Alabaster Gleams in Cathedral
Its sand-colored concrete walls loom over Temple Street like an urban butte, and tons of marble, bronze and limestone gleam within. Yet, in the end, there’s no earthly element in the new Cathedral of Our Lady of the Angels that matters more than the alabaster.
Its job, basically, is to suggest the presence of God. When the cathedral’s first rank-and-file visitors step in on Sept. 3, they’ll find alabaster cut into translucent panes left, right and center, 27,600 square feet of it, designed by architect Jose Rafael Moneo to filter sunbeams into sepia tones, and to stand in for the stained glass that Catholic worshipers have admired for centuries.
Nobody in North America, authorities agree, has ever used so much of this strange stone this way. And as the cathedral’s builders readily concede, there are some sensible reasons for that. The tale of how this cathedral got its windows is, at bottom, a chemistry equation. But it also hints at the high ambitions of the cathedral’s creator and patron, and it reveals the hard work that begins after an architect’s biggest decisions and the surprises that crop up, even on a closely monitored $163-million construction site.
If you have driven through downtown Los Angeles on the 101 Freeway, you have seen the cathedral’s sandy walls and the tall cross formed by the concrete, alabaster and glass behind the altar. From the floor of the cathedral, the alabaster makes a bigger impression--11,800 panes, each sliced to a thickness of 15 millimeters (about 5/8 inch) and naturally veined like a vast, living membrane.
“It’s a curious material,” said C. Terry Dooley, senior vice president at Morley Construction, who has supervised work on the cathedral for six years. “It’s found in big globules, lying around at random in fields and on hillsides. They lug them back into the shop, clean all the dirt off, and then try to slice them. It comes in weird shapes, and you have to slice a whole lot of pieces to get clean integral pieces of this size. They break a lot of them. It’s a fairly inefficient material.”
Chemically, alabaster is hydrated calcium sulfate, typically found in boulders made of sedimentary rock formed as salty water evaporated. Etruscan mourners put the ashes of their dead into alabaster amphorae.
Sculptors today like it because it’s easy to carve, with veins that might run red, green, gold or gray.
“It’s almost like marble that’s not done yet. It needs temperature and pressure for a few million more years,” said Randy Fulton, project management consultant for the archdiocese’s project management firm, Stegeman & Kastner.
Alabaster is in the Vatican (pieced together to form a dove, high up behind the altar of St. Peter’s Basilica). It’s in the new Martha Stewart catalog (7-inch-high vases for $28) and the Getty (vases again, not for sale). It’s in the collected works of Emily Dickinson (who once wrote a poem titled “Safe in Their Alabaster Chambers”), and in quarries and churches scattered through Italy and Spain. It’s also in the fourth verse of “America the Beautiful” (“Thine alabaster cities gleam ...”).
Yet until this cathedral, North America had never seen this much alabaster outside a quarry. Why? Because it’s difficult to quarry, it’s soft and delicate, it crumbles at high temperatures, and if you put it directly under a hard rain for long enough, it might dissolve.
Vulnerability to
Heat and Moisture
“If you bear down pretty good, you can scratch it with your fingernail,” said Stan Jones, owner of Colorado Alabaster Supply in Fort Collins. “It’s really good for small, detailed pieces.”
Jones has quarried and sold alabaster since 1969, selling mostly to sculptors and craft workers. If you put too hot a bulb in a lamp with an alabaster shade, Jones said, “you bake the water out of it, and pretty soon the whole thing loses its translucence and looks like chalk.”
The stone’s vulnerability to heat, said Douglas Hammond, a professor of earth sciences at USC, is the result of a chemical structure that includes two water molecules. Specific results can vary, depending on humidity and other factors, but generally, when pure alabaster’s surface temperature reaches 136 degrees--a level often surpassed when heat accumulates on roofs and exterior walls on hot days in L.A.--the water molecules separate from the stone and it goes opaque and chalky. Basically, it becomes gypsum, a material found in common plaster. As heat rises further, it disintegrates. Alabaster’s chemical structure makes it vulnerable to moisture, too. In fact, Hammond says, with enough direct exposure to sustained rain, “it would eventually start to dissolve.”
From the start, these traits have been well known and much discussed in the offices of the architects, engineers and contractors working on the cathedral. But they amount to only part of the picture.
For all his worldliness as an architect--he won the prestigious Pritzker Prize for architecture in 1996, sits on the faculty at the Harvard Graduate School of Design and prides himself on largely reinventing his style for each job--Moneo’s affection for alabaster can be traced to his birthplace in northern Spain, where many churches dating back centuries include alabaster windows and other details.
In his 1992 Miro Foundation building on the Spanish island of Mallorca, Moneo placed moisture-sealed translucent alabaster panes between concrete louvers as a device to bring in light but screen out the view of surrounding buildings.
In Los Angeles, the architect reasoned, alabaster would evoke church history and harmonize with the cathedral’s other earthy materials. The fragile stone’s filtered light, Moneo said, would serve as “a metaphor for mystical experience and for the presence of God within the church.”
And then there was the bottom line. The archdiocese has said it spent $20 per square foot on the stone in the cathedral--about $660,000, excluding labor. Even with the careful handling that alabaster requires, said project management consultant Fulton, its cost is a small fraction, perhaps one-tenth, of what traditional (and labor-intensive) stained-glass windows could have cost.
But what about heat and weather? The specialists at Morley Construction and executive architects Leo A Daly wondered. “There was a lot of concern over the alabaster,” recalled David Campbell, a designer in Moneo’s Los Angeles office.
Morley Construction’s Dooley remembered taking detours to obscure churches on his European vacations in the late 1990s, just to see how the old alabaster had held up. It’s impossible to know all the factors involved, Dooley said, but some of those sunbaked panes are “pretty dark now, and they look gloomy. The last thing we want is gloomy.”
Experiments to Make
the Material Hardier
One of the team’s first proposed solutions was to protect the alabaster by laminating it with glass. But that quickly proved a nonstarter; the laminating process itself generated such heat that the alabaster went solid white.
Next, the designers and builders made appointments in 1997 and 1998 at the Smith-Emery Testing Laboratory in Los Angeles, and set up a science project. First, they put samples of raw alabaster, sealed alabaster and glass-sandwiched alabaster into an oven. Then, said Dooley, researchers ran the oven “through cycles as though the alabaster was being heated by the afternoon sun in L.A. They went back down cool, then back up, then back down.”
In too many cases, it was Stan Jones’ lampshades all over again: dried-out and clouded samples. With unsealed alabaster, recalled Nick Roberts, project manager at Daly, the trouble began just above 110 degrees--unacceptable in a cathedral that’s supposed to last 300 years. Fulton, who was also on hand for the testing, used words like “brutal” and “abysmal” to describe the glass-sandwich results.
The lesson of the testing, all sides agreed, was that the alabaster needed more protection. The project’s mechanical, electrical and plumbing engineers, Ove Arup and Partners, used computerized airflow modeling to design a sort of double-glazed window system: First, to take the brunt of the sun, they set up an exterior membrane of laminated glass embedded with ceramic material to screen out roughly half of the incoming light. (Look up at the stairstepped exterior windows from Temple Street and you can see the herringbone pattern.)
Then, beneath that exterior but outside the steel-and-aluminum frame that would hold the alabaster, they created a ventilation gap 1 to 7 feet wide to let moving air carry away heat that would otherwise accumulate. In theory, the alabaster challenge was solved.
In practice, however, there was still an unprecedented amount of alabaster to be found, shipped and placed. Acting on a recommendation from Moneo, who lives in Madrid, the archdiocese investigated and made a deal to buy its alabaster from Arastone, a quarry in Zaragoza, in northern Spain.
Like butchers slicing salami, workers at circular saws shaved the pieces down to a thickness of 15 millimeters, then cut them into six standard sizes. The smallest panes were cut about 13 inches high and 3 inches wide; the largest, 34 inches by 24 inches. The veining was limited to four hues (roughly, grayish, yellowish, whitish and reddish), and soon after they were cut, the panes were coated on all sides with sealer.
Then came inspection by a different European stone company, hired by the archdiocese to evaluate samples of the alabaster before it left Spain--conducting stress tests and looking for fractures, veining problems and inexact dimensions.
Planning conservatively, the archdiocese ordered more than 33,000 square feet of stone, allowing for 10% of that to break in transit or on site, planning to set aside another 10% for future years.
It arrived, on time, in six shipping containers, snugly packed in crates, panes wrapped in foam. Benson Industries Inc. of Portland, Ore., the subcontractor chosen to handle the alabaster and exterior glass, began by putting up the framework to hold the panes. Then it was up to half a dozen workers to set the alabaster within its frame, matching a pane-by-pane pattern set by Moneo to create a calculated “random” effect.
They started in June 2001. Using electric hoists purchased specifically for the task, they carried no more than 200 pounds of alabaster up on each trip. Five months later, 11,800 panes of alabaster had been placed aloft. In the “lantern” area above and behind the altar, where heat accumulation is greatest because many alabaster panes lie horizontally, designers used smaller panes and added a thermostatically controlled cooling system. Installers also added a 2,800-square-foot underpinning of safety glass above the altar area, so that, if a pane of alabaster should weaken, it wouldn’t fall.
“We handled it very much like we would handle a piece of glass,” recalled Michael P. Flucke, senior vice president for Benson Industries. “But the stone was not nearly as fragile as everyone expected.”
In fact, when the numbers were tallied, in all the packing, shipping, hoisting and placing, fewer than 1% of the panes had been broken or rejected.
There was so much stone left over, Flucke said, “it became a little problem. Nobody expected to have so much.” The archdiocese wound up with about 5,000 square feet of extra alabaster on its hands.
The panes in the cathedral, their installation guaranteed by Benson Industries for 10 years, have been aloft in their aluminum frames for about a year now. They endured the heat wave of late June and early July, when temperatures exceeded 90 on the ground, with no hints of any heat damage and no breakage, contractors said.
“The hottest part we have is that lantern skylight. On our hottest days, it’s about 110,” Fulton said. “If it got over 140 degrees in there, we’d put in more ventilation.”
‘A Journey to
and Through Light’
Stepping into the cathedral, a visitor doesn’t get the full alabaster effect right away. The path in leads through sculptor Robert Graham’s 25-ton bronze main doors, then up a gently sloping ambulatory that leads to the rear of the church. At the end of the walkway comes a right turn, and it’s then that a visitor sees the full volume of the building’s interior. Cardinal Roger M. Mahony has called the architectural experience of the cathedral “a journey to and through light.”
The alabaster signals completion of that journey. Filtering down to the wooden pews and Spanish limestone floor of the church, the light changes by the hour, sometimes yellowish, sometimes darker. By night, the effect turns inside out, and the building’s interior lights shine through to make the church a sort of beacon. Regulars in the building say they prefer the late afternoon, when the hue goes more orange, and the evening.
Even then, the effect is nothing like the traditional varied and saturated colors of stained glass, and church officials say they expect to hear from traditionalists about that. (Those traditionalists do have the option of stepping down a level. The old stained-glass windows from the nearby deconsecrated former cathedral, St. Vibiana’s, have been relocated to the new cathedral’s mausoleum, where they’re illuminated from behind with fluorescent lights.)
Meanwhile, the archdiocese has found a place for its leftover alabaster. After a moving job that took four days of loading, about 2,000 stone panes sit crated in a storage facility in East Los Angeles.
“So,” Flucke said, “if they want to build an addition ...”
