other reagents to be used for pigments, cosmetics and various medicinal purposes but does not include coloration of bronze sculpture.15 Theophilus’ De diversis artibus16, describes a method of producing an overall, even brownish coating on bronze or copper objects by means of linseed oil and heat. However whether or not this finish was used for sculpture is not certain.
The return of large-scale bronze statuary in the Renaissance introduced a rebirth of bronze casting technology as well as a renewed interest in the artistic achievements of the ancient world. Donatello’s David, c. 1430, was the first ambitious free-standing full length bronze figure cast since antiquity. Because casting technology had not sufficiently developed , the early Florentine bronzes were typically full of casting flaws and therefore required a dark varnish that was more or less opaque. Coloristic effects could be achieved by picking out details in gilding, or as in Donatello’s St. Louis of Toulouse, on an even grander scale than the David, the piece could be cast in parts, each of which were gilded and assembled to produce a large-scale gilded bronze. The exquisite surfaces and skilled chasing with touches of parcel gilding on later bronzes, for example Verrocchio’s Christ and St. Thomas and Benvenuto Cellini’s Perseus have been revealed by conservation treatments in recent years. Both sculptures have remnants of gilded details, so the original coloration was most likely a dark or brownish resin or by application of a resin or oil with heat. Pomponius Gauricus in his De Sculptura of 1504, provides us with the first modern account of surface treatments for bronze sculpture based on his observations in the bronze foundries in Padua: “All beauty,” he says, “ appears perfect in the polishing and coloration. In the polishing we remove all harshness of the filing by means of a scraper, and we add the shine with pumice or with a point or with a burnisher. For coloration we give the color to each part whether in the cast itself (i.e. by alloying) or, he goes on to describe the following colors: “white is achieved by the application of silver leaf, yellow, i.e. gold, with gold leaf, green by wetting with salted vinegar, and black by a varnish of liquid pitch or smoke of wet straw. These colors will do for now, in waiting for the time that we will learn others.”17 I know of no existing green coloration on a Renaissance bronze, but color applied ‘to each part” appears to indicate touches of polychromy of details produced by application of gold or silver rather than an overall coloration.
The preface of Giorgio Vasari’s Vite (1550-1568) simply states that bronze, “assumes through time and by natural change a color that draws toward black…Some turn it black with oil, and others with vinegar make it green, and others with varnish give it the color of black so that everyone makes it come as he likes best.”18 The most popular and most common finish for bronze sculpture large and small seems to have been a dark lacquer that may have been the result of a misinterpretation of Pliny’s mention of a bituminous coating which was presumed to have been dark and semi-opaque rather than a translucent warm glaze. An opaque coating would serve the purpose of providing visual uniformity by concealing casting flaws and repairs. As casting technology became more sophisticated the exquisite finish and chasing of late 16th century works, for example, by Giambologna and the Susini workshop, translucent reddish lacquers of exquisite beauty were employed producing the prized effect of polished metal viewed through a dark, red-brown, glossy varnish. For works on a larger scale either a dark varnish or simple heating over a smoky straw fire and rubbing with oil served to produce a uniform lustrous and translucent brown of copper oxide.
The account by André Felibien in his Principes of 1699 provides the only account for patination in the 17th century that I have been able to locate: “After [the bronzes] have been well cleaned and repaired, one gives them if one wishes, a color. There are those who use for that purpose oil and sanguine (red earth pigment), others make it become green with vinegar. But with time bronze takes on a varnish which tends toward black.”19
Perhaps the most surprising discovery in my initial exploration of the history of the coloration of bronze sculpture, was that the word patina was first used not in reference to the coloration of bronze but in reference to the effects of age and discolored varnish on paintings and only towards the middle of the 18th century came to be applied to corrosion crusts found on antique bronze sculpture and artifacts. The first printed definition of the word is in a variant form, patena, that can be found in Filippo Baldinucci’s Vocabolario Toscano dell’ Arte del Disegno published in Florence in 1681. Baldinucci defines patena as follows: “…a term used by painters, called by others a skin (pelle), namely that general, dark tone which time causes to appear on paintings, that can occasionally be flattering to them.”20 Patena is an old Italian word used to refer to a shiny dark varnish applied to shoes,21 and whose meaning was easily understood as a description of the darkened varnish on painting.
It was not until the mid-18th century that the word appears in a dictionary where it refers to green corrosion products found on bronze artifacts. Patine is defined in the French Encyclopedie of 1751 as follows: “There is no French word to express that beautiful and brilliant color of verdigris that copper does not always assume; the attractiveness of this color to the eye and the difficulty in describing it (because all coppers do not uniformly develop it) is highly valued by the Italians who call it patina as one dares to do here after their example and by the example of M. le Comte de Caylus who states correctly that one should be allowed to adopt a foreign word at least in the language of the arts of which this Encyclopedia is the Dictionary”.”22
The Encyclopédie also provides information about artificial patination under the entry on sculpture: “ As to the pitch with which the ancients covered their bronzes, we have no desire for it; the smoke and preparations of our artists are far preferable, because they have less thickness.”23
The philological aspects of the word appear to reflect the historical situation: while coloristic effects were achieved in bronze sculpture by a variety of means from earliest times, it was not until the 18th century and the new enthusiasm for archeological bronzes that green corrosion products began to be appreciated and valued in themselves. According to the Oxford English Dictionary, the earliest recorded English usage of patina describing green corrosion products on bronze as late as 1797. According to the Italian etymological dictionaries, the Italian verbs meaning to give a patina, patinated, and patinator are all 19th century in origin.24 It was not until the late 19th century that artificial patination of bronzes by chemical means, with or without heat, was generally and widely practiced.
It is hard for us living in the 20th century to imagine many aspects of life in the pre-industrial world. No one living today can remember a time before the invisible invasion of sulfur-polluted air produced the slow and subtle changes in the appearance of outdoor urban bronzes from brown lustrous oxide or dark lacquer to a general overall opaque, matte, black or pale green. It is not surprising, then, that in most cities, where most outdoor bronzes have been placed, and where sulfur pollution has been the greatest, that a green appearance came to be accepted as the expected norm, and was described as “natural patina” and desirable when in fact it was the result of un-natural causes. Further, since “natural” was equated with “good” and “desirable” no one thought to look closely at the surfaces of these monuments to discover the truth that their surfaces were being progressively destroyed physically and irretrievably and their artistic and visual message was being altered and distorted. Throughout my conservation training that began in the late 1950’s, outdoor sculpture was never mentioned as a conservation problem. It became a great irony that the most highly visible, and in many cases, the most sizeable works of art were being destroyed and the damage was only recognized after it was too late. It was only in the early 1970’s when the gilded ancient bronze horses on the façade of the basilica of San Marco were studied closely that the conservation world began to be awakened to the vulnerability of bronzes exposed to the polluted atmosphere of the modern world, and to face the complex problems of treatment for works of art already irreparably damaged.
At the ICOM-CC meetings in Madrid in 1972 the first presentations were made revealing the severity of corrosive attack on outdoor bronze sculpture. Joseph Riederer’s detailed photographs of the surfaces of outdoor bronze sculpture in Munich encouraged observations in other parts of the world where similar serious corrosion was observed and a previously ignored conservation problem began to be recognized. The conservation community first turned to conservators of archaeological metals who could identify corrosion products, typically called “patina”, who could, like John Gettens, distinguish between what was termed “noble” and “vile” patina, and could execute appropriate and ethical treatments. However applying these criteria to outdoor bronze sculpture was problematic: The corrosion products on outdoor bronzes were altogether different from those that had been produced under burial conditions, basic copper carbonates in the form of azurite and malachite predominating in the former with instances of copper chlorides representing vile patina; and brochantite or basic copper sulfate predominating on the latter. The presumption that the green brochantite patina on outdoor bronzes, widely promulgated in the literature of corrosion science as not only protective but attractive and “natural”, was proven false.
The expanding demand for outdoor bronze sculpture in the 19th century was met by developing technology particularly in Germany where the emergence of industry and science combined to make large scale production of sculpture possible and also the industrial development that introduced large quantities of sulfur into the atmosphere as well as the scientific development in chemistry which enabled scientists to detect the cause of changes in the appearance of outdoor bronzes in Berlin in the 1860’s.
The Royal Foundry in Munich directed by Ferdinand von Miller was the pre-eminent foundry in Europe for bronze sculpture on a large scale from the 1830’s up until the 1880’s having produced the colossal 18 meter high cast of Schwanthaler’s Bavaria between 1837-48. Von Miller used a sand casting technique producing bronze casts of extremely high quality and with an alloy in which he took particular pride. Von Miller used an alloy intentionally selected to give “luster and malleability” and “to prevent the statues from turning green by years of exposure.” Von Miller’s letters preserved in the Valentine Museum in Richmond, Virginia, provide specific instructions for maintenance of the Washington Monument bronzes cast in Munich between 1849-69, as well as his stated desire regarding the appearance of the bronzes. Maintenance was important, “for the color of the metal imparts a peculiar beauty to works of art.” The fame of von Miller’s “gold bronze” was widespread by the 1870’s, according to an article in the New York Tribune in 1874, in which it was compared with the predominantly brown tones of contemporary bronzes from other foundries.25
The Munich foundry of von Miller was overtaken by the exceptional development of French foundries in the 1880’s to meet the enormous new demand for outdoor monuments, and the re-discovery of lost wax casting to meet this demand. Cire perdue casting, which has dominated fine arts casting ever since, presents numerous artistic advantages for sculptors. Editions of a work can be produced with relative ease, and surfaces and textures, even with detailed undercuts can be reproduced with exceptional precision and with minimal need for chasing and mechanical reworking. Along with the expansive development of lost wax casting in France in the latter part of the 19th century to meet the increasing demand for outdoor bronze monuments came the development of artificial chemical patination as a specialized art. The master patineurs took over the coloration of bronzes in the foundry and those, such as the Limet brothers, not only acquired great fame in their own right in producing patinas but also served as consultants on coloration for artists such as Rodin. Artists themselves became increasingly interested in the possibilities of coloration and the more aware were also disturbed by the effects that they came to observe on deteriorating surfaces of sculpture exposed to polluted urban air.
Augustus Saint-Gaudens, the American sculptor who studied in Paris in the latter part of the 19th century and was intensely preoccupied with the patination and finishing of his bronzes, had his large equestrian monument of General Sherman gilded at his own expense because he feared that his sculptures woud end up “looking like old stove pipes.”26
The earliest descriptions of undesirable changes in the appearance of outdoor bronze sculpture, as well as documentation of scientific research into the cause for the changes were provided by Magnus in the 1860’s and the reports of the activity of the Berlin Patina Commission.27 This work, continued by Puscher,28 Donath29 and Vanino and Seitter30, and Hiorns, whose important study appeared in 1892 in London31 began the development of the patina literature with “patina” being equated with corrosion products on bronze sculpture, and making the careful distinction between patina that is “natural” and patina that is “artificial” as well as, following Pliny’s distinction, patina that is “noble” or “vile”. Causes for undesirable change in appearance on outdoor sculpture were recognized as resulting from gaseous sulfur compounds released by industrial activity and methods of producing a controlled and desirable variety of colored patinas on bronze surfaces was explored.32 The rich information contained in these early studies have been largely ignored in the later literature and the alarm sounded for the need to protect outdoor bronze sculpture in urban environments went unheeded and then forgotten with the intervening historical events of two World Wars.
Some of the most interesting passages from these early writers are to be found in passages describing what they consider to be desirable aspects of a “noble” patina whether “natural” or “artificial”. Hiorns admires what he describes as the effects of “Nature” on metals, and states that it is desirable to attempt to imitate those effects in producing an artificial patina with the important condition: “…always provided that the colours aimed at are strictly in keeping with the metallic character.”33 Elsewhere he states, “a metallic article is not like a canvas or paper, which has to be completely covered with paint of all colours…but a material which must always assert its peculiar metallic character, so that there is never any doubt as to its real nature.”34 The question of distinguishing “noble” from “vile” appears in the earliest bronze conservation literature published by Friedrich Rathgen, founder of the first museum scientific laboratory in Berlin in the 1890’s concerned primarily with archeological bronzes.35 This theme is again taken up by Gettens in a paper, “Patina Noble and Vile” presented to the symposium, “Art and Technology”, sponsored jointly by Harvard University and M.I.T. in connection with a major exhibition of ancient bronze artifacts.36
It should be obvious that the distinctions “natural” and “artificial” and “noble” and “vile” or “virulent” become particularly important where conservation is concerned and these categories are different for archeological bronzes and for outdoor bronze sculpture. Where they have come to be fairly well defined for archaeological metals they are still problematic for bronze sculpture which presents a host of very different considerations not all of which can be solved with the precision of scientific inquiry and clear-cut results. Many outdoor bronzes have been treated since the early 1970’s including the most important bronzes in Western art and all of these treatments have had to struggle with the complexities of large scale, future maintenance, effectiveness and durability outdoors, surface treatment, and aesthetic appearance. Further, nearly all of them result in a change of appearance requiring justification from an ethical and aesthetic point of view. Such changes have resulted in bitter disputes, among the earliest of which was described in a book published in 1888 entitled, Der Patinakrieg: der Restaurirung des Maxdenkmals zu Innsbruck und der Streit für und wider dieselbe,37 “The Patina War: the Restoration of the Maximillian monument in Innsbruck and the struggle for and against it”.
Patina on outdoor bronzes has in every case required intelligent and ethical consideration involving consideration of wide and diverse aspects of knowledge both scientific and humanistic. Unlike discolored varnish on a painting, it is formed from the substance of the metal itself and its presence represents loss of original surface. The identification of patina on outdoor copper and copper alloys by Vernon and Whitby in 1929 from studies on copper roofs38 made the clear distinction between patinas formed in the open air identified as primarily basic copper sulfate, brochantite, and the patinas formed under burial conditions which were primarily the copper carbonates, malachite and azurite. The conclusions of Vernon and Whitby, though impressive from the scientific point of view were tragically misleading insofar as bronze sculpture was concerned. Their statement that the green patina that formed on outdoor bronzes was “natural”, “protective” and “aesthetically pleasing” contributed to what could be described as a “blind spot” where outdoor bronzes were ignored insofar as conservation was concerned.
Studies on the San Marco Horses in Venice followed by the investigations of Riederer39 and Lehman40 reported on at the 1972 meetings of the ICOM-CC meetings are landmark investigations demonstrating that patinas, now called “corrosion damage” and “corrosion” to emphasize that they are not benign, could not be described as “natural”—they are formed by man-made pollution—nor “protective” –they promote rather than retard surface deterioration—nor could they be in any way be described as “aesthetically pleasing”—as they form randomly colored, speckled and streaked surfaces that serve as camouflage to the sculptural forms. The work of Weil, et. al., further strengthened and elaborated these conclusions.41
Two recent studies demonstrate interesting approaches to the study of patina presented at a conference held at the Tate Gallery in September of 1995. Binnie, describes a technique of color monitoring on outdoor bronze sculpture in Ottawa42, and Summers presents the problems of patina in two identical bronzes by Henry Moore.43
Phoebe Dent Weil
Northern Light Studio, LLC
1602 Locust Street / Suite 815
St. Louis, MO 63103
Fax: +1 314-588-9681
1. For a discussion of specific problems of the evolving notions of the relationship of color and form see Weil, P., Patina: Historical Perspective on Artistic Intent and Subsequent Effects of Time, Nature, and Man, in Naudé, V., (ed.), Sculptural Monuments in an Outdoor Environment, Philadelphia, PENNSYLVANIA ACADEMY OF THE FINE ARTS, 1985, pp. 21-22.
2. I have discussed patina, the history of the meaning and use of the word, its evolving aesthetic perspective and the practice of artificial patination in two previous articles, the first: Weil, P.,“A Review of the History and Practice of Patination”, in Brown, B., Burnett, H. et.al. (eds), Corrosion and Metal Artifacts, National Bureau of Standards Special Publication 479, Washington, DC: US GOVERNMENT PRINTING OFFICE, 1977, pp. 77-92, reprinted in Price, N., Talley, M. , and Vaccaro, A., (eds.), Historical and Philosophical Issues in the Conservation of Cultural Heritage, Los Angeles THE GETTY CONSERVATION INSTITUTE, 1995, pp. 394-414. NOTE: the following errata in the Getty reprint: p. 394: should read “virus aerugo”; and on p. 404, bottom of the page, should read “largely” instead of “little”. The second article is Weil, P., Patina: Historical Perspective on Artistic Intent and Subsequent Effects of time, Nature and Man, in Naudé, V., (ed.), Sculptural Monuments in an Outdoor Environment, Philadelphia, PENNSYLVANIA ACADEMY OF THE FINE ARTS, 1985, pp. 21-27.
3. See, e.g., Smith, C.S., A History of Metallography, 2nd ed., Chicago, 1965, p. 2; Partington, J.R., Origins and Development of applied Chemistry, London, 1935; Hopkins, A.J., Alchemy, Child of Greek Philosophy, N.Y., 1934.
4. Smith, C., Materials and the Development of Civilization and Science, in Science, 148, April-June 1965, p. 908.
5. Forbes, E., The Origins of Alchemy, in Studies in Ancient Technology I, 2nd ed., Leiden, 1964.
6. Weil, P. (1977), pp. 81-83; Weil, P., (1985) pp. 24-25. Further, see the following articles in La Niece, S., and Craddock, P. (eds), Metal Plating and Patination: cultural and Historical Developments, Oxford, BUTTERWORTH-HEINEMANN, LTD., 1993: Hughes, R., Artificial Patination, p. 6; Born, H., Multi-Colored Antique Bronze Statues, p. 19; Craddock, P. and Giumlia-Mair, A., Beauty if Skin Deep: Evidence of the Original Appearance of Classical Statuary, p. 30; as well as Mattusch, C., Classical Bronzes, Ithaca and London, CORNELL UNIVERSITY PRESS, 1996, pp. 24, 26, 29; Mattusch, C., Greek Bronze Statuary, Ithaca and London, CORNELL UNIVERSITY PRESS, 1988, pp. 98.ff.
7. Giumlia-Mair, A. and Lehr, M., Patinating Black Bronzes: Texts and Tests, in Proceedings of the Fourth International Conference on the Beginning of the Use on Metals and Alloys (BUMA-IV), May 25-27, 1998, Kunibiki Messe, Matsue, Shimane, Japan, The Japan Institute of Metals.
8. Weil, P., (1977), p. 82; Weil, P., (1985), p.25. Further see the discussions regarding the black coating on the Riace bronzes in Born, H., op. cit. p.24.; Craddock, P. and Giumlia-Mair, A., op. cit., p. 30.; Scott, D., Copper and Bronze in Art, Los Angeles, GETTY PUBLICATIONS, 2002, pp. 328-329.
9. Pernice, E., Untersuchungen zur antiken Toreutik, V. Natürliche und Künstliche Patina im Altertum, in Jahreshefte des Osterreichischen Archäologischen Institutes in Wien, XIII, 1910, pp. 102-107.
10. Pernice, E., op. cit.
11. Vitruvius, On Architecture, 2 vols., Granger, F. (ed), Loeb Library, Cambridge, MA, HARVARD UNIVERSITY PRESS, 1970, vol. II, p. 119 (VII.ix. 3); Reuterswärd, Studien zur Polychromie der Plastik Griechenland und Rom, Stockholm, 1960; Cagiano de Azevedo, M., Conservazione e restauro presso I Greci e I Romani, Bollettino dell’ Istituto Centrale del Restauro, 9-10, 1952, pp.53-60.
12. Pliny, Natural History, 10 vols, Loeb Library, vol. IX, Rackham, H. tr., London, 1968, XXXIV.
13. Weil, P. (1977), pp. 82-83.
14. Federici, V. Le Porte Bizantine di San Marco, Venice, STADIUM CATTOLICO VENEZIANO, 1969.
15. Smith, C. and Hawthorne, J., Mappae Clavicula: A Little Key to Medieval Techniques, Philadelphia, 1974.
16. Theophilus, De diversis artibus, (1110-40) London, Dodwell, C.R., ed., THOMAS NELSON, 1961.
17. Pomponius Gauricus, De Sculptura, 1504, p. 239.
18. Vasari, G. Le Vite…, 1550, 1568, Milanesi, G., ed., Florence 1878; “Prefix” to the Vite, tr. And ed. Maclehose and Brown, Vasari on Technique, N.Y., 1960, pp. 165-166.; Bettarini, R. and Barocchi, P., eds, Verona, 1966, vol. I, p. 103. The quote reads:
“Questo bronzo piglia col tempo per se medesimo un colore che trae in nero e non in rosso come quando si lavora. Alcuni con olio lo fanno venire nero, altri con l’aceto lo fanno verde, et altri con la vernice li dànno il colore di nero, tale che ognuno lo conduce come più gli piace. Nel che si vede questa arte essere in maggior eccellenza che non era al tempo degli antichi.”
19. Félibien, A., Des Principes de l’Architecture, de la Sculpture, de la Peinture, et des autres Arts qui en dependent, Paris, 1699, Farnborough, Hants., England, 1966, p.239.
“Après qu’elles sont bien nettoyées & reparées, on leur donne si l’on veut une couleur. Il y en a qui prennent pour cela de l’Huile & de la Sanguine; d’autres les font devenir vertes avec du Vinaigre. Mais avec le temps la bronze prend un vernis qui tire sur le noir”
20. Baldinucci, F., Vocabolario Toscano dell’Arte del Disegno, Florence, 1681. “
”Patena, voce usata da’ Pittori, e diconla altrimenti Pelle, ed è quella universale scurit~a che il tempo fa apparire sopra le pitture, che anche talvolta le favorisce.”
21. Battisti and Alessio, Dizionario Etimologico Italiano, Florence, 1954. (patina)
The Cambridge Italian Dictionary, vol. I, Reynolds, B. (ed.) , Cambridge, 1962. (patina)
22. Diderot and d’Alembert, Encyclopédie ou dictionnaire raisonnedes sciences, des arts et des métiers, par une societe de gens de letters, Neufchastel, 1765; Lausanne, 1780-82.
“Patine: Il n’y a point de mot francois pour exprimer cette belle & brilliante couleur de vert-de-gris que le cuivre ne prend pas toujours; l’agrément de cette couleur pour l’oeil & la difficulté de la renconter (car tous les cuivres ne s’en chargent pas également), la rendent trés-recommandable aux Italiens, qui la nomment patina , comme on ose ici le faire d’après eux, & par l’example de M. le comte de Caylus, Il doit etre permis, dit-il avec raison, d’adopter un mot étranger au moins dans la langue des arts,”
23. Diderot, Encyclopédie, op. cit., “Quant à la poix dont les anciens couvroient leurs bronzes, nous n’avons rien à desirer; les fumes & les preparations de nos artistes sont d’autant préferables, qu’elles ont moins d’épaisseur.”
24. Battisti and Alessio, op. cit.
25. Cook, C., Palmer’s Statue of Livingstone in New York Tribune, July 8, 1874, pp. 4-5.
26. Dryfhout, J., Augustus Saint-Gaudens, in Wasserman, J., (ed.) Metamorphoses in Nineteenth-Century Sculpture, Cambridge, MA, HARVARD UNIVERSITY PRESS, 1975, p. 183.
27. Magnus, G., Uber die Einfluss der Bronzezusammensetzung auf die Erzeugung der schönen grunen Patina, in Dinglers Polytechnisches Journal, 172,1864, pp. 370-376. Further, see articles listed in the bibliography published by S. Lewin and S. Alexander, The Composition and Structure of Natural Patinas, Part I, Copper and Copper Alloys, Section A, Antiquity to 1929; Section “B, 1930 to 1967, Art and Archaeology Technical Abstracts, VI, 4, 1967; and VII, 1, 1968. Also references in P. Weil (1977), p. 91, note 51.
28. Puscher, C. Artificial patinas, in Polytechnisches Notizblatt, 38,90, 1883.
29. Donath, E., Artificial patination, in Dinglers Polytechnisches Journal, 253, 376-80, 1884.
30. Vanino, L, and Seitter, E., Patina. Its Natural and Artificial Formation on Copper and its Alloys, Vienna, 1903.
31. Hiorns, A., Metal-Colouring and Bronzing, 2nd ed., London, 1911.
32. The rich literature on artificial patination has been outlined in Weil, P. (1977), pp. 91-92, Recent contributions include Hughes, R., and Rowe, M., The Coloring, Bronzing and Patination of Metals: A Manual for the Fine Metal Worker and Sculptor, London CRAFTS COUNCIL, 1982; and Hughes, R., Artificial Patination in La Niece, S., and Craddock, P., Metal Plating and Patination, Oxford, BUTTERWORTH-HEINEMAN, 1993, pp. 1-18
33. Hiorns, A., op. cit., p. 5.
34. Hiorns, A., op. cit., p. 67.
35. Rathgen, F., The Preservation of Antiquities, Cambridge, 1905, pp. 34-36.
36. Gettens, J., Patina Noble and Vile, in Doeringer, S., Mitten, D., Steinberg, A., Art and Technology, Cambridge, MIT PRESS, 1970, pp. 57-68.
37.Der Patinakrieg: die Restaurirung des Maxdenkmals zu Innsbruck und der Streit für und wider dieselbe, Innsbruck, Wagnerschen Universitaets-Buchhandlung, 1883.
38. Vernon, W, and Whitby, L., The Open-Air Corrosion of Copper: A Chemical Study of the Surface Patina, in Journal of the Institute of Metals, 42 (1929), pp. 181-95 (Part I) 44 (1930) p. 389-96 (part II; 49 (1932)153-61 (Part III).
39. Riederer, J., Corrosion Damage on Bronze Sculptures, preprint of paper presented to ICOM Committee for Conservation, Madrid, October 1972,
40. Lehmann, J., Corrosion of Monuments and Antiquities made of Copper and Copper Alloy in Outdoor Exhibits, preprint of paper presented to ICOM Committee for Conservation, Madrid, October 1972.
41. Weil, P., et.al., The Corrosive Deterioration of Outdoor Bronze Sculpture, in Preprints of the Contributions to the Washington Congress, 3-9 September 1982: Science and Technology in the Service of Conservation, London, INTERNATIONAL INSTITUTE FOR CONSERVATION, 1982, pp.130-34.
42. Binnie, N., Colour Monitoring on Outdoor Bronze Statues in Ottawa, Canada, in Heuman, J., (ed.), Marble to Chocolate: the Conservation of Modern Sculpture, Tate Gallery Conference 18-20 September, 1995, London, ARCHETYPE, 1995, pp. 73-81.
43. Summers, Jl, Gilding the Lily: the Patination of Henry Moore’s Bronze Sculpture, in Heuman, J., (ed.), op. cit., pp. 144-151.