January 15, 1919. North End of Boston. A large tank holding 2,300,000 gallons of molasses bursts, flooding the streets at 35 mph. The sticky wave plows through men, women, children, and horses. The molasses flow is strong and swift enough to knock down buildings and even buckle an elevated railroad, knocking a train off its tracks. The great Boston Molasses Disaster claims 21 lives, not including horses and dogs, and injures 150.

And yet, when rum was dubbed kill-devil, I don't think this is what its critics had in mind.

Rum: A Definition

Rum is a spirit distilled from the fermented juice of sugarcane, sugarcane syrup, sugarcane molasses, or other sugarcane by-products. It's distilled at less than 95% alcohol by volume (190 proof) and bottled at not less than 40% alcohol by volume (80 proof). Note: There are flavored rums bottled at less than 40% alcohol by volume, but I won't be talking much about those.

The legal definition of rum tends to vary from country to country, so establishing a strict definition that applies to all rum from everywhere is impossible. What's consistent, though, is that rum is always based on molasses, sugarcane juice, or other cane by-products.

Most countries that produce rum require the spirit to be aged, so for our purposes, we will define rum as an aged spirit. This means we will not consider Brazilian cachaça to be a form of rum, since it is unaged.

Finally, if instead of the word rum, you see ron or rhum on a label, don't worry. You're merely seeing either the Spanish (ron) or French (rhum) variant of the same word. It's all rum.

Sugarcane and Molasses—Definitions

Normally, when you think of drinking a glass of grass, you're probably thinking of a wheatgrass smoothie, but you're doing the same thing when you belly up and order a daiquri or mojito. Sugarcane, it turns out, is a grass—a member of the same family as corn, wheat, sorghum, and rice.

Rum—most of it, anyway—originates in molasses, a by-product of refined-sugar production. In a way, rum is simply a way to use up industrial waste—the molasses left behind after sugarcane juice was boiled, cooled, and cured.

A Brief History of Sugarcane, Molasses, and Rum

Sugarcane traces its origins to the Indus Valley. Earliest reports of its production date to about 5,000 years ago. Traders carried it into Asia Minor; by the 8th century A.D., Arabs had brought it into Southern Europe and, eventually, Spain. But rum lovers owe some gratitude to Christopher Columbus. It was he who introduced sugarcane to the Caribbean, planting it in Hispaniola (today's home of the Dominican Republic and Haiti) on one of his voyages.

Cane quickly became the staple crop of the Caribbean, providing refined sugar to Europeans and molasses to the New England rum industry. European colonists carried it into much of Central and South America. Cane is now grown in more than 100 countries, supplying not just rum and refined sugar, but also ethanol.

The molasses by-product of sugar production was initially considered waste. It was too heavy to transport from the Caribbean, and at any rate, there was no demand for it. At first, producers simply dumped it into the ocean. At some point (and no one knows exactly where or when), someone seems to have noticed molasses starting to bubble; being familiar with brandy production, sugar producers realized this "waste" was fermenting, and they decided to use it. The molasses still had enough sugar to attract natural yeasts from the air; and the hot, wet environment was perfect for encouraging natural fermentation.

Distillation techniques were refined and well-known by this point, so it was simply natural to take the fermented molasses and distill it down to make a potable beverage.

Growth, Harvest, and Production of Sugarcane and Molasses

Requiring intense heat and a lot of moisture, cane grows only in tropical and subtropical climates. It can grow as high as 19 feet tall and as thick as an inch and a half in diameter. Its thickness can make it difficult to harvest.

Cane is harvested by hand or by machine and then stripped of its leaves. The cane is crushed or mashed to extract its juice. The juice is then boiled, up to three times, to concentrate and crystallize the sugar.

Revenge of the Sugar Beet

Sugarcane, it turns out, is not the only source of refined sugar. During the Napoleonic Wars in the early 1800s, Britain imposed a blockade of France, and this blockade prevented the import of sugarcane from the Caribbean. As a result, French scientists devised a method for the industrial extraction of refined sugar from sugar beets, which—unlike sugarcane—could be grown throughout France and central Europe.

This, however, left the sugarcane industry in Martinique and other French West Indies colonies with a quandary: its chief market for refined sugar had suddenly dried up. The plunge in sugar prices drove many producers into bankruptcy; sugar production declined, and less molasses was available for rum production. Distilleries in those islands turned instead to freshly crushed sugarcane juice. The product that resulted came to be known as "agricultural rum"—or rhum agricole.

How Rum Is Fermented and Distilled

In modern times, most distillers purchase molasses rather than make it themselves. Yeast and water are added to the molasses to create a "wash," which is then allowed to ferment. Some distillers use wild yeasts, but others use specific cultivated strains. We'll look a little later at the role yeast plays in the flavor and character of finished rum.

Fermentation, of course, is the process by which yeasts convert sugars into alcohol. In modern spirits production, this process generally takes place in large metal tanks and is carefully monitored. Fermentation lasts from twenty-four hours to several weeks, depending on the type of rum being produced. We'll look more at these variables a little later.

Depending on the type of rum being produced, distillation can proceed using either a pot still or a column still. Pot stills are more traditional and less efficient—more expensive—than column stills. Generally, heavier rums are produced in pot stills and lighter rums in column stills, although some rums are a blend of pot and column.

Modern pot stills are a variation on the original stills invented by Islamic perfume makers in the Middle Ages.

Factors that Influence Rum Styles

Source of Sugar

The source of sugar used in rum production matters less than you might think. Most modern rum is produced from molasses made in Brazil, so for these rums, the sugar source isn't important, and other factors have greater influence on the style and flavor. In the case of rhum agricole, however, the sugar source carries a certain amount of terroir. Fresh sugarcane juice is prone to oxidation, so it needs to be produced near the distillery, and fermentation needs to begin straight away. Agricole manufacturers say that the use of local sugarcane carries some character from its growing environment into the finished rhum.

Yeast Type

Some rum distillers use wild yeasts, whereas others use specific cultivated strains. Using natural yeast will impart certain characteristics of the local environment into the rum, characteristics that can actually change from batch to batch. To control such variables, some companies use specific cultivated strains that retain the same characteristics from generation to generation. The Los Angeles Times recently wrote about the yeast used by Bacardi, detailing how the Bacardi distillery smuggled its yeast out to Puerto Rico when its original Cuban facilities were nationalized by the Castro government in 1960.

Length of Fermentation

The other variable that yeast introduces is fermentation speed. Some yeast strains convert sugar to alcohol more quickly than others. Bacardi, for example, has bred its yeasts to ferment molasses so quickly that it forms fewer esters and congeners—the chemical substances that create flavor compounds. So one reason Bacardi tastes so light and mild is thanks to its yeast and the speed at which it works.

Type of Still

Another factor that affects rum styles is the type of still used. Pot stills generally produce heavier rums, richer in the congeners and esters that create flavor. Column stills produce lighter rums, stripping out more of the flavor compounds. Column stills are more efficient and therefore less expensive to operate, but it's important to remember this isn't an either-or proposition. Some rums are started in pot stills and redistilled in columns, and some rums are a blend of pot and column.

Type of Barrel

The kind of barrel used for aging rum affects its flavor, too. Some rums are aged in new charred-oak casks; some are aged in used whiskey barrels. Some are aged in sherry casks; some in cognac barrels. All these contribute different flavors to the finished product.

Length of Time in Barrel

This is simple: The longer a rum ages in a barrel, the more flavor compounds it will pick up from the oak.

Strength of Rum at Distillation and Bottling

Most rums on the market are bottled at 80 proof, or 40% alcohol by volume (ABV), but they're distilled to a higher proof—anywhere from 85 to 95% ABV—and then diluted with water to achieve bottling proof. The rums with the richest flavors and bodies are those distilled to a lower proof—say 85% abv—and then diluted to a higher proof—say 43 to 45% abv.

Why is this so? When spirits are distilled to higher and higher proofs, they lose the esters and congeners that build flavor; a rum that comes off the still at 95% ABV will retain fewer flavor compounds than one distilled to 85%. Remember, a spirit distilled to 95% ABV is 95% alcohol and 5% other things. Some part of that 5% is flavor molecules. A spirit distilled to 85% ABV has 15% other things, and therefore more room for flavor molecules.

When you take a rum distilled at 95% ABV and dilute it down to 40%, you need to add a lot of water, which, being water, carries no flavor. So you end up with a lighter tasting rum than if you start with a more flavorful spirit and add less water.

Some flavored rums, incidentally, are bottled at much lower proofs—40 proof, or 20% ABV is common for, for example, coconut or pineapple rum.

Rum Styles

White/Light/Silver: Light bodied, crisp, and subtle in flavor, these rums are highly mixable. They marry very well with fruit flavors, so they're excellent for daiquiris and piña coladas. A common misconception about white rum is that it's unaged. White rum is aged in oak barrels for a short period of time to smooth out the flavors; it's then charcoal filtered to remove color. Bacardi is the best known example of a white rum; other brands include Don Q, Flor de Caña, and Banks Five Island.

Gold/Oro/Ambre: Medium bodied and a little stronger in flavor than light rums, gold rums are aged in oak barrels. Like light rums, they mix well into fruity cocktails. Bacardi, Don Q, and Ron Rico are commonly available brands.

Dark/Black: Full-bodied, with rich caramel flavors, these rums are usually pot-stilled and aged for long periods. Used in tiki preparations such as the Mai Tai, the best of these rums are also sippable on their own, neat or on ice. Mount Gay, Appleton, Gosling's, and Ron Zacapa are common brands.

Rhum agricole: Full-bodied rums, made from sugarcane juice instead of molasses. As with molasses-based rum, agricoles range the color spectrum, from white to gold to dark. Agricoles are often funky and have floral and vegetal aromas and flavors. Brands include Rhum Clement, Rhum J.M., Neisson, and La Favorite.

Other Terms

You may encounter other terms when shopping for rum. Here's a grab-bag glossary of rum words:

Naval rum: A dark, full-bodied rum in the style of that formerly given to members of the British Navy. Normally proofed at 50% abv or higher.

A dark, full-bodied rum in the style of that formerly given to members of the British Navy. Normally proofed at 50% abv or higher. Single barrel: Most rums on the market are blended products. To achieve consistency in taste from release to release, manufacturers blend rums from different barrels to get the balance of flavors right. A single-barrel rum comes from just one barrel, and the rum may taste different from barrel to barrel.

Most rums on the market are blended products. To achieve consistency in taste from release to release, manufacturers blend rums from different barrels to get the balance of flavors right. A single-barrel rum comes from just one barrel, and the rum may taste different from barrel to barrel. Overproof: Refers to rums with an ABV over a standard value, usually 120 proof, or 60% ABV.

Solera: An aging process used in the production of some rums, sherries, and ports, to provide a consistent product from year to year. The solera system involves a pyramid of casks. The top tier is the young stuff, fresh off the still. The bottom layer of casks is mature and ready to bottle. Middle tiers are the middle children. A limited amount is drawn off and bottled from the bottom tier. Rum from the second-lowest layer is moved into the bottom layer, to blend and meld with the older product. Rum then "cascades" from higher layer to lower, each level blending with the older layer below.

Historic and Modern Rum Regions

Caribbean Basin: The birthplace of rum. Styles vary throughout this region, from light and crisp rums to rich, vegetal agricoles.

Mexico: Rum is a relatively new spirit in Mexico; Bacardi has a growing presence there, and you may be able to find an independent brand named Ron Los Valientes.

Central America: The most noteworthy rum producers in this region are Guatemala (Ron Zacapa), Panama (Ron Abuelo), and Nicaragua (Flor de Caña).

South America: Noteworthy producers here include Guyana (El Dorado, which is sometimes also called Demerara rum and called for in tiki recipes) and Venezuela (Pampero). Brazil's cachaça is a sugarcane based spirit that's often called a rum—and is even legally considered such by the United States government—but as it is unaged, we will not consider it a rum for the purposes of this post. I'll have more about cachaça in a future post.

New England: More significant for historic reasons than for modern. New England once had a thriving rum trade, especially in Medford, Massachusetts, and Newport, Rhode Island. Rum is once again distilled in New England, but not in the colonial New England style. (I consider the role that rum and molasses trading played in the history of slavery to be well beyond the scope of this post.)

Africa: The only African rum I'm aware of is Starr African Rum, from the island nation of Mauritius. Distilled from molasses, Starr is a delicious clear, but richly flavored, rum. Cool bottle, too. Certain areas of Africa are perfect for growing sugarcane, so Africa may become a region to watch for future rum production and an evolution of rum styles.

Important Rum Houses

Angostura—Trinidad. The same house that makes the famous bitters also distills rum.

Appleton—Jamaica.

Bacardi—Puerto Rico/Mexico. Originally Cuba. Light, crisp style, good for mixing.

Barbancourt—Haiti. Rhum agricole.

Brugal—Dominican Republic.

Clement—Martinique. Rhum agricole.

Cruzan—US Virgin Islands.

Demerara / El Dorado—Guyana. Dark, rich rums aged in bourbon barrels.

Don Q—Puerto Rico. Light, gold, and dark rums in the Cuban/PR style, similar to Bacardi, but less expensive and, in my opinion, more flavorful.

Gosling's Black Seal—Bermuda.

Havana Club—Cuba. (Bacardi also makes and markets a rum by this name, but only in the United States. The Bacardi version is made in Puerto Rico.)

Mount Gay—Barbados.

Myers—Jamaica.

Zacapa—Guatemala.

Rum Cocktails You Should Know

Well, that's all fine and good, Professor Barman, but we just want to drink. What do you have for us?

SE: Drinks has a lot of rum recipes you could try, but here are my personal favorites:

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