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Tweed Courthouse, 1881
PROSOCO and Tweed Courthouse

If you think William "Boss" Tweed was dirty, you should've seen what became of his courthouse.

Completed in 1881, the ornate five-story New York County Courthouse (Tweed Courthouse) was notorious for its 20-year construction period. The corrupt business practices involved lined the pockets of the Tweed Ring, and eventually brought down the ring and its leader, Boss Tweed. The marble courthouse accumulated grime from 1881 until the first restoration work began on it in 1989.

Tweed Courthouse housed county courts through the 1920s. Newly restored at a final tab of $90 million, it's now headquarters for the New York City Department of Education. Between the 20s and now, Tweed Courthouse served as city court, family court, then municipal offices.

Restoration begins

The city commissioned Albany-based Mesick Cohen Waite Architects (now John G. Waite Associates, Architects of Albany and New York City) in 1989 to study restoring the Courthouse. Conditions were deplorable, said Lee Pinckney, project architect for the exterior restoration.

More than a century of neglect left every type of stain and soiling on the building. Air pollution deposited carbon. Sulphur from the pollution attacked the marble, creating gypsum crusts. Other airborne grime, along with biological staining, blackened the once-bright stone.

In addition, ledges, and window sills and heads were coated with bird repellent -- a sticky black substance birds don't like. Over time, the repellent soaked into the marble. After its effectiveness wore off, birds returned, coating the surfaces with guano. Contamination was deep-seated and heavily crusted.

And some exterior marble had been painted.

Mr. Pinckney explained that the project began with a thorough exterior cleaning, so conservators could clearly define the problems of each stone. Tweed Courthouse was clad in Tuckahoe marble from Westchester County in New York, and Sheffield marble, from Sheffield, Mass.

Crews washed the dirty marble with Sure Klean® 766 Masonry Prewash, followed by Sure Klean® Limestone Afterwash. The two-step system was developed for carbonate stone that's too sensitive for the powerful acidic cleaners normally needed to dissolve decades of dirt.

The alkaline prewash dissolved contaminants for easy rinsing away. The mildly acidic afterwash neutralizes any remaining alkalinity from the prewash. It heightens the cleaning effect and brightens the stone.

After scraping the guano crusts off Tweed Courthouse, workers hit the remaining residue and underlying bird repellent with Sure Klean® 509 Paint Stripper. Now known as Sure Klean® Fast Acting Stripper, 509 was designed to quickly eat through multiple layers of paints and coatings. The gel was brushed on, allowed a short dwell, then rinsed off, taking staining and soiling with it.

They used a combination of poultice and Sure Klean® Asphalt and Tar Remover to draw embedded bird repellent out of the marble.

Workers also used 509 to remove paint from Tweed Courthouse's exterior.

About 9,650 stones

With the exterior cleaned, the architects got a good look at its condition.

"We divided the elevations into 23 sections and recorded the condition of each stone in each section," Mr. Pinckney explained. "There were about 9,650 pieces of marble, with most of the projecting pieces, cornice, sills, and window heads having problems."

The stones ranged from small, 50-pound pieces of flat stone to 3,500-pound sections of cornice. Each was catalogued by size, condition, visual characteristics and more.

When the survey was through, the project team had a good idea of exactly what had to be done. About eight to 10 percent of the stone would have to be replaced. The cost would ultimately be about $20 million.

No money

Though city officials were pleased with the firm's report, they didn't have the enormous amount of cash to "green light" a total restoration effort. So work began on smaller Tweed Courthouse projects.

These projects included shoring up cracked corners of the cornice, and restoring the building's two 1911 cage elevators and its1913 copper-plated elevator. Workers brought all three into code compliance, and increased electrical power to the building. But the firm, which became John G. Waite Associates in 1995, stayed ready.

Green light

Mayor Rudolph Guiliani gave the go-ahead in 1999. Tweed Courthouse was to house the Museum of the City of New York.

Under the direction of Project Architect Nancy Rankin, cleaning was again the first step. Kenseal Construction Products, West Orange, N.J., supplied the project’s Sure Klean® 766 Limestone and Masonry Prewash, and Sure Klean® Limestone and Masonry Afterwash. Stone restoration contractor Brisk Waterproofing, Ridgefield, N.J. used it to strip a decade of airborne cgrime from about 76,000 square feet of courthouse. The cleaning substantially improved the stone’s appearance and brightness.

Inside, an insoluble white "bloom" appeared on the red, light beige and black brick interior of one of the Leopold Eidlitz-designed courtrooms following paint stripping. "We couldn't get rid of it," Mr. Pinckney said. "We called Joe Talecki from PROSOCO. We'd worked with him on cleaning the exterior." Following Mr. Talecki's advice, crews removed most of the deposit with Sure Klean® White Scum Remover.

Everything old is new again

About four million pounds of the courthouse's original stone eventually had to be replaced. Georgia Marble's "Cherokee" replaced some. Quarried in Georgia, the marble resembled the building's Tuckahoe and Sheffield cladding. And the stone of the original cornice that was removed was re-profiled for dutchman where needed.

Workers also found 125 blocks of original Sheffield marble in the closed, overgrown quarry in Sheffield, Mass. The Tweed crony operating the quarry gave the Tweed Ring big kickbacks for contracts at inflated prices.

Ironically, those transactions helped put Tweed away.

The blocks were destined for the Washington Monument. But officials refused them after Tweed was jailed in 1871. The quarry closed soon after. The blocks lay forgotten for 128 years.

Education central

In mid-March, Mayor Michael Bloomberg nixed plans for the museum to move into Tweed Courthouse. He located the city's newly formed Department of Education in the building instead.

In his weekly column at www.nyc.com, the mayor wrote that putting the headquarters of the public school system in a building as impressive as Tweed Courthouse sends the message that education "is what we value."

It is an impressive building, says Mr. Pinckney. There's no other like it. The original building is Classical Revival; its Leopold Eidlitz addition is Romanesque Revival. And yet, somehow, it all blends together well.

The best part, he says, is that the building has been returned to civic service.

This time without the dirt.