Louis Kahn was preoccupied with the play of light and shade on elemental masonry forms and with finding ways to admit light into buildings that grew out of the essential 'nature' of the construction: 'structure', he declared, 'is the maker of light'. In designing any art gallery, the control of natural light, both to illuminate the works and to ensure that no damaging ultraviolet rays reach them, is a key challenge. In Texas, with its high, intense sun, the easiest solution would have been to admit only north light, but for Kahn an interior must be in contact with passing clouds and the movement of the sun. From the outset, therefore, he explored a vaulted roofing system in which light would be admitted from above and variously baffled and reflected before reaching the art works.

The chosen section uses a curved vault, split by a central slot that allows light down to reflector. Although it makes sense to speak of the structure as 'vaults', they are more like curved beams and span lengthwise between columns. The structurally determined curve is a cycloid, the path traced by a point on a rolling circle, and the bays are 30.5 x 6.7 metres (100 x 22 feet). At their ends the vaults are stiffened by a shallow down- stand beam, and the junction between this and the walls is a tapering slot made by juxtaposing the "logical' circular geometry of the wall with the cycloid above: the unusual geometry of the structure is thereby revealed.

The museum sits in a corner of the Will Rogers Memorial Park and the galleries are placed on a platform containing the service spaces. To preserve its solidity as a support for the 'temple' above (cp. Sydney Opera House, page 126), the offices are lit from long, narrow light wells. The entrance from the car park is placed at this lower level, while that from the park is at the upper level, reached via a gentle flight of steps up to a porch that stands like a 'ruin' of the galleries. The gallery level plan is bipolar with a central entrance hall and galleries to either side. These are articulated by two light courts and the upper volumes of the conservators' rooms below, and partly occupied by the cafeteria. The spatial quality resulting from this simplest of plans is extraordinary. Looking down the vaults, the interior seems to be composed of a succession of adjacent rooms, while looking across them, the alternation of flat and vaulted spaces, and subtle changes of light, make for an extended and exquisitely differentiated volume.

From the beginning, Kahn aimed at 'rooms structured In concrete that will have the luminosity of silver', and the design of the reflector was crucial to the galleries' success. Developed by Richard Kelly, the lighting consultant, it went through several iterations before the final version, made of solid and perforated aluminium, emerged. To clad the non-structural walls Kahn chose a pale- coloured travertine, and the silvery quality was rein- forced by blasting the stainless steel surfaces of fixtures and fittings with the shells of pecan nuts to eliminate shiny highlights. The resulting quality of light, responsive to every nuance of changing conditions outside, is enchanting. Completed two years before his death, the Kimbell Art Museum is, arguably, Kahn's masterpiece and one of the major achievements of twentieth-century architecture.

Weston, Richard, Key buildings of the twentieth century : plans, sections, and elevations, New York : W.W. Norton, 2004

When the Kimbell Art Museum was officially opened to the public in 1972, it marked another aesthetic achievement in the oeuvre of Louis I. Kahn and introduced a new institution with a considerable presence in Texas, and indeed, the art world at large. Situated in a park setting, the museum's nine-and-a-half-acre trapezoidal site is adjacent to other prominent museums, most notably the Amon Carter Museum, designed by Philip Johnson, which opened in 1961.

Mr. and Mrs. Kay Kimbell, after whom the institution is named, established a foundation to erect an art museum to house their growing collection. The board of the Kimbell Art Foundation-which had been established as early as 1936-hired Richard F. Brown as director of the museum in 1965 to realize the vision of and conceive a pro- gram for the institution as well as augment its collection. Brown selected Kahn for the commission; however, the contract required that the architect collaborate with Preston M. Geren & Associates, a local architectural firm. As with many institutions that realize their first building, the program took into account the future goals of the museum, allocating vast space to the expanding art collection, which would put the institution on the map and make it one of the city's major attractions.

Kahn, who never settled for easy or first solutions, took three years to produce four design proposals for the museum. The one leitmotif running through all his proposals was the employment of horizontal cycloid roofs/ceilings. As with most of his buildings, Kahn managed to come up with features that contextualized and lent unique character to the project. The signature roofs/ceilings are just such examples, firmly associating the structure with the once rural setting of Fort Worth. Specifically, in the distance and at one time visible from the site-was a grain silo (which has since been torn down). Ideologically, one can see and better understand how the overall form of a grain silo (which is comprised of a series of vaulted forms separated by a flat surface) conceptually deplaced from its vertical condition and resituated horizontally in the landscape, becomes the framework for the roof/ceiling configuration. These cycloid forms-be they employed vertically or horizontally-are the very elements that char- acterize and contextualize the Kimbell Art Museum in its Texas landscape.

Another feature that recurs throughout the design is diffuse light let in through skylights that run the length of each vaulted ceiling. This is one of the most striking aspects of the building's end-wall elevations, which profile these repetitive roof forms. To convey the inherent differences and qualities in materials, the arch of the concrete roof/ceiling is radially offset from the curve of the adjacent travertine-clad wall. The resulting space between these curvatures a forms a transom, which allows oblique rays of light into the rooms. These rhythmic roof forms, which can be seen on two of the building's four façades, provide a lively visual impression when walking up the stepped ramp leading to the museum's main entrance.

Rosa, Joseph, Louis I. Kahn 1901-1974 : enlightened space, Taschen, 2006

Further Reading

Benedikt, Michael, Deconstructing the Kimbell: An Essay on Meaning and Architecture, Lumen, 1992