Photos and montage by Flickr user Marshall, Creative Commons
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As slow as molasses.
Photos and montage by Flickr user Marshall, Creative Commons

Swimming In Molasses

Would you have survived the Great Molasses Flood of 1919?

In the Grimm Brothers’ tale, Sweet Porridge, a magic kettle, run amok, drowns a town in porridge. In Tomie dePaola’s Strega Nona, an out-of-control pasta pot inundates a village with noodles. In real life, however, food floods aren’t all that common – which perhaps is why, after they occur, we remember them in capital letters.

There was, for example, the London Beer Flood of 1814, in which an exploding vat of beer at Meux’s Horse Shoe Brewery sent a tsunami of beer through the streets of London. The estimated one million pints of porter toppled walls and houses and drowned eight people. The vat, 21-feet high and 60 feet across, was one of London’s largest; supposedly the brewery’s owners had celebrated its installation by throwing a party for 200 inside it.

And then there was Boston’s Great Molasses Flood. On January 15, 1919, the five-story-high molasses storage tank belonging to the Purity Distilling Company was filled to capacity, its owners reportedly hoping to cash in on the one-year grace period before Prohibition lowered the boom on booze. (Check out National Geographic’s story on molasses and rum.)

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Photo of a panoramic from the 1917 disaster in Boston by Flickr user Boston Public Library, Creative Commons

They never got the chance. Around noon on that fatal day, the bulging tank burst its rivets, projecting two million gallons of molasses through the streets of North Boston. The sticky 15-foot tidal wave, barreling inexorably along at 35 miles per hour, reduced buildings to splinters, threw the Engine 31 firehouse off its foundations, smashed girders on the elevated railway tracks and derailed a train. It also killed 21 people and 12 horses, injured 150, and caused–at a guess–$100 million worth of damage in today’s money. It was one of the worst disasters in Boston’s history.

Molasses, in manageable quantities, is great stuff. The word molasses comes from the Latin mellaceus, which means honey-like, and, like honey, molasses has a complex flavor array–notes like woody, green, sweet, caramel and buttery, according to food scientist Harold McGee.

This tasty mix makes molasses a sought-after ingredient in everything from popcorn balls and gingerbread to licorice, barbecue sauce, baked beans and brown breads. Molasses taffy was a popular treat during the 19th century; children’s parties featured taffy pulls. (Repeated pulling incorporates air bubbles into the taffy, making it lighter and chewier.)

Most famously, though, molasses is sticky. It’s hard to pour because it has a high viscosity – a measure that indicates the resistance of a fluid to flow. Water, which gurgles effortlessly out of the tap, has a viscosity of 1 centipoise or cps. Molasses, which reluctantly oozes, generally measures 5,000 to 10,000 cps. (Ketchup, which legendarily refuses to come out of the bottle, registers a sludgy 50,000 to 70,000 cps.)

Viscosity is affected by temperature: things become slurpier at higher temperatures and stiffer at lower, which is why “slower than molasses in January” means painfully poky.

Caught in a molasses flood, could you swim in the stuff? Probably not, according to an article in Scientific American. The reason has to do with Reynolds number, which helps predict how easily an object or organism can move through a given medium – say an airplane through the air, a swimmer through water, or a horrified Bostonian through a surging sea of molasses.

As swimming goes, the higher the Reynolds number, the better off we are. The Reynolds number for a person in water is about one million. For a person in molasses, on the other hand, the Reynolds number is 130. The luckless Bostonians were trapped in caramelized goo, one researcher writes, like gnats in tree sap.

According to History Today, Boston’s Great Molasses Flood engendered the longest and most expensive lawsuit in Massachusetts’ history. Over 100 separate lawsuits were brought against United States Industrial Alcohol (USIA), the Purity distillery’s parent company. USIA argued vainly that the tank had given way due to sabotage by Italian anarchists. The plaintiffs, backed up by MIT engineering professor Charles Spofford–countered successfully that the steel plates of the tank had been too thin and the rivets too sparse to support the pressure of so much molasses.

The ultimate result was increased concern for public safety, tighter construction regulations, and, at least for a while, more vigilance over big business. Purity’s great molasses tank was never rebuilt.

Over the next decade, demand for molasses plummeted. By the 1920s, Americans had largely thrown over molasses for white cane sugar.

To learn more, see Stephen Puleo’s Dark Tide: The Great Molasses Flood of 1919.