Crown Fountain

Crown Fountain in Chicago, Illinois by Jaume Plensa and Krueck & Sexton

As part of an AIA Conference in Chicago last week, various people involved with the Millennium Park project spoke about their experiences on specific park components. Mark Sexton talked about the design and construction of Crown Fountain in the park's southwest corner, a project undertaken by his firm Krueck & Sexton Architects. Initially their office felt this project would not be appropriate for them, since they are a design firm and since artist Jaume Plensa already developed a concept for the fountain. But seeing the artist like any one of their other clients, they realized that Plensa had an idea but no way of getting it done. So they took the job, aware of the detailed design work still required for the two freestanding structures and shallow pool. Sexton framed his talk on the three physical components of the fountain: glass, water, LED display.

Glass:
The fountain recalls previous artworks by Plensa, such as Honey, Milk, Water, Earth from 1999, a roughly 7' cube of glass and stainless steel that's illuminated by neon lights. But where this piece used minimal structure to give the faux, glass brick walls lightness and transparency, Crown Fountain would require a special frame to take the gravity load of the 50' tall walls, while also helping to stabilize each tower laterally from wind forces. A custom stainless steel "T-frame" was developed to hold the glass blocks and transfer the vertical load in a zigzag pattern down to its base. As well, 1/2" diameter rods anchored to the steel structure projected out to this frame for lateral stability, supplemented by triangular corner brackets. Each glass block was custom made by hand at a glass factory outside Pittsburgh. These were fitted into small sections of the frame, shipped to the site on trucks, and lifted into place, approximately seven sections per face. Mark Sexton pointed out that the glass manufacturer was able to make almost perfectly white glass, not the typically green glass that results from the iron content of glass. This clarity helps to display a truer image, but it also runs the risk of showing dirt more easily over time.

Water:
Outside of the LED faces, water is the most important element of Plesna's fountain design. The architects needed to find a way to pump and re-circulate the water, to evenly distribute the water over the fountain's top, and to create an arcing "spit" that won't knock people over, all of these standing up over time. With numerous consultants, full scale mock-ups became the norm for the project, testing the glass and LED, but also the water at each step in its journey. To deal with the aforementioned possibility of dirt, a filter is used to remove impurities from the re-circulated plaza water. The water is piped from an underground pump (at the level of, and adjacent to, the parking garage) to tubs along the perimeter parapet. A custom glass block was made for the edge, curving 90 degrees to create the impression of an invisible edge though also giving the water a gentle surface as it begins its descent. To create the effect of the faces spitting, another custom piece was created, a plastic nozzle fitted to the stainless steel frame. Via various mock-ups, the right hole size, quantity, spacing, etc. was determined so the city and the architect would not incur lawsuits for knocking over or hurting any kids getting hit with the stream.

Beyond the shaping and syncing of the 1,000 faces to the fountain and its nozzle, the physical requirement of the LED (light emitting diode) display required a lot of coordination. Composed of long-life red, green, and blue bulbs and the requisite circuitry, three major factors influenced the design of the LED wall: their support, their heat build-up, and their legibility from outside. Rather than supporting the LED wall like the exterior, as a 50' tall wall, the architects broke the wall down into a more manageable scale and size, noticeable from the exterior as subtle horizontal bands. So along the 50' height, the LED equipment is supported every few feet, not just at the bottom. To deal with the heat generated by the lights and computers, fans at the base of the fountain cool the air, the tower acting like a chimney that ventilates the air out the top. Finally, the architects tested the LED lights with mock-ups to determine the distance they need to be from the glass for legibility, eventually determined at two inches.

Though relatively small and focused, the fountain is a complex project that one appreciates more given its short 18-month timeframe for development and construction. Although typically credited to Plesna, it's evidently a complex project that required many specialized parties to achieve the intended effect.

Chicago Tribune graphic