The Rum Distillation Process

How to Distill Rum: The Basics

Rum distillation is a combination of science and art. At Montanya Distillers, we ferment just four ingredients: raw unrefined sugar cane, unrefined molasses, yeast and Colorado mountain water.

After six to seven days in fermentation, the resulting “wash” is transferred to our 400-liter stills, where the liquid is heated to separate the alcohols. The still converts that alcohol to vapor form and then returns it to liquid through a condenser. The purest part (the hearts and part of the transitions) is then aged in American White Oak barrels with a #3 or #4 char.

Sometimes people are surprised when they visit the distillery. They see only two stills upstairs from the tasting room and a couple of barrels. It’s not a display, however. Batch distilling and efficiency allow us to meet all of our production needs with the two 100-gallon stills running frequently, and we age the rum at our second facility—a warehouse, bottling line and rack house.

The fermentation tanks at Montanya Distillers.

The fermentation tanks at Montanya Distillers.

Our Rum Stills

We like tradition at Montanya Distillers, so we use copper stills from Portugal. Everything we make starts in these stills—whether it’s rum for the tasting room and bar, or rum that we ship around the US or to Europe. We’ve even named them, and you can learn more about them here. Trust us, they have personalities of their own!

Distilling Rum By the Numbers

At Montanya Distillers, each batch of rum requires:

  • About 400 pounds of raw, unrefined cane sugar

  • 50 to 60 pounds of unrefined, black strap molasses

  • 150 gallons of water

  • 6 to 7 days of fermentation

Each batch yields:

  • A wash that’s about 16 percent alcohol by volume

  • 13 - 15 gallons of un-aged rum (called hearts) per still per run

And each barrel:

  • Fits 53 gallons of rum, which we fill to 50

  • Weighs 550 to 600 pounds

The still heats the wash to separate the alcohol from the rest of the liquid.

The still heats the wash to separate the alcohol from the rest of the liquid.

The Distillation Process: Specifics

if you tour the distillery, you’ll hear a few terms getting tossed around: heads, hearts and tails. We’re not talking body parts. These are industry terms meant to refer to the different parts of the alcohol run produced through distilling.

Once the wash has been transferred from the fermentation tanks to the stills, the distiller brings it up to a slow heat to vaporize the ethanol. That vapor then goes through a condenser, where the the alcohol is turned back into a liquid and comes out of the still as rum. Only the lightest and purest vapors escape the still.

Alcohol coming off of the still.

Alcohol coming off of the still.

As the temperature increases, different forms of alcohol are produced. We want only the purest alcohol and flavors to make our rum, so we make “cuts” between the different types of alcohol. It’s really just the point at which the alcohol transitions from one phase to the next.

For example, early in the process, lower temperatures produce alcohols like volatile alcohols, ketones and esters. These alcohols that we don’t want are referred to as the “heads.” As the process continues, we reach purer ethanol. It has all the concentrated flavors that the yeast created during fermentation, and it’s the part of the rum that we want to barrel and age. This is called the “hearts.”

Eventually, the boiling point in the still gets closer to the boiling point of water. The percentage of alcohol goes down and the water content goes up. This is what we call the “tails.” We don’t put the tails in the barrels, but they do possess some flavors we like. They go back into the stills to be redistilled several more times to extract their best flavors (the transition between the hearts and tails is often called the Queen’s Share in rum production, since so many great flavors live in this transition.)

Montanya Distillers ages its rum in barrels that previously held Laws Colorado Whiskey.

Montanya Distillers ages its rum in barrels that previously held Laws Colorado Whiskey.

Aging Rum

Many factors influence the way a rum ages, like the the length of time it ages, the type of barrel, the char on the barrel, and even the altitude, humidity and temperature in the rack house. We use whiskey barrels to add subtle additional character, and each rum has a distinct aging process to help cultivate its flavors.


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