Much of U.S. history involves high-temperature thermal processing in one form or another – melting, forging or heat treating.
In October 1751, the Pennsylvania Assembly ordered the original Liberty Bell from Whitechapel Foundry in London. The London agent was asked by Assembly Speaker Isaac Norris to procure a “good bell of about two thousand pounds weight. Let it be cast by the best workmen and examined carefully before it is shipped … to proclaim liberty through all the land to all the inhabitants thereof.” The bell arrived on Sept. 1, 1752. During the first test ring, the bell cracked.
Two local Philadelphia foundry workers – John Pass and John Stow – offered to remelt and recast the bell. Believing it to be too brittle, the new bell was alloyed with an additional 1.5 ounces of copper for every pound of the bell. When Liberty Bell II was rung in March of 1753, the tone was found to be unacceptable – probably due to the higher copper content. As a result, this bell was also recast by Pass and Stow. When the Liberty Bell III rung in June of 1753, it was still found lacking in the tonal qualities of a true E-flat.
Consequently, another bell was ordered from Whitechapel Foundry in London. When this one arrived, it too was found lacking tonally. So, the Liberty Bell III remained in use at Independence Hall, and the sister bell was attached to the clock to ring the hours.
In September of 1777, as the British approached Philadelphia, all bells were removed from the city. The legitimate concern was that the British would melt the bells down and recast them as cannon. The Liberty Bell was hidden in the floorboards of the Zion Reformed Church in Allentown, Pa. In the 1820s, the sister bell was moved to Olde St. Augustine Church. As a result of ethnic violence, the church was destroyed by fire in 1844 along with the sister bell.
Historical accounts differ on the time when the Liberty Bell cracked, but it occurred sometime between 1817 and 1846. The dogleg “crack” we see today is actually a machined-slot repair ordered in 1846 so that the bell could toll for Washington’s birthday that year. The repair worked temporarily, but as the bell was tolling around noon that day – Feb. 22, 1846 – the fracture grew, putting it completely out of tune.
Why did it crack? Several efforts have been made to analyze the chemical composition of the bell to investigate this. In 1960, The Franklin Institute took drillings from the bell for analysis. In 1975, chemical analysis was performed via X-ray florescence at 10 points around the rim of the bell. The readings varied greatly – copper from 65-73%, tin from 24-30% and lead from 1.3-5.5%. This chemical nonuniformity is thought to have contributed to its eventual failure. It’s also possible there was a casting defect that led to fracture propagation. Today’s nondestructive testing techniques would most likely have helped avoid failure by more effectively carrying out the original directive of “examined carefully before it is shipped.”
Now you know that the Liberty Bell was a product of the slogan “if at first you don’t succeed, try and try again.” Unfortunately, the third try was still not the charm, but it left us with a unique visual symbol of our nation’s struggle for liberty. IH