Louis Kahn gave to architecture new and timeless concepts of shadow and light, texture, structural solids and voids, and the expressive power of sym- bolic geometry from minimal to monumental scales. Kahn transformed imperfections to new concepts of perfection. In concrete work he kept the bolt holes and the ridges between form work as the „marks of how it was made.” To express the integrity of the edges of brick, stone and wood when they come together, he recessed the mortar between bricks, between stone and stone, and recessed the caulking between stone and wood. Kahn said, „The joint is the beginning of ornament.”  These recessed „shadow joints” at the Weiss House (1947-49) expressed the stones’ irregularity and the straight edge of wood with a shadow joint of caulking between. During the process of construction, Kahn and I often visited the site. In discussions with the Weisses during picnics, many of these concepts became clear.
Kahn’s concept of the shadow joint later evolved into the „light joint.” Kahn said, „Paestum is the time when the walls parted and the columns became.” Here at Stonehenge and at Paestum our daughter Alexandra, aged 11, gives scale and ornament to ancient light joints.
 At the Yale Art Gallery (1951-53), Kahn’s first prestigious building, a light joint is created at the roof above the triangular stair within a cylinder. The protective woven wire mesh at the stair rails, al- though very strong, appears to be almost dissolved in light. (I discovered the material in a conveyor-belt factory, going by myself to a deserted industrial area of Philadelphia.)
The close-packed tetrahedron/octahedron geom- etry of the Yale Art Gallery ceiling embodies the con- cept of a „breathing ceiling” that is still at the cutting edge of architecture today. A view of the framework demonstrates the hollows that harbor a network of heating/cooling ducts and multiple lighting sources, all with continuously accessible controls. The symbolism of the geometry can be found in the Pythagorean concept of the five Platonic solids as the shape of the smallest particles of fire, air, earth, water, and the cosmos. The tetrahedron (fire) with the octahedron (air) are the sources of lighting, heating and cooling.
 Before work began on the Yale Art Gallery, in 1949-50, I had designed as an independent, unpaid exploration an elementary school with a tetrahedron/octahedron structure that „grew” its own supporting columns from the same con- tinuous geometry. The spanning structure itself thickens with added layers diminishing horizontally while increasing vertically toward the three points of support. Each classroom is part of a larger tri- angle, forming a three-classroom unit with utilities and circulation at the center. The geometry of the elementary school was the same as the geometry that was ultimately used in the Yale Art Gallery ceiling. In fact, Kahn used the model I built to try threading the Yale Art Gallery ductwork through the space frame.
Although the elementary school was never built, it stimulated my concept of building a total space frame house, hollowed out for living space within the structure. In 1951-53, at the same time that Kahn and I were working on the Yale Art Gallery, I designed such a house for my parents. By turn- ing the geometry so that the squares which occur in the octahedrons were in the horizontal plane, I was able to make a more familiar rectangular plan, and even create the pitched roof that my father wanted–but that I had considered old-fashioned and sentimental while under the Bauhaus influ- ence when I was a student at the Harvard Graduate School of Design. The house survived 150-mph winds during Hurricane Hazel (1954) while roofs of neighboring buildings were blown off. The house is, I believe, the first use of a continuously con- nected space-filling geometry hollowed out or extended to make living space.
 The same geometry was used, but with triangles in the horizontal plane, for Kahn’s and my proposed City Tower (unbuilt, 1952-58). The first, lower, ver- sion in which tilted columns act both as beams and as columns, was my independent unpaid explora- tion which I hoped would interest Kahn. He „saw its essence,” and we worked together on the higher version of the tower, with Louis Kahn acting officially as „Architect” and I as „Associated Architect.” It is still unbuilt, although I believe its structure would resist collapse from impacts as strong as those which destroyed the World Trade Center on 9/11, since the triangle is an incompressible form and the structure is totally triangulated and connected. With the breaking of any joint, the stresses would simply pass to other joints. Kahn extended the concept of hollowing structure to his proposal of a „hollow capital” where three tilted columns from below are connected to three columns above. Here the hollow capital becomes more than a joint; it provides an occupiable space for maintenance and control of utility connections. Kahn compared the effect of our helical tower seeming to be in continuous motion with the Seagram Building as „a lady wearing corsets.”
 At the Trenton Bath House (1954-56) Kahn’s concept of the hollow capital for our City Tower was expanded to the idea of a hollow column. We used 8-ft square columns for walk-through baffled entrances to dressing areas, for the director’s pool- side office, for stairs down to the chlorinating plant, and for toilets and storage. The roofs appear to float above the columns, although they are supported by delicate steel pintles imbedded in the concrete caps on the hollow columns. The space between the roofs and columns is a light joint in the vertical plane when the roof edge is lined up with the walls. If the walls are beyond the roof’s edge, the light joints are, in effect, skylights. There are also square openings at the apex of the hipped roofs. At the time, Kahn did not call them „light joints.” The sim- ple circle of the spray pool within the square court recalls the philosopher’s „squaring of the circle.” Kahn expresses this symbolism more powerfully in his „cubing of the sphere” at the Exeter Library in New Hampshire.
 In the third floor addition to my own house in Philadelphia (1965-68) I built a 15-foot high, eight inch wide light joint. The triangular windows around the bed loft above also act as light joints for the stu- dio drawing tables below. The most intimate space of the bed loft offers the most expansive views of Philadelphia.
At Kahn’s Salk Institute (1959-65) in La Jolla, Cali- fornia, the great court seems to connect directly with the Pacific Ocean. Its narrow channel of water becomes a light joint by day and a shadow joint by night, as it seems to disappear into the Pacific. The Landcape architect Luis Barragan called the Salk court a „façade to the sky.” Kahn’s Salk Institute is a magnificent example of his capacity to express symbolic power.
 In the Kimbell Museum (1968-74) Kahn devel- oped an extraordinary range of scale of shadow to light joints. Shadow joints occur between the concrete structure and the travertine infill, be- tween steel window frames and the concrete walls, between interior door frames and their panel infills. Light joints occur between the cycloid curves of the vaults and the beautifully tensioned infill curves at the wall ends of the vaults. The courtyards can be thought of as very large light joints, each differenti- ated by the color of its plantings. The dominant light joints are 100-ft long cleavages in the vaults which are thereby split into cantilevers from the side walls. Direct light is allowed through small perfora- tions, and most of the natural light is reflected onto the ceiling where the cycloid curve distributes it dynamically (in contrast with the semicircular curve that only reflects to a center point). Although the sun’s ultraviolet rays are known to be damaging to art treasures, tests at Kimbell happily confirm the safety of its use of natural light.
 The Capital Complex at Dhaka (1965- after Kahn’s death in 1974) is a powerful symbol for Bangladesh that appears even on postage stamps and on the backs of rickshaws. The large assembly hall is surrounded by a mosque and meeting rooms of square and cylindrical towers that also give shade and cooling air flows. Buildings for living quarters compose a geometry of spaces that build up to the most powerful monumentality of the capital that is surrounded by water in the rainy season, defining and enhancing that island of monumentality.
I started working for Stonorov and Kahn in 1945, moving with Kahn to his first independent practice in 1947. We appear here in his new office which was shared with a firm of structural and mechanical engineers. As architect and teacher, Kahn gave profound thought to the creative process. He often said, „You can’t eat pencils and spit ideas.” While teaching at Yale, Kahn wrote me a letter in which he made a diagram of his concept of the creative process. His „Nature of Space, Order, Design” idea was a response to the fact that students were simply following existing examples with a few changes in order to maintain self-respect. Kahn had them throw out their schemes, become open to all the possibilities of time and space, and give up some ego to ask „what the space wants to be.” Rather than superimposing an order or idea, Kahn asked students to be more open to a profound concept that may come to them — a breakthrough to „Order” which would move towards the „Design” phase of meeting needs of budget, site, function, structure, and materials.
Louis Kahn’s understanding of the creative process has an extraordinary correspondence to my cyclical theory of creativity that includes the following stages:
- The challenge
- Looking at history or precedent
- Being open to the „Nature of the Space” or „what the space wants to be”
I have found five similar cycles of form and energy that proceed from simplicity to complexity and reach a breakthrough to another level of simplicity. Two cycles compare the invisible inner structure of the Deoxyhemoglobin molecule with the vast structure of the Dumbell Nebula in cosmic space; a third cycle shows the four forces of the universe, a fourth shows in cyclical form Carl Jung’s psychic process of individuation; and a fifth cycle shows the changing empathy for styles in art and architecture.
From castled island childhood of windmill energies
And marked by scars from glowing coals
That may have sparked his creative fire,
Exploring color, light and shadow, structural voids
Finding monumental strength of geometry,
Louis Kahn gave new expressive power and timeless
To an architecture of matter, light, and energy.
Anne Griswold Tyng, PhD, FEAIA, received her Masters Degree in Architecture from Harvard University with the first group of women allowed to study in the architectural school. For 30 years she worked in Louis Kahn’s office, first as an assistant architect, then as an associate, and finally as a consultant. She also worked closely with Kahn on the Yale Art Gallery, Trenton Bath House, and Erdman Hall Dormitories at Bryn Mawr College.
In 1975, Tyng was awarded Fellowship in the AIA and the distinction of Academician in the National Academy. She has published numerous articles that have been translated into Italian, French, German, Spanish, Japanese and Farsi and she edited/authored the book Louis Kahn to Anne Tyng: The Rome Letters 1953-1954 (Rizzoli, 1997). Tyng taught at the University of Pennsylvania for 27 years and has lectured internationally on her own work and the work of Louis Kahn.
Anne Tyng participated in Louis Kahn Days in Saaremaa as one of the main lecturers.
Illustrative images spring from Anne Tyng.