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Gold Coating Proves a 24kt Failure

Friday, June 20, 2014

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A mysterious coating failure is causing 1,200 square feet of gold—a new, half-million-dollar paint job—to crack and peel on a massive historical monument in New York City’s Central Park.

The 24-foot-tall rendering of Gen. William Tecumseh Sherman, sculpted by the late Augustus Saint-Gaudens in 1903, was just regilded last year.

But officials say something has gone wrong with the Civil War legend's coating, and they have no idea what.

Central Park Conservancy
Central Park Conservancy

Gilt applied last year on the Gen. Sherman statue in Central Park is already cracking, and in some areas "almost peels off like an orange."

The sculpture sits on the Grand Army Plaza, the gateway to the 843-acre park on Fifth Avenue, and is cared for by the Central Park Conservancy.

The statue shows Sherman on horseback, accompanied by a bronze figure of Pomona, goddess of abundance. After the Civil War, the general moved to New York City and rode his horse and carriage through Central Park daily, the Conservancy reports.

$500K Coatings

The statue underwent rehabilitation last summer, when it was cleaned and coated with 23.75-karat gold leaf, The New York Times reported at the time.

Although The Times reported that the gold leaf would be topped with three coats of polyurethane to protect the gilding, a different approach was taken, said Michael Kramer, founder of The Gilders' Studio, of Olney, MD, which completed the project.

Kramer said the statue "was toned, then coated with a urethane system," not with polyurethane. "It was, in fact, an aliphatic urethane system which had been rigorously tested in the lab and the field."

In any case, the $500,000 project starting coming undone by October, when conservancy officials first noticed cracks forming at the base. First, they thought it was a moisture problem, but it continually got worse.

The Gilders' Studio

Regilding the statue will cost hundreds of thousands of dollars, said Mike Kramer of The Gilders' Studio, which completed the original project last year.

"The gold was just not adhering to the substrate as it's supposed to," Christopher Nolan, the conservancy's vice president for planning, design and construction, told the Times on Wednesday (June 18).

"Something had gone wrong in the way the materials interact," Nolan said, adding that in some areas, the coating "almost peels off like an orange."

'We Knew it Was Systemic'

According to its website, The Gilders' Studio provides interior and exterior gilding, sculpture conservation, painted finishes and murals, and similar services.

Kramer took a look at the Sherman cracking (called crazing) in April.

"Even where there was no crazing evident to the eye, when you put it under the microscope, you could see it. So we knew it was systemic," Kramer told The Times.

Expensive Failure

The Gilders' Studio has accepted responsibility for the problem and will pay for the regilding, which Kramer said "would cost hundreds of thousands of dollars."

The Gilders' Studio

The Gilders' Studio's conservation portfolio includes Winged Victory, the 1st Division Memorial, in Washington, D.C. Both this and the Sherman statue were regilded in 23.75-karat gold leaf.

Officials do not know what caused the failure, but materials used were tested in the laboratory and on site, Nolan said.

One possibility is an issue with the adhesive material, called size, that was used. Or it could be the urethane the conservancy opted to use to make the surface more resistant to pigeon damage than traditional wax.

Kramer told The Times that the size that was successfully tested came from a different lot than the size that was actually used. Perhaps, the report said, there was some discrepancy.

According to the conservancy, Sherman will be regilded this summer. This time, the urethane will be cut out, as will the intermediate glazing.

Coating Trials

This isn't the first time that "Uncle Billy" Sherman's coating has caused a problem. The prior gilding job, in 1989, was roundly reviled because it was so bright and shiny, The New York Times reported then.

The critics included Richard J. Schwartz, the philanthropist who footed the $116,500 restoration tab.

Lear magazine publisher and Central Park neighbor Frances Lear decried the "vulgar, garish gilt that seems just a horror.''

Park officials noted that the more subdued green and black patinas of nearby statuary signaled not artistic enhancement, but extensive corrosion.

'What should be remembered is that what you're seeing in that blackish patina is disintegration," said Paul Gunther, spokesman for the Municipal Art Society, "and if you don't do something, it will ultimately just fall beyond repair."

Nevertheless, a lightly tinted wax was applied in 1996 to tone down the shine, The Times noted.

This post was updated at 10:46 a.m. ET June 20, 2014, to reflect additional project details provided by Mr. Kramer.



Tagged categories: Adhesion; Coating failure; Corrosion protection; Cracking; Gilding; Historic Preservation; Historic Structures; Monuments; Peeling; Program/Project Management

Comment from Edward Kelly, (6/20/2014, 6:48 AM)

Personally I think the cleaning process should be closely looked at because if a residue left behind by many of these processes is not completely and thoroughly removed, you will find the results your are getting.

Comment from Michael Kramer, (6/20/2014, 7:22 AM)

If this article would have accurately reflected what was printed in the Times, you would have read the problem was a loss of adhesion between the gold leaf and size layer, not between the primer and bronze. Unfortunately, JPCL did not make much effort to be accurate. If they had, you would also have read the sculpture was toned, then coated with a urethane system. Nowhere was polyurethane mentioned, or used on the sculpture. It was, in fact, an aliphatic urethane system which had been rigorously tested in the lab and the field.

Comment from Dudley Primeaux, (6/20/2014, 8:25 AM)

Ah well from a “chemist” perspective, the term “urethane” is short for “polyurethane” and is a broad description. Aliphatic polyurethane (or could have said aliphatic urethane) would be the specific type of urethane / polyurethane polymers that are noted for excellent UV resistance / UV color stability, as opposed to aromatic polyurethane (aromatic urethane - same) which have poor UV color stability.

Comment from Tom Schwerdt, (6/20/2014, 8:39 AM)

Hm, if Michael is insistent it isn’t a polyurethane, perhaps the explanation is the applicators never used a crosslinker. No crosslinking, no "poly." Yes, that's a bit tongue-in-cheek. Anyway, I agree with Dudley on terminology - and he's the expert in this area. Urethane is most commonly used as a shortened version of polyurethane.

Comment from Jerry Trevino, (6/20/2014, 8:42 AM)

Did the gold come from the South?

Comment from Dudley Primeaux, (6/20/2014, 9:05 AM)

Ha Jerry, that's funny... Getting their revenge I guess. Ah but could be from all those gold coins that couple in CA found burried in the yard..

Comment from Mary Chollet, (6/20/2014, 11:04 AM)

The New York Times reported in June 2013 that the regilding project would include three coats of polyurethane "to protect the gilding from ultraviolet rays and pigeons." Mr. Kramer's comment indicates that a different approach was later taken. The article has been updated to reflect his additional information.

Comment from Tom Schwerdt, (6/23/2014, 8:15 AM)

Hm, any clarification with what they mean when saying the gilding "was toned" - did they use some sort of traditional adhesive or coating, then try to cover it with polyurethane? That could well be the recipe for adhesion failure, depending on what was used for the toning. Solvents or simply crosslinking stress from the polyurethane overcoming the weak adhesion of the toning. A traditional wax protective layer would have neither issue. Mixing traditional and modern coatings/adhesives can cause big problems.

Comment from Robert Lodge, (12/30/2014, 12:15 PM)

Gold leaf is adhered to a partially oxidized drying oil film on the substrate. The applied leaf becomes a barrier, slowing the completion of oxidation and hardening. The curing of acrylic urethanes imposes stresses on underlayers - hence the advisability of performing adhesion tests (ASTM D 4541 or cut tests) before overcoating. Three applications of urethane clear may have simply overcome the oil size adhesion or cohesion. I was involved in application of an acrylic urethane clear over gold leaf in an attempt to prevent birds scratching off the leaf. But the owner was asked to accept responsibility for any failure due to insufficient performance histories of this coating method (and owner accepted) In addition, about four months of warm temperatures additional oxidation of the oil size partially sealed off from air by the leaf was allowed. Its been a year and so far no disbonding. Th power of the pull of curing epoxy or urethanes should not be underestimated.

Comment from Warren Brand, (1/5/2015, 9:06 AM)

I'd like to hear more about the specifics of the testing. And yes, what does "toned" mean?

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