Aluminum Finishes in Postwar Architecture Thomas C. Jester Understanding the evolution and range of aluminum finishes is critical to making treatment decisions. Fig. 1. Himco Storefront Construction, cover and rolled mouldings, published by Himmel Brothers, 1946. Courtesy of the APT Building Technology Heritage Library. If and when colored aluminum becomes a permanent thing, I think it opens up a great many fields simply because the materials we have on hand really do not give us the palette we need to cover today’s needs. —Minoru Yamasaki, Aluminum in Modern Architecture, 1958 The twentieth century witnessed an explosion of new materials and assemblies for construction. Avant-garde architects who subscribed to the tenets of Modernism embraced reinforced concrete and glass to create remarkable new buildings. If concrete and glass were the first two critical material legs of the stool for Modern architecture, metals were the important third leg. The material qualities of building facades, in particular, relied heavily on metals as the relationship ­between structure and skin evolved in the period after World War II.1­ 41 APT BULLETIN JOURNAL OF PRESERVATION TECHNOLOGY / 46:1 2015 Industrial materials and assemblies with a wide array of finishes and standard, known properties became the designer’s palette.2 Architects in the Modern era selected metals with finishes that produced a wide range of patterns, textures, and colors. Metals were selected not only because they met specific performance criteria and characteristics but also because they conveyed newness, celebrated industrialization, and even highlighted their specific qualities for poetic effect.3 The development to Modern architecture was made possible, in part, through the substitution of lightweight for heavy materials, and the use of metals was one of the keys that made the changes possible.4 In 1947 the frontispiece to the Architectural Metal Handbook, published by the National Association of Ornamental Metal Manufacturers, declared, “Freedom of expression is the cornerstone of progress in architecture. The metals of old, supplemented by the alloys of today, provide the strength, utility and permanence, dignity and beauty to make possible that freedom.”5 This statement signaled acceptance of the growing impact of aluminum alloys in the building industry by Modern architects in place of more traditional metals, such as bronzes and nickel silver, which had been used widely through the 1930s.6 Other modern metals, like Monel, were more expensive and used more commonly for applications like roofing.7 Lightweight metals saved time, space, and weight. Architect Eero Saarinen observed that “from the miraculous potentials of engineering and science will come new materials, new possibilities and new problems. These will have to be absorbed.”8 This was particularly true for aluminum. Throughout the late 1920s and 1930s, architects used a variety of white “silvery” alloys, including aluminum, stainless steel, nickel silver, Benedict metal, zinc, and Monel, for decorative elements in buildings.9 A wide range of colors and textures could be achieved with minor adjustments to the composition of the metals and mechanical manipulation of the metal surface with buffing, brushing, and blasting.10 42 Fig. 2. Alcoa Aluminum Handbook, published by the Aluminum Company of America, 1957. This manual featured Alcoa’s available alloys that met commercial standards and designations set by the Aluminum Association. William Van Alen, the architect of the Chrysler Building in Manhattan, was an early adopter of stainless steel. He prized the permanence of the bright finish, which he felt was important to accentuate the lines of the building and achieve a finish that constantly changed in various light conditions.11 Doors, door hardware, letter boxes, divider strips in terrazzo, and grilles were among the many uses of white metals during the 1930s to achieve decorative effects on the interiors and exteriors of buildings. Aluminum could be cast, forged, and extruded to create countless types of architectural elements. Aluminum’s ascendency was swift, as the material became more affordable. By the late 1930s the Aluminum Company of American (Alcoa) was producing residential and commercial aluminum windows, which began competing with wood and steel windows and rapidly eclipsed them. Alcoa’s 1938 product literature stated, “Natural aluminum is striking in appearance yet neutral in effect.”12 Storefront construction also witnessed significant changes as a result of advances in metals. In 1906 Francis Plym obtained a patent for a metal storefront and soon after founded the Kawneer Company in Kansas City, Missouri. Early storefront systems made with solid copper gave way to aluminum, and by 1937 it was estimated that 75 percent of Kawneer’s product line was aluminum.13 The Himmel Brothers Company’s 1946 catalog, entitled Himco Storefront Construction, included “Modern Metals for Glass Settings,” which featured “Bronze and Alumilited Aluminum” in extruded shapes and “Stainless Non-Magnetic Steel 188, Bronze, Alumilited (anodized) Aluminum, and Stainless Laminated Metal (Pat.)” in cold-rolled products (Fig. 1).14 Aluminum’s hegemony would continue to the point that Kawneer’s 1960 storefront catalog included only aluminum products with the following finish specification: “All exposed portions of aluminum storefront moldings shall be buffed to a mirror-like finish…and shall be given an anodic oxide treatment in accordance with Alcoa Specification ‘Alumilite 204 A1 R1.’”15 The rapid proliferation of aluminum building products accelerated in the postwar period, partly due to cost but also because of the shift to the growing number of alloys marketed annually (Fig. 2). By 1954 manufacturers adopted standard designations created by the Aluminum Association for the voluminous number of wrought alloys.16 The new Aluminum Association designations permitted new alloys to be assigned a unique designation once accepted as a standardized metal with known properties. Experimentation and Postwar Expansion Architects frequently experimented with metal materials. One of the most striking early examples of aluminum used for a Modernist design was the Aluminaire House, designed by Lawrence Kocher and Albert Frey. Constructed in 1931 for the Allied Arts and Building Products Exposition in New York City, ALUMINUM FINISHES IN POSTWAR ARCHITECTURE the building was partially subsidized by Alcoa, which provided the aluminum components, including the corrugated panels. At the Century of Progress International Exposition in Chicago in 1933, two houses looked to the future with metals. The House of Tomorrow featured metal siding, and the ArmcoFerro House was clad with 13-inchwide porcelain-enamel panels attached with battens. During World War II, Vultee Aircraft hired Henry Dreyfuss and Edward Larrabee Barnes to design prefabricated metal housing using 18-foot-long-by-8-foot-tall aluminum sheets bonded to a cellular core, but the prototypes were never mass produced.17 Buckminster Fuller’s Dymaxion House was noteworthy for its experimentation with lightweight aluminum alloys that had high strength-to-weight ratios.18 Although the projected mass production never occurred, Fuller’s prototypes — designed between 1941 and 1946 and built in 1947 — reflected the passion of its innovative designer. Following World War II, the largest aluminum producers — Alcoa, Reynolds, and Kaiser — pursued new markets to absorb their increased wartime-production capacity, and the building industry was targeted with aggressive marketing through publications, demonstration houses, and award programs.19 The widespread availability of aluminum in the late 1940s and early 1950s also coincided with the rapid arrival of another important building assembly: the curtain wall. Pietro Belluschi’s Equitable Savings and Loan Building in Portland, Oregon, constructed in 1948, featured prefabricated cast- and sheet-aluminum panels in a contrasting configuration to emphasize the reinforced-concrete structure.20 In 1949 French architect Jean Prouvé, a staunch supporter of industrial construction methods and new materials, incorporated large, prefabricated aluminum panels to form the curtain wall for the Building Trades Federation headquarters in Paris.21 On a larger scale, the 30-story Alcoa Building in Pittsburgh, Pennsylvania, designed by Harrison and Abramovitz and completed in 1953, was widely publicized as a “daring expression of the metal curtain wall.”22 In contrast to the mostly-glass curtain wall of the early 1950s, the Alcoa Building’s curtain wall, a so-called “Aluminum Dress,” was formed with large 6-footby-12-foot stamped anodized panels of “iridescent gray color” (Fig. 3).23 Aluminum windows with rubber gaskets pivoted to allow cleaning from within the building. Alcoa’s promotional materials pointed out that “if the Alcoa Building had used conventional construction, it would have weighed in at an additional 10,340 tons!”24 In the late 1950s aluminum curtain walls increasingly featured stamped “machine ornament,” a prominent example of which was 666 Fifth Avenue in New York City, which at the time of completion in 1957 was Fig. 3. Alcoa Building, curtain-wall detail, Aluminum on the Skyline, published by the Aluminum Company of America, c. 1954. the largest aluminum curtain wall ever built (Fig. 4).25 Later, more expressive uses of aluminum as “skin” to deemphasize the structural frame would be found in works like Cesar Pelli’s 1968 design (while at Daniel, Mann, Johnson, Medenhall) of the Comsat Laboratory Building in Clarksburg, Maryland (Fig. 5). Joint widths were minimized to allow the clear anodized aluminum to ­appear as a wrapper, conveying a tautness and lightness to the structure.26 43 APT BULLETIN JOURNAL OF PRESERVATION TECHNOLOGY / 46:1 2015 tion would grow rapidly in the postwar period, particularly for curtain-wall assemblies.29 The curtain-wall assembly for General Motors Technical Center in Warren, Michigan, designed by Eero Saarinen in 1950, was a 2-inch-thick composite panel of porcelain enamel on aluminum, laminated to a paper honeycomb core.30 Other core materials used for honeycomb composite panels in the postwar period included aluminum, stainless steel, fiberboard, and plasticimpregnated glass.31 Fig. 4. Tishman Building, 666 Fifth Avenue, New York, New York, 1957, designed by Carson and Lundin. Detail of aluminum and porcelain enamel curtain wall. Photograph by the author. Fig. 5. Comsat Building, Gaithersburg, Maryland, 1968. Photograph by the author, 2015. Metals also were often used in the growing number of composite materials that took advantage of the properties of more than one material to make lighter, stronger materials. In 1947 Steel magazine would declare that “composite material is the Janus of many of today’s cleverly engineered lighter structures.”27 One of the early composite materials using metal was the Haskelite Manufacturing Company’s Plymetyl. Light-gauge metals — zinc-coated steel, aluminum, Monel, stainless steel, and porcelain enamel — were bonded with phenolic resin to plywood or insulating board.28 Composite sandwich construc44 In 1940 Buffalo-based Rigidized Metal Company introduced deep-textured sheet metals for architectural applications in both ferrous and non-ferrous metals, including aluminum. Formed by rolling, the embossed Rigid-Tex sheets came in a wide range of patterns and varying pattern depths (Fig. 6). Promoted for its increased tensile strength and elimination of any distorted surface reflections (oil canning), the products gained widespread acceptance in exterior and interior uses, ranging from curtain-wall panels to elevator cabs.32 The growing popularity of textured aluminum during the 1950s spawned competitors. The Aluminum Company of Canada (Alcan), for example, offered embossed aluminum sheets and coil in a variety of gauges and patterns. Alcan’s 1956 promotional catalog noted that its sheet could be painted or lacquered, in addition to the natural finish it offered.33 Postwar Aluminum Uses and Finishes Stainless steel and aluminum dominated as the metals of choice for architects during and after World War II and into the early 1950s. As the number of finishes for stainless steel and aluminum grew, they provided architects with more choices than ever before. For Mies van der Rohe, materials were to be used for structure or enclosure, and he believed materials should be used based on research and facts. He commented in 1956 that “the danger with aluminum is that you can do with it what you like; that it has no real limitations.”34 But Mies’ warnings would not stop the major three aluminum producers from flooding the market with an ever-growing array of aluminum components, including windows, doors, siding, roofing, storefronts, curtain walls, sun-control devices, flashing, railings, copings, and acoustical ceiling assemblies, not to mention structural components. Aluminum quickly became ubiquitous in buildings, partly because it had become economical but also because of the aluminum industry’s marketing prowess. Types of Aluminum Finish Finishes for aluminum fall into three categories: mechanical, inorganic, and organic.35 Typical mechanical finishes, achieved with brushes or abrasives to impart texture and contrast, ranged from satin, sandburnished, polished, sandblasted, and spin finished to frosted. Inorganic finishes on aluminum could be created with chemicals, chemical oxidation, electrochemical treatment (anodizing), electroplating (metal fused to aluminum), and porcelain enamel (glass fused to aluminum).36 Organic finishes include synthetic lacquers, alkyd methacrylate lacquers, and paint. Anodizing, prized for its corrosion resistance and ability to maintain its original appearance over time, would prove to be the most important aluminum finish. Anodizing was first used on British Duraluminum for sea-plane parts in 1923 based on the patented Bengough-Stuart process. A process using sulfuric acid was patented by Gower and O’Brien in 1927, and the Japanese introduced an anodizing process with oxalic acid in 1923 that was widely used for architectural applications in Germany.37 Alcoa first patented its color-anodizing process in 1923 and by 1928 was commercially producing anodized aluminum under its Alumilite trade name.38 Advances in processes and techniques for anodizing aluminum played an important part in its widespread use in buildings. The anodizing process created a thin, protective film of aluminum oxide that could be clear or colored. According to the Reynolds Metal Company, The result is a uniform, hard glass-like film that is not on top of the metal but an integral part of the metal surface itself. Its thickness will be ALUMINUM FINISHES IN POSTWAR ARCHITECTURE from 0.0008 to 0.0010-inch, according to the processing. Its appearance will vary from that of a clear, perfectly transparent coating, to a dark, opaque, slate gray….This film not only offers great resistance to abrasion and corrosion but also provides amazingly effective protection against weathering.39 In 1938 Alcoa noted in its product literature that its Alumilite finish was “proving useful for architectural parts such as storefronts which must resist atmospheric attack for prolonged periods, and still present a pleasing white appearance.”40 Architectural applications in the immediate postwar period typically used Alumilite No. 204 for wrought products and Alumilite No. 704 for castings.41 Reflecting the fact that anodized aluminum remained somewhat of a novelty well into the 1950s, the Reynolds Metal Company devoted an entire section of its 1958 supplement to Aluminum in Modern Architecture to the benefits of anodizing. It declared: Not only did aluminum offer the benefit of its strength-to-weight ratio: it had other possibilities that would interest architects, including color.42 Postwar Metals and Color The prolific use of white metals in the 1930s gave way to the growing use of stainless steel and aluminum in the 1940s by architects as Modernism took hold in the United States. Color was often associated with ornament, and the immediate postwar period relied largely on a palette of materials with “natural” color (in contrast to those deemed artificial). High-style Modernists favored “a somewhat elastic range of materials: travertine, marble, wood, leather, glass, steel, and aluminum, each in their variety of finishes.”43 Louis Kahn’s use of mill-finished stainless steel on the Yale Center for British Art in New Haven, Connecticut, in 1969 was one example of a muted visual effect that embraced the natural characteristics of a metal finish (Fig. 7). Kahn’s deep interest in the character and nature of materials led him to the “pewter-colored” patina on the British Center’s metal cladding. Kahn described his vision for the appearance by stating, “On a cloudy day it would look like a moth, on a sunny it would look like butterfly.44 Interest in color grew as Modern architecture morphed away from the perceived monotony of the glass-andmetal boxes of the immediate postwar period and as Modernism became more mainstreamed for the masses. Taking into account the inherently disruptive and transformative nature of scientific advances that led to new materials, manufacturers sought to expand their reach in the architectural market by offering new metal products with a variety of textures, patterns, and colors. Architect Victor Gruen argued in 1958 that “if applied with judgment, taste, and imagination, colored aluminum opens tremendous new possibilities in liberating our urban environment from the dreariness created by the exclusive use of the somber, ‘safe’ colors,’” which he considered to be black, white, and gray.45 Throughout the 1950s interest in color expanded, and manufacturers responded to give architects more choices when designing with metals. In 1957 Alcoa’s newly created Residential Building Products Division hired Modernist architect Charles Goodman to design its “Care-Free” home (Fig. 8). The constructed houses, numbering fewer than 50 nationwide, featured color-anodized aluminum (purple for the siding and blue for the window grilles) and were advertisements for how aluminum could be used in residential construction. Aluminum elements in the house included the roof, fascia, lighting, diffusers, hardware, outlet covers, and even termite shields.46 This program reflected not only the desire of aluminum manufacturers to expand their reach into the residential marketplace but also the growing shift toward acceptance of color in Modern architecture, as fashions changed and shifted away from the natural colors supported by firstgeneration, high-style promulgators of Modernism to brighter possibilities. Porcelain enamel on aluminum. Boosters of porcelain enamel, a vitreous enamel of glass fused to metal (originally on enameling iron), were Fig. 6. Pattern selector for Rigidized Metals Corporation, c. 1950s. The company is celebrating its 75th anniversary in 2015. Courtesy of Rigidized Metals Corporation. Fig. 7. Yale Center for British Art, New Haven, Connecticut, 1969. Photograph by Richard Caspole, Yale Center for British Art. convinced that the material was poised for growth in the building industry, proclaiming in 1938 that porcelain enamel would take over as “the Favorite Finish of the Future.”47 Initially used for gas stations and storefronts in muted and mottled colors, porcelain enamel gained traction in curtain-wall systems in the 1950s. Architects selected it for its longlasting, nearly permanent color and strong resistance to corrosion and atmospheric weathering. Porcelain enamel was offered in a wide range of color choices, and the base metal could be roll-embossed prior to enameling to create textured finishes. Gloss, semi-gloss, 45 APT BULLETIN JOURNAL OF PRESERVATION TECHNOLOGY / 46:1 2015 process to seal UV-stable coloring media in the oxide film of the metal at the end of the anodizing process. Sealing typically involved placing the metals in boiling water to close the pores (by converting the lining of the pore walls into monohydrate form).55 Color-anodized parts were typically sealed twice: first in “hot solutions of nickel or cobaltous acetates” to hold the dyes in the oxide film and prevent leaching and, finally, in boiling water. Corrosion inhibitors could be added when maximum corrosion resistance was desired.56 Additional protection was afforded by the application of a coating of clear lacquer baked on the anodized metal. Fig. 8. Cover of Alcoa Care-Free Home, published by the Aluminum Company of America, c. 1958. The exterior featured anodizedaluminum components, including purple siding panels and iridescent blue lattice work in front of the floorto-ceiling windows. and matte finishes permitted control of reflectivity. One advantage of porcelain enamel was that bright colors could be achieved due to improved opacity, enabling thinner enamel coatings on the base metal. By the mid-1950s overall enamel-coat thicknesses on steel averaged between 0.006 and 0.014 inches and could be as high as 0.025 inches.48 In 1950 Kawneer pioneered a process for applying a low-temperature porcelain enamel on aluminum, which was sold under the trade name Zourite.49 The aluminum base allowed the enamel coats to be reduced significantly, to between 0.006 and 0.013 inches.50 One of the most innovative and technologically advanced applications was Eero Saarinen’s vivid, two-toned blue curtain wall at the IBM Research Center in Rochester, Minnesota, dating to 1956-1958 (Fig. 9). The spandrels had an asbestos-cement core and were just 5/16 inches thick. The building was described as having the “world’s thinnest wall.”51 Color-anodizing technology. Until the early 1950s the only colors available 46 for exterior applications of anodized aluminum were transparent finishes and variations of silver. Black, grey, and green colors could be achieved with chemical conversion processes, such as chromatizing and phosphatizing, which were most commonly used as a primer for painted finishes.52 Polished finishes on aluminum could be achieved with chemical polishing. While some colors of anodized aluminum could be specified safely for interior use, colors for exterior use were limited, due to the UV degradation of some color media over time with exposure to sunlight. The UV stability depended upon the stability of the coloring media, the concentration in the oxide layer, and the depth of penetration.53 Despite the limitations in durability, the Reynolds Metal Company recognized the potential of color, noting that “the metallic luster of colored anodic films has great decorative attraction,” and devoted considerable energy after World War II to improving various methods for color dyeing anodized aluminum.54 By the late 1950s manufacturers were beginning to produce a wider color range for anodized aluminum, and they continued to experiment with materials and processes that might lead to commercially viable anodized finishes with an even wider range of colors while maintaining the benefits of the protective oxide layer afforded by the electrochemical finishing process. A wider range of colors became available only with improvements in the Anodic films could be colored in one of three ways. Organic, water-soluble dyestuffs and inorganic pigments were used to create various colors.57 In this method, anodized components were dipped directly into a dye bath and absorbed the color. Colors could also be created by treating the natural oxide film with solutions that formed inorganic colored compounds. This method could create black and blue colors. In a third method, film in such colors as silvers and browns could be achieved directly in the anodizing bath with the addition of acids and other agents. Variations in the alloys also influenced the color of the anodic coating. Chromium, for example, produced a yellowish tint, and manganese created brown hues. Finally, manipulation of the metal with mechanical and chemical treatments prior to anodizing also created varying color shades and the potential for contrast. Rougher surfaces tended to appear darker after application of the Alumilite finish, making color matching of different anodized elements difficult.58 By 1956 colors suitable for exterior use included blue, yellow, black, and gold, in addition to the clear (transparent) and gray finishes. Architect Minoru Yamasaki embraced the potential of colored aluminum, stating, “Anything that increases our palette is wonderful, and if and when colored aluminum becomes absolutely a permanent thing, I think it opens up a great many fields.”59 His 1958 design for the Reynolds Great Lakes Sales Region Headquarters Build- ALUMINUM FINISHES IN POSTWAR ARCHITECTURE ing in Southfield, Michigan, incorporated gold, silver, and black anodized aluminum and was a widely published billboard for the color-anodized aluminum (Fig. 10). The rise of earth-toned anodized finishes. The wider use of colored metals in the 1950s and early 1960s eventually shifted to a more natural color palette in late 1960s and 1970s. Earth-tone colors on anodized aluminum replaced brighter colors, and clear anodized aluminum and stainless steel were used with less frequency. As earth-toned materials, such as cast-in-place and precast concrete, brick, and stone, gained prominence during the second half of the 1960s, champagne and light bronze anodized finishes, as well as medium bronze, dark bronze, and black anodized finishes, were used extensively to compliment the more natural tones in the cladding materials. This trend would continue well into the 1970s. Darker, earth-toned aluminum colors also complimented buildings constructed with other metals used in the late Modern period, including weathering steel and copper-based alloys, such as bronzes, brasses, and Muntz metal. Architects also used dark bronze anodized elements, such as spandrel panels, to contrast with lighter-colored aluminum elements, like curtain-wall mullions. Representative of this approach and the period is the Rohm and Haas Building in Philadelphia, which was designed by Pietro Belluschi and completed in 1965.60 Belluschi, no stranger to innovative uses of materials, wrapped the concrete building with balconies that also served as sunshades (Fig. 11). The sunshade latticework was constructed with dark bronze anodized aluminum and provided a frame for corrugated Plexiglas panels in a bronze hue. The predominance of the earth-toned colors of anodized aluminum may also be explained by the evolution and maturation of anodizing technology. Colors in the brown and bronze range could be created using materials and techniques that produced finishes with the greatest amount of resistance to UV-light degradation in exterior applications. Manufacturers continued to search for improved manufacturing processes that provided superior performance of coloranodized aluminum. Around 1985 electrolytically deposited anodic coatings were introduced. This process is widely used for exterior architectural applications requiring significant UV stability. Producing colors in the light bronze to black range, this process involves the application of stable metal pigments into the anodized-aluminum coating through immersion in a bath of metal salts subjected to an electrical current.61 Conclusion In the quarter century after the conclusion of World War II, the number of new aluminum metal alloys — and wide range of finishes — witnessed tremendous growth in architectural applications. Architects, intrigued by the opportunities that new industrial materials presented to achieve new forms, selected from a wide range of metals and metal finishes offered by manufacturers. At the same time, standardization of aluminum alloys increased, as the need Fig. 9. IBM Research Center, Rochester, Minnesota, 1956-1958. Photograph by Balthazar Korab, courtesy of the Library of Congress. for predictable performance grew and technological advances occurred. Manufacturers also experimented with techniques to expand the uses and ranges of finishes for architectural aluminum. Today, as Modern-era buildings require renewal with ever-growing frequency, it is important to understand the range and complexity of materials used. The postwar period was one of rapid change in the materials and metal finishes available, and the legacy of architectural production is equally rich and varied. For this reason, a strong understanding of the alloys used and how the finishes were created is essential when evaluating aluminum’s condition and in developing sensitive and appropriate repair and conservation programs. 47 APT BULLETIN JOURNAL OF PRESERVATION TECHNOLOGY / 46:1 2015 Notes Fig. 10. Reynolds Metals Regional Sales Center, Southfield, Michigan, 1958. Photograph by Balthazar Korab, courtesy of the Library of Congress. Thomas C. Jester, AIA, FAPT, LEED AP, is a senior associate at Quinn Evans Architects. He is the editor of Twentieth-Century Building Materials: History and Conservation, which was recently reissued by the Getty Conservation Institute. This paper is based on his presentation at APT’s Modern Metals Finishes Workshop held in New York in 2013. He may be reached at tjester@quinnevans.com Acknowledgements I am grateful to Robert Hotes, Todd Grover, and Christian Korab for their assistance with illustrations used in this article. 48 1. On the evolution of the relationship between structure and skin, see David Leatherbarrow and Moshen Mostafavi, Surface Architecture (Cambridge: MIT Press, 2005), 80. 2. See D. Knickerbacker Boyd, “The Standardization of Building Materials,” Architectural Forum 31 (July 1919): 31-33. On the impact of standards on the relationship between builders and architects, see Moshen Mastafavi and David Leatherbarrow, On Weathering: The Life of Buildings in Time (Cambridge: MIT Press, 1993), 20. 3. Mostafavi and Leatherbarrow, 120. 4. On the growth of aluminum as a lightweight structural material and its properties, see Aluminum Construction Manual (New York: The Aluminum Association, 1959), 9. 5. Earl P. Baker and Harold S. Langland, Architectural Metal Handbook (Washington, D.C.: R. R. Donnelly and Sons, 1947), 34. 6. John Peter, Aluminum in Modern Architec­ ture, vol. 1 (Louisville: Reynolds Metal Co., 1956), 9. 7. See, for example, Monel for Permanent Roofs (New York: International Nickel Co., 1938). Accessed from the APT Building Technology Heritage Library, https://archive .org/details/MonelForPermanentRoofs. 8. Eero Saarinen, “Six Broad Currents of Modern Architecture,” Architectural Forum 99 (July 1953): 115, as quoted in Eeva-Liisa Pelkonen and Donald Albrecht, eds., Eero Saarinen: Shaping the Future (New Haven: Yale Univ. Press, 2006), 233. 9. See Ernest E. Thum, The Book of Stainless Steels (Cleveland: The American Society for Steel Treating, 1933), 555. In decreasing order of cost, available white metals at the time included Monel (67.5% nickel, 28.5% copper); stainless steel (18% chromium, 8% nickel); nickel silver (75% copper, 20% nickel, 5% zinc); Benedict metal (57% copper, 28% zinc, 15% nickel); stainless irons and steels (18% chromium and 12% chromium); and aluminum. 10. Dennis Montagna, “Twentieth-Century Ornamental Metals and Their Care,” in Preserving the Recent Past Conference Proceedings (Washington, D.C.: Historic Preservation Education Foundation, 1995): IV-27-28. 11. Thum, 556. 12. Windows of Alcoa Aluminum (Pittsburgh: Aluminum Company of America, 1938). 13. Dennis Doordan, “From Precious to Pervasive: Aluminum in Architecture,” in Aluminum by Design, ed. Sarah Nichols (Pittsburgh: Carnegie Museum of Art, 2000), 94. 14. The stainless laminated metal product was “non-tarnishable and made of Stainless Steel 18-8 laminated over a noncorrosive base. They present exactly the same appearance as solid stainless at a fraction of the cost.” Himco Storefront Construction (Hamden, Conn.: Himmel Brothers, 1946), 2 and D1. Accessed from the APT Building Technology Heritage Library, https://archive.org/details/ HimcoStoreFrontConstruction_257. 15. Aluminum Store Fronts, 1960 Catalog (Niles, Mich.: Kawneer Company, 1959), 17. Accessed from the APT Building Technology Heritage Library, https://archive.org/details/ KawneerAluminumStoreFronts. 16. Alcoa Aluminum Handbook (Pittsburgh: Aluminum Company of America, 1957), 8. The Aluminum Association’s aluminum alloy designations created standard designations to replace old designations issued by a litany of other organizations, including ASTM, federal, military, and the Society of Automotive Engi­ neers. See Aluminum in Modern Architecture, vol. 2, 23. 17. See Peter S. Reed, “Enlisting Modernism,” in World War 2 and the American Dream: How Wartime Building Changed a Nation, ed. Donald Albrecht (Cambridge: MIT Press, 1995), 29. 18. Aluminum by Design, 240. See also, James Ashby, “Preserving a Prototype: Buckminster Fuller’s Dymaxion House,” in Preserving the Recent Past 2 Conference Proceedings (Washington, D.C.: Historic Preservation Education Foundation), 3-1-3-8. 19. Doordan, 104. 20. Robert L. Davison, “Thin, Lightweight Curtain Walls,” Architectural Forum 92 (March 1950): 94-95. See also, Aluminum in Modern Architecture, vol. 1, 24-25 and David Thomas Yeomans, “The Arrival of the Curtain Wall,” in Preserving the Recent Past 2, 3-140. 21. Aluminum by Design, 244. On Prouvé’s tectonic impulses and experimentation with aluminum, see Leatherbarrow and Mostafavi, 160-164. 22. Aluminum in Modern Architecture, vol. 1, 136. Other early Harrison and Abramovitz buildings with faceted aluminum curtain walls include the Republic National Bank (1955) in Dallas and the Socony-Vacuum Building (1956) in New York. 23. Aluminum on the Skyline (Pittsburgh: Aluminum Company of America, c. 1954), 9. 24. Ibid., 16. 25. Aluminum in Modern Architecture, ’60 (1960 Supplement) (Louisville: Reynolds Metal Co., 1958), 27. See also, Thomas Mellins, Robert A. M. Stern, and David Fishman, New York 1960 (New York: The Monacelli Press), 377-378. 26. For a detailed account of the Comsat Headquarters design and its antecedents, see Isabelle Gournay, “Comsat Headquarters Maryland Historical Trust, Maryland Inventory of Historic Properties Form,” Nov. 1, 2004. 27. “Composite Materials Attract Designers of Lighter Structures,” Steel (June 9, 1947): 76. 28. Ibid., 78. 29. On the range of composite “sandwich” construction used in mid-century curtain walls, see The Contemporary Curtain Wall (New York: F. W. Dodge Corporation, 1958), 309335. ALUMINUM FINISHES IN POSTWAR ARCHITECTURE 30. Aluminum in Modern Architecture, vol. 1, 133. 31. The Contemporary Curtain Wall, 317. 32. Robert Score and Irene J. Cohen, “Stainless Steel,” in Twentieth-Century Building Ma­ terials, ed. Thomas C. Jester (New York: McGraw Hill, 1995), 70. 33. Alcan Embossed Pattern Aluminum Sheet (Montreal: The Aluminum Company of Canada, 1956), 2. Accessed from the APT Building Technology Heritage Library, https:// archive.org/details/AlcanEmbossedPattern AluminumSheet. 34. Aluminum in Modern Architecture, vol. 1, 248. 35. In the late 1930s Alcoa’s categories for finishes were mechanical, chemical, electro­lytic oxide, electroplating, and paint/lacquer/ enamel. See Finishes for Aluminum (Pitts­ burgh: Aluminum Company of America, 1938). Today, finishes for aluminum in archi­tectural applications are designated by the National Association of Architectural Metal Manufacturers as mechanical (M), chemical (C), anodic (A), electroplated (E), vitreous (V), organic (O), and laminated (L). See Metal Finishes Manual (Chicago: National Association of Architectural Metal Manufacturers, 2006), I-18. 36. The Contemporary Curtain Wall, 127. 37. Chris Adams and David Hallam, “Finishes on Aluminum — A Conservation Perspective,” in Saving the Twentieth Century: The Conser­ vation of Modern Materials, ed. David Hallam (Ottawa: Canadian Conservation Institute, 1993), 277. 38. Aluminum by Design, 256. 39. Aluminum in Modern Architecture, ’58 (1958 Supplement) (Louisville: Reynolds Metal Co., 1958), 88. 40. Finishes for Aluminum, 37. 41. Architectural Metal Handbook, 22. 42. Aluminum in Modern Architecture, ’58, 94. 43. William Braham, “The Authority of the Natural: Color Palettes of the Postwar Period, 1948-1968,” in Preserving the Recent Past 2, 3-108. 44. Peter Inskip and Stephen Gee, Louis I. Kahn and the Yale Center for British Art: A Conservation Plan (New Haven: Yale Univ. Press, 2011), 72. 45. Aluminum in Modern Architecture, ’58, 97. 46. See http://www.midcenturia.com/2012/08/ in-january-of-1957-aluminum-company-of .html (accessed Nov. 15, 2014). 47. J. E. Hanson, A Manual of Porcelain Enameling (Cleveland: The Enamelist Pub­ lishing Co., 1937), 466. 48. The Contemporary Curtain Wall, 205. 49. “Kawneer Enamels Aluminum for Profit,” Ceramic Industry 55 (Nov. 1950): 55-56. 50. The Contemporary Curtain Wall, 205. 51. Pelkonen and Albrecht, 50-51, 198. 52. The Contemporary Curtain Wall, 127. 53. Aluminum in Modern Architecture, ’58, 94. 54. Aluminum in Modern Architecture, vol. 2, 73. 55. Aluminum in Modern Architecture, ’58, 94. 56. Aluminum in Modern Architecture, vol. 2, 73-74. 57. Ibid., 74. See also, Aluminum in Modern Architecture, ’58, 94. 58. Finishes for Aluminum, 41. 59. Aluminum in Modern Architecture, ’58, 107. 60. Rohm and Haas Corporate Headquarters, National Register of Historic Places Nomina­ tion, 2006. 61. Metal Finishes Manual (Glen Ellyn, Ill.: National Association of Metal Manufacturers and National Ornamental and Miscellaneous Metals Assoc., 2006), 1-9. Fig. 11. Rohm and Haas Building, Philadelphia, Pennsylvania, 1965. Photograph by Robert Hotes, 2015. 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