Copper in the Arts

October 2021

History Cast in Copper

By Courtney H. Diener-Stokes

IMG_2012.JPGThe Liberty Bell at Independence Hall in Philadelphia, PA.
Photo courtesy of The National Park Service.

Copper is a standout in the history of America’s most famous bell, the Liberty Bell, best known for being a symbol of freedom and justice that bears the anti-slavery inscription: “Proclaim Liberty Throughout All the Land Unto All the Inhabitants Thereof.”

The Bell has a chronology that dates back to October of 1751 when the Pennsylvania Assembly directed that a bell for the Independence Hall tower, previously known as the Pennsylvania State House, be ordered. The bell arrived less than a year later after being cast at London’s Whitechapel Bell Foundry. The composition of metals used to make the Bell wasn’t unique in the 1700s.

“A mixture of predominantly copper with a portion of tin was standard for 18th century bells,” says Karie Diethorn, Chief Curator, Independence National Historical Park, National Park Service, US Department of the Interior.

Diethorn explains that the Liberty Bell’s current composition, 70% copper, 25% tin and 5%  a combination of gold, silver, lead and zinc, is that of subsequent castings. The Bell, which is approximately four feet in height, was recast twice in Philadelphia in 1753 by John Pass and John Stow. The third casting represents the Bell we know today. 

“It’s believed that those trace elements in the Liberty Bell resulted from what Pass and Stow had on hand at the time of their second casting of the bell -- they literally threw stuff into the molten bin,” she says. 

Diethorn says it is likely that Pass and Stow thought the addition of silver might improve the Bell’s tone. It was recorded in the Bell’s chronology provided by Diethorn that the sound of the Bell was rejected on more than one occasion.  

“In this small amount that wasn’t actually possible,” she says of the silver that was used. 

According to Diethorn, while Pass and Stow were hired to cast and recast the Liberty Bell, their lack of experience might have had a negative impact on the Bell. 

“This project was their first large-scale one,’ Deithorn says. “Their lack of experience may have been a factor in the Bell’s demise.”

It has been speculated that the composition of the metals used to make the bell had an impact on it cracking.  

“Too high a portion of tin in the mix of a bell casting makes the final product brittle,” Diethorn says.   

She discusses a process that was used later to address the Bell’s crack. 

“The 1840s response to the Bell’s “cracking’ was removal of the metal along both sides of the crack -- a process called stop drilling,” she says of the method that can be  used to stop the growth of a crack in a piece of metal. 

Over the past two centuries, The Liberty Bell has quite a travelled history. Before World War I, the Liberty Bell went on tour around the United States, but this ended after it became clear the Bell could not weather the journey, and cracks began to form. Today, it resides at the Liberty Bell Center in Philadelphia, where it is occasionally tapped to mark special occasions, drawing more than one million visitors every year.


Liberty Bell Center, Independence Hall, 526 Market St., Philadelphia, PA, (215) 965-2305

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