A Precious Tip

On September 29, 2011 · 7 Comments

The Washington Monument has been in the news quite a lot lately, as experts examine damage resulting from the 5.8 magnitude earthquake that struck the District of Columbia on August 23, 2011. The thought of people rappelling down narrow masonry walls for hundreds of feet searching for cracks seems daunting, as described in this video from the Associated Press:



The monument has an interesting history, most of which I’ll gloss over quickly before focusing on the one item that I’ve always found particularly fascinating for some unknown reason.

Conceptually, the thought of a monument recognizing George Washington dates all the way back to the Continental Congress of 1783 although nothing much ever happened with the idea at the time. It finally began to crystallize in 1832, the 100th anniversary of Washington’s birth, with the establishment of a Washington National Monument Society. A design competition followed in 1836. However, a cornerstone wasn’t laid until 1848, and by then a Washington Monument in nearby Baltimore had already stood for nearly twenty years. History shows that things tend to move slowly in the highly-politicized spheres of Washington, DC, a trait all common today.



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The first Washington Monument – the one in Baltimore, Maryland

Construction sputtered along until the Society exhausted its donated funds in 1854, leaving a stump one-third finished as an eyesore for another twenty-five years. Congressional funding solved that problem in 1879 and the monument was finally completed and dedicated in 1885.

That’s all great, but I’m most interested in a feature that’s generally difficult to see. It’s been made more visible by all of the close-up photographs of rappellers securing their lines to the top of the monument, as in this example once again courtesy of the Associated Press.


Top of the Washington Monument

Pay careful attention to the very tip of the Washington Monument. Several spikes acting as lightning rods appear like thorns around a small metallic pyramid. Those spikes were a latter addition. The "pyramidion" was the original lightning rod. It is 97.8% pure, composed of a shiny material that was quite rare and unusual when placed atop the monument: it’s made of aluminum.

The old story, the urban legend, is that only the rarest, most expensive metal available on the planet was good enough to cap the Washington Monument. That’s the story I grew up with, and that’s the story one is likely to hear from the tour guides. It’s repeated as fact ubiquitously. However it’s largely been debunked, for example by an article in JOM, a publication of The Minerals, Metals & Materials Society ("a technical journal devoted to exploring the many aspects of materials science and engineering")


High Atop a Washington DC Rooftop
Yours Truly on July 4, 2009

Aluminum was rare not because of the scarcity of raw materials that went into it but because it was horribly difficult to produce. Only one foundry produced aluminum in the United States, the William Frishmuth Foundry of Philadelphia, and his annual output at the time was about 28 kilograms (62 pounds).

Rare perhaps, but it had a value approximately equal to silver, a much more commonly-available material. The base of the metalic pyramid measured 140 millimeters (5.6 inches) on a side, with a height of 230 mm (8.9 in), made of solid aluminum with a total weight of 2.83 kg (100 ounces). That’s a good chunk of aluminum but even then it didn’t command an astronomical price. The construction budget could accommodate it.

Why was it no more expensive than silver given its scarcity? It goes back to a simple rule of economics: the supply was very small but so was the commercial demand. Improved smelting techniques developed a few years later allowed Aluminum prices to drop like a rock, thus stimulating demand. The Washington Monument may have helped this trend tangentially since the aluminum cap had been featured prominently in the news of the time, the first instance when many citizens had ever heard of the "exotic" metal. Remember that the next time you drink a soda from an aluminum can.

The Frishmuth Foundry cast the aluminum pyramid. It was one of several metals considered for the project, and selected primarily because it was shiny, durable and wouldn’t tarnish. There wasn’t a strong push by the builders to require or demand aluminum for the cap. Frishmuth wasn’t even sure he could cast something so large, the largest Aluminum casting attempted anywhere at the time. Frishmuth even arranged a backup plan if necessary: he would switch to bronze if it didn’t work out.

A capping ceremony took place late in 1884 with the dedication of the monument itself occurring in early 1885. Aluminum metallurgy was still in its infancy and the design of the cap didn’t function particularly well as a lightning rod, its intended purpose. A violent thunderstorm that summer sent a bolt of lightning into the monument and cracked a stone beneath the pyramidion. That’s when the monument gained its crown of spikes.


Totally Unrelated

I wrote "Confederate Yankees" on August 30, 2011. The Buffalo News wrote "Secessionist hamlet takes stroll down memory lane" on September 6, 2011. It’s an interesting coincidence (and it does appear to be a coincidence). My first scoop?

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