Edwards Engineering Corporation
a Division of Applied Sugar Technology
1773 Westborough Drive
Katy, Texas 77449 U. S. A.
Tel.: +1(713) 849 - 6825 Fax.: +1(713) 849 - 5638
Internet: www.EdwardsEngrg.com E. Mail: info@EdwardsEngrg.com
How to Make Rum
By Tristan Stephenson
Rum is one of the easiest spirits to make, since the laws and regulations that
surround it are slack, to say the least. The only real ‘hard and fast’ rule when it
comes to rum is that it has to be made from sugarcane.
Sugarcane is a type of grass; when you press it, the resulting juice has a sugar
content of between 15-20 brix (15-20% sugar). It’s not often that you see crates
of raw sugar cane in your local supermarket, but sugar cane products are readily
available in the form of crystallized sugar. Different sugars will make subtle
changes to the flavor of a rum; each type of sugar is unique depending on its
production and origin.
You can also make rum from sugar cane honey (the juice of the cane boiled
down and concentrated), or molasses.
Fermentation
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Molasses is the raw material used to make the vast majority of the world’s
rums. Quite simply, molasses is the bi-product of the sugar refining process.
Once all easily obtainable sugar has been extracted from the juice of sugar cane,
the leftover sticky black substance is known as ‘black-strap’ or molasses.
Surprisingly it can be as rich as 50 brix (50% sugar), though usually it is around
20-30 brix.
These sugars are perfect for fermenting and the other compounds within the
molasses provide adequate nutrients for the yeast to thrive.
Fermentation can last anything from 50 hours, right up to 2 weeks for rum. The
hot Caribbean/Central American climate, that most rums are produced in, lends
itself well to a speedy and efficient ferment, thriving in 25-30°C. Molasses needs
first to be diluted with around four parts water to every single part of molasses
(though every producer will differ slightly). The sugar level of undiluted molasses
would be uninhabitable for yeast.
First, warm you molasses up in a sink full of hot water; this will make it less
viscous. Pour the molasses into a fermenting bin and add hot water equal to four
times the volume of molasses. The water will need to be hot in order to dilute the
molasses sufficiently. Let it cool. When the mixture reaches around 35°C it’s time
to add the yeast. Any wine making or, even better, champagne yeast will be up to
the challenge. Hydrate well before adding it, and then give everything a jolly
good stir to aerate.
Molasses
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Weird Molasses bubbles captured while stirring
At this stage it is advisable to use a hydrometer to measure the specific gravity
(or relative density) of the unfermented wort. The hydrometer will float at different
levels according to the liquids density and its potential alcohol content. A reading
of around 1.050 to 1.080 would be a desirable, as it indicates a potential to
create 6-10% abv. Once fully fermented another reading can be taken, deducting
that number from the original SG will tell you the final abv of the wash, with the
help of this chart. http://www.home-winemaking.com/images/hydrometer.jpg
When fermentation is complete the liquid is a bit like a heavy porter, or rich
liquorice wine, retaining little of its original sweetness. The sugar has been eaten
up by the yeast and converted into alcohol.
This molasses wine is now ready to be distilled.
Distillation
Most modern rums derive much of their flavor from the ageing process. Often
we associate the natural influence of American oak as the flavor of distilled sugar
cane, but a lot of the time we are simply tasting the magical influence oak has on
a relatively neutral spirit. There are of course exceptions (Wray & Nephew
springs to mind), but many of our favorite brands retain little of their distillate
character when it eventually comes to bottling.
Rum that is made in a column still usually has most, if not all, of is
characteristics removed. It is essentially purified, much like a vodka. In fact many
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new make (un-aged) rums could be legally sold as vodkas if the producer was
inclined to do so.
Rum that is pot distilled (in much the same way as a whisky) tends to retain
more of the flavors and aromas from the molasses or cane that it is made from.
This artisan method of production is far less efficient than a column still, but it
does often result in a more naturally characterful spirit. Retaining rich, resinous
sugar flavors and usually a fair amount of liquorice too.
The strength of the distillate extracted from a pot still will depend on the shape
and height of the still. The longer the neck on a still, the purer and lighter the
spirit will be, this is because a long neck encourages reflux to occur. Reflux is a
process of evaporation and condensation of spirit and water vapor that takes
place continuously within most pot stills. As the fermented wash rises up the
neck, the distiller controls the temperature at the head. A steady decrease in
temperature from bottom to top encourages only light alcohols to make their way
up and over the ‘goose’s neck’. The longer the neck, the greater the chance that
impure low alcohols and water will never make it over and in to the condenser.
With this in mind, a pot still with a long neck can produce a spirit of anything up
to 40%abv in the first run. This stuff won’t be all that drinkable mind you,
containing many of the soluble impurities from the wash as well as lighter
alcohols like methanol and acetone. Now, the second distillation in pot still is
where it’s at, further purifying the spirit and drawing off liquid somewhere in the
region of 80% abv.
At this level the resulting liquid (when cut with water to 40% abv) doesn’t smell
particularly nice. Plenty of harsh liquorice notes and none of the sweet, buttery
candy-floss tones that we would commonly associate with spirit derived from
sugary nectar. But the process is not finished just yet, oh no no no!
The next part involves patience (and an oak barrel*).
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Ageing
The Cask
Coincidentally this barrel has my name on it!
The spirit requires ageing.
As I already mentioned, the vast majority of the rums available today go
through an ageing process, sometimes only for a matter of days. The reason that
producers do this is to positively alter the flavor of the distillate. I often liken oak
barrels to inside-out tea bags. The wood contains flavors (cellulose, hemicellulose, tannins and lignins) that will interact with the spirit and, aided by a
degree of oxidization, have a massive impact on the aroma and taste of the
liquid.
The surface area of a 5 liter cask is around 2000 cm² (2.5ml/cm²),
comparatively an average industrial oak cask would have a volume of 200 liter
and a surface area of 20,000 cm² (10ml/cm²). A barrel forty times the size has
four times the liquid volume to surface area ratio.
In a tiny 5 liter cask, with a low surface area to volume ratio, the effect is
noticeable in less than a day.
Below is a picture of rum extracted from a 5 liter cask after only a month
ageing. The rum went in to the barrel crystal clear, but during its time in there it
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has picked up color as well as soluble and insoluble compounds. An alcometer
tells us that the spirit has an abv of 43%.
Rum aged for 1 month in a 5 liter cask
A few things to take note of:
1. It’s cloudy. It seems that some of the compounds taken from the oak are
insoluble in water/alcohol. You might suspect that the cloudiness is a result
of fusel oils present within the distillate itself, but I can assure you that the
spirit was crystal clear before entering the cask.
2. It has a strange green tinge to it (we’re all thinking urine, I know), rather
than the golden color that we would normally associate with rum.
On a plus side, however, I can vouch for both its taste and smell. The barrel
has performed a miracle act, converting some very stubborn odors into buttery,
caramel, chocolate softness. The length of finish was once a sickening liquorice
twang, now it is a soft, mouth-coating warmth, with just a touch of resinous sugar
sweetness. It’s not the best rum in the world, but it’s flavorsome, interesting and,
dare I say it, balanced.
So, how to get rid of the cloudiness?
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Filtration
Let’s start with a simple mechanical filtration, a paper coffee filter should do.
The Filter
As you can see, the paper filter has removed much of the larger debris,
leaving a residue of brown… stuff… tiny bits of oak I’m assuming. But the spirit is
still cloudy. Time for some more aggressive techniques, charcoal filtration should
help.
Many of the white rums that we consume are in fact aged products that have
been filtered in order to remove the color. In many cases this is stated on the
label: Havana Club Anejo Blanco, “aged white”. As with any other aged rum, this
is done to positively influence the flavor and aroma of the product, softening
some of the more aggressive distillery characteristics. These white rums, which
are stripped of their color, are almost always filtered through activated carbon.
Activated charcoal is of course quite easy to get hold of, it’s the stuff inside any
common water filter cartridge.
I’m going to give my filtration an even better chance of removing the
cloudiness by first cooling the spirit right down in a freezer. In the spirits industry
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this is called ‘chill filtering’. It works on the basis that many of the fatty acids,
esters and proteins present within spirits are insoluble at lower temperatures. By
chilling the liquid down the filtration process is more likely to be effective. You
might have seen certain whiskies advertising themselves as ‘non-chill filtered’.
This is because many whisky aficionados believe that the removal of these
insoluble compounds is actually detrimental to the taste and aroma of the final
product. A non-chill filtered whisky can often be spotted by the addition of water,
as many of the compounds that would be removed by the process are also
insoluble in lower alcohol solutions. Chill filtering is usually performed at around
0ºC.
Chill Filtering
And the result? It’s still a bit cloudy…
Final Clarity of rum
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So the final product is a liquid that has lost much of its color through the
filtration process, and certainly a degree of its cloudiness, but not all of it. I would
wager that more filtering, perhaps through a larger filter, would remove all of the
haze and probably most of the color. Or perhaps a laboratory grade filter? Or
maybe chilling down the charcoal?
Maybe I’ll have to think about it while sipping on a nice ‘Dark and Stormy
Clouds’!
* The “oak barrel” aging is a stumbling block that many home distillers / fermenters come across.
They are ridiculously hard to find, when you DO find them (if they’re in reasonably good condition)
they’re prohibitively expensive for the average hobbyist…. and if you’re trying to make your own
barrel…. well, it’s probably easier to just scour around and try to find a decent used one and just
cough up the cash.
One method that I’ve used in the past for both rum and bourbon aging was to use a stainless
steel container and “line” it with charred white oak.
You’ll need a container that can be sealed pretty much air tight, with a wide enough opening that
you can get both hands/arms inside to place (and then remove if necessary) the pieces of wood.
It’s also nice if there’s some sort of spout at the bottom to make straining/filtering easier.
Go to a lumberyard (not Lowe’s or Home Depot)… smaller private yards are more likely to have a
larger variety of wood species available, or should be able to direct you as to where to get the
relatively small quantities you’ll need.
You need to get yourself WHITE OAK (there’s also red oak, which you don’t want). Cut it into
pieces long enough to stand up in your stainless container. Make enough of them to sort of “line”
the inside of your container… but you don’t have to worry about actually attaching it.
Once you have your pieces of white oak cut, now is the fun part…. go outside and burn them with
a torch. Don’t burn them completely to ash and cinders – you want to get them good and charred
on the surface of all sides. After they’ve cooled off enough that you can handle them, take a stiff
brush to them and just knock off any loose particles.
Now insert these pieces of charred white oak into your container, fill the container to the top with
your distillate, and close/seal the lid and let the container sit for a week/month/year… if your
container has a spout on it (like a hose spicket) you can take small samples throughout the aging
process if you like.
With about 8-12 mo aging, I’ve found this to produce a nice deep amber color, as well as a really
smooth yet bold flavor, somewhere between a “gold” and “dark”.
Good luck!
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