How to make rum
Hendre Barnard

By Hendre’ Barnard, Training and Marketing Manager
Distillique Beverage (Pty) Ltd.

Published : 28-07-2020

DISCLAIMER: Distillique does not believe in providing and selling recipes, as this goes against the Craft of producing your own products. The recipes we share have been sourced from clients and other sources, and as such, Distillique takes no responsibility and makes no guarantees regarding the quality, accuracy, or safety of these recipes. Recipes are used at own risk, and are for the purpose of experimentation, inspiration, and guidance.

Why make Rum?

As the Second Alcohol Ban of the COVID-19 crises grips South Africans, more and more individuals are turning to producing their own alcohol. Having tired of Sugar Washes, Fruit becoming too expensive and not many mastering the intricacies of Starch Conversion required to make proper Whisky, Moonshine or Bourbon, the fall-back position for many has become Rum.

In theory it sounds easy – take molasses which contains sugar, add water, add yeast, let it ferment, and then distill it. Watch enough Rum Distillery Marketing videos on YouTube and you would certainly believe it is that easy. But few people realise the intricacies that is actually involved in making a true (and good) Rum. 

In a previous Article: The Components of a True Rum, we explored this already, and a lot of what will be in this Rum Recipe will draw inspiration from that article, but without getting into the true intricacies of Rum making. If you are truly passionate about Rum and want to learn more about making the real thing, from scratch, using your own inspiration and choices, we highly recommend you enrol in our W5 – High Brix Raw Material Spirit Online Training Course, otherwise known as our Light, Gold, Dark and Spiced Rum Course.

PLEASE NOTE: If you were looking for a nice, easy, step-by-step Recipe to make Rum, you will be disappointed. Making proper Rum is not simple or easy, and there are so many options to consider that writing a simple recipe like that is impossible. This article’s goal is to help you navigate these options and choices.

What Molasses do I use for Rum?

According to International Convention, South African Liquor Law, and Tradition, a Rum is produced from one of three raw materials:

  • Molasses
  • Sugar Cane Juice
  • Sugar Cane Syrup

Of these three, only Molasses is readily available to the Home or Hobby Distiller, although one of our Strategic Partners, Cane Juice Co. , does provide fresh or frozen Cane Juice in various volumes in Cape Town. Using Cane Juice to produce Rum results in what is know as Rhum Agricole or Agricultural Rum, also referred too as French Style Rum. This would be similar to the Rums of Seychelles and Mauritius. 

Sugar Cane Syrup is sometime misunderstood, with some distillers thinking they can use Dextrose, Liquid Glucose, Invert Sugar, or just dissolve Granulated Sugar in water and use that. The law is however very clear and defines Sugar Syrup as a by-product of the processing of Sugar Cane Juice. Specifically, it refers too the concentrated Sugar Juice solution after the first Evaporation of excess water from the Sugar Cane Juice.

But enough about the other options. What Molasses do I use?

As with most things in life, not all Molasses are created equal. You get different Grades of Molasses, and they are called by different names depending on the company and country in question. Let’s take one supplier in South Africa as an example.

The Huletts sugar company supplies Treacle 1 Molasses, Treacle 3 Molasses and Blackstrap Molasses. Each of these has the same Brix content, i.e. 80% Brix. 

Now, for those of you who have not yet done our C1 – Introduction to Distilling Course, Brix is a scale of Sugar Measurement, similar to the SG Scale, Plato Scale or Balling Scale. But when it comes to fermentations, what these scales are measuring is not always sugar. In a Fruit Juice, Grain Wash or Sugar Water Fermentation, yes, it is mostly measuring Sugar. But not when dealing with Molasses.

With Molasses we are dealing with 2 different types of Brix Solids, Fermentable and Non-Fermentable.

Fermentable Brix Solids covers Inverted Sugars (Glucose and Fructose) which is easily and directly fermentable, and Sucrose (a disaccharide molecule consisting out of one Glucose and one Fructose molecule), the latter of which is relatively easily fermentable after Hydrolysis by the Yeast.

Non-Fermentable Brix Solids include Caramelized Sugar, ash, minerals, etc. which dissolves in water, but as the name implies, is not fermentable. It therefore stays dissolved, increases the density of the liquid, and affects your SG Hydrometer (as well as your Refractometer). This means you will always get a Brix or SG reading because of the increased density caused by their presence, whether the fermentation is done or not – but let us not skip ahead.

The issue comes in that the ratio of Fermentable Brix Solids vs Non-Fermentable Brix Solids changes between the different Grades of Molasses – the more pure the Molasses, the more Fermentable Brix Solids and the less Non-Fermentable Brix Solids. 

Treacle 1 for instance (normally sold in the shops for baking and human consumption), has a Total Brix of 80%, and a Fermentable Brix of 79%, hence it is almost completely fermentable, and your SG will drop to relatively close to 1.000 at the end of Fermentation, Brix reading close to 0% at the end.

Treacle 3 (normally used in the flavouring industries), has a Total Brix of 80%, and a Fermentable Brix of 50 to 60%, so if that is used in the fermentation, the SG level will only drop by 50 to 60%.

Blackstrap Molasses (normally used in animal feed), has a Total Brix of 80%, and a Fermentable Brix of only 40%, so if that is used in the fermentation, the SG level will only drop by 40%.

Here is a quick guide:

 Treacle 1Treacle 3Black Strap
Total Brix80%80%80%
Fermentable Brix79%60%40%
Non-Fermentable Brix1%20%40%

PLEASE NOTE: These values are indicative. The actual percentages vary from batch to batch. That is why you should always buy from a supplier (like Distillique) that can give you a Lab Analysis Sheet per batch, so that you know what you are dealing with and make your calculations accordingly.

How much Molasses do I use to make Rum?

PLEASE NOTE: These Recipes are meant for Home and Hobby Distillers, and therefore assumes that Sugar will be added to get maximum yield. This is not Legal for Commercial Distillers.

Now, I’m not going to go too much into the Calculations, Alcohol and Brix Tolerances of different Yeast Strains, etc. If you want to know how to work this out for yourself, you can join our C1 – Introduction to Distilling Class, our W5 – Light, Gold, Dark and Spiced Rum Class, and reference our Article on Handy Sugar Calculations.

For now, let it suffice to say that the following Table lists the amount of each type of Molasses to use, with sugar added to get maximum yield, for 5 different types of yeast, for a 20lt Fermentation. You will either need to multiple or divide for your fermentation size. Unlike Yeast, this calculation is linear.

Molasses GradeSugar SourceChampagne Yeast   (19% ABV)Distillers Yeast    (16% ABV)Wine Yeast (15% ABV)Beer Yeast (10% ABV)Bread Yeast (8% ABV)
Treacle 1Molasses8.6 kg7.2 kg6.8 kg4.5 kg3.6 kg
Sugar0 kg0 kg0 kg0 kg0 kg
Treacle 3Molasses5.9 kg4.9 kg4.6 kg3.1 kg2.5 kg
Sugar3.2 kg2.7 kg2.6 kg1.7 kg1.4 kg
BlackstrapMolasses3.7 kg3.1 kg2.9 kg1.9 kg1.6 kg
Sugar5.0 kg4.2 kg3.9 kg2.6 kg2.1 kg

PLEASE NOTE: For the sake of deviation in Batches, I assumed Treacle 1 to contain 75% fermentable sugars, Treacle 3 to contain 55% fermentable sugars, and Blackstrap to contain 35% fermentable sugars. In standard batches, based on the figures given earlier, these dosages will be too much sugar.

ALSO: Assumptions made in terms of the Total Brix Tolerance of the different Yeast Strains. These assumptions were 45% for Champagne Yeast, 42% for Distillers Yeast, 35% for Wine Yeast, 30% for Beer Yeast and 28% for Bread Yeast.

What Water do I add for a Rum Fermentation?

After you have weighed out your Molasses and Sugar, take about 12lt of warm water per 20lt fermentation. Warm water will allow the molasses and sugar to dissolve easier. This water should be low in chlorine (absent if possible) and VERY low in mineral content, especially if using Feed Molasses (Blackstrap), which already contains a lot of minerals of its own. This gets tricky on agricultural properties using borehole water. 

Stir vigorously until all the Molasses and Sugar is dissolved. A paint mixer attachment on a drill becomes handy here. This also aerates the fermentation, which is very important for Yeast Procreation. Then top up to the 20lt mark (or whatever fermentation volume you are making) with more water.

What pH should my Rum Fermentation be?

Let yourself be guided by the pH requirements of your yeast. One thing to consider though, especially if you added sugar, but even with the high sucrose content of the Molasses – due to Hydrolises of the Sucrose Molecules (as they get broken apart into Glucose and Fructose) the pH will drop quickly and heavily. It is therefore not a bad idea to aim slightly higher with your starting pH.

Most of the Yeasts used with Rum Fermentations are either Wine or Distiller’s Yeasts, and they tend to prefer pH ranges between 4.5 and 5.5 at the highest. You can aim for these pH ranges as your starting pH when using Treacle 1, but with Treacle 3, aim 0.5 points higher, and with Blackstrap, aim 1.0 point higher, due to the added sugar amounts.

pH can be adjusted upwards using Potassium Carbonate. Some Home Distillers or Hobby Distillers use Sodium Bicarbonate, but the problem with that is that the Sodium Bicarbonate has a much lower pH than Potassium Carbonate, so you end up using a lot more to get the same pH change, and it therefore becomes much more expensive. Also, Sodium Bicarbonate has a lag phase in affecting the pH, while Potassium Carbonate does not, hence you can be more accurate with Potassium Carbonate.

You will obviously need either pH Strips or a Digital pH Meter in order to measure your pH adjustments.

Do I need to add Nutrients to my Rum Fermentation?

YES !!!

A lot of people are under the mistaken impression that Molasses, especially Blackstrap Molasses, contains sufficient nutrients in order to not add additional nutrients. This is both true and false. While Molasses does contain Vitamin B and certain critical Mineral Salts, it lacks Nitrogen in particular, so Yeast Nutrients should be added – an equal amount as the amount of yeast. If you do not have Yeast Nutrients, you should at the very least add DAP (Di-Ammonium Phosphate) to add Nitrogen to the Fermentation. The same ratio applies.

For more information on Yeast Nutrients, refer to our Article on The Importance of Yeast Nutrients.

What Yeast do I use in my Rum Fermentation?

Now, and I cannot stress this enough, you do NOT just choose Yeast based on what’s available or how much alcohol can it give me. Yeast should ALWAYS be chosen on the basis of what flavours and aromas does it create. What does the Yeast contribute to the Fermentation?

Our Article on Selecting the Right Yeast Strain will explain just some of the factors to consider here, but Flavour and Aroma will always be the most important factors. Normally with Molasses Fermentations we prefer a Red Wine Strain, although certain White Wine Strains also contribute nice profiles – a firm favourite is Rhone 4600 – although you can also consider VIN13NT116, or WE372. Esters are always important in Rum, so Alchemy I would also be a suitable choice, as would the Tobacco Flavours we get from NT202. Then there is also MTR01 – a yeast specifically formulated for “Quick and Dirty Rum Fermentations, with high tolerances, especially towards Temperature, but very little flavour benefit.

The amount of Yeast varies from strain to strain and can be as little as 30g per 100lt to as high as 75g per 100lt, but this is only true for larger fermentations. Smaller fermentations – less than 100lt – you add 1g per litre, so 20 grams in a 20 litre fermentation. 

If you cannot get hold of proper yeast, and you are stuck with bread yeast, you will need to overdose – 2 grams per litre, or 40 grams in a 20 litre fermentation, but you keep the yeast nutrients the same.

At what Temperature do I keep my Fermentation?

Normally the rule with Fermentations, especially Fruit Fermentations, is the colder the better. It takes longer, but the yeast is happier, and you get more of that desirable fruity flavours and aromas.  The same is however not true with Rum. Rum likes “Quick and Dirty” Fermentations as this leads to more Ester formation – reference our Article on The Components of a True Rum for more information.

Keep your fermentation at 30 to 34 degrees Celsius using an Aquarium Heater, or some other Heat Source.

What do I do about the Foam?

Rum fermentations have a tendency to Foam heavily, both during Fermentation and Distillation. One technique is to leave additional headspace during the fermentation process – at least 15 to 20%. So, if you are making a 20lt fermentation, use a 25lt Fermentation Bucket.

The other technique is to use Anti-Foaming Agent. This will stop foam from forming in the first place.

What do I do when my Fermentation is finished Fermenting?

When your Fermentation is done, do not stress if you still have an SG reading. As stated before, you will always have residual Unfermentable Brix Solids in the Fermentation, even when completed.

Now, before you distill, it is a good idea to clarify your fermentation. Not necessarily to get it “clear” – that is impossible, it will remain black – but to reduce the amount of non-fermentable Brix Solids that enter into the boiler. These compounds will lead to increased foaming during distillation (so much so that it can push through your entire still and contaminate your condenser or spew out the other side) or it can burn or scorch inside the boiler, leading to burnt flavours and aromas, or what we call “Yeast bite” or “Yeast burn”. 

You can clarify the Fermentation using Chitosan and KieselsolBentonite, or just by Cold-Crashing. Cold-Crashing is where you put the fermentation in a cold spot (your garage at night) or in a fridge, and the cold causes the suspended solids to settle out to the bottom within 24 to 48 hours. You then siphon the fermentation off above the sediment so as not to get any of it in the fermentation.

How do I Distill my Rum?

The ideal method of Distilling Rum depends on the style of Rum you wish to produce, but also the type of Molasses you used in the fermentation. 

If you have done training with us, you would already be aware that the percentage you distill at determines your flavour profile. That is why high percentage distillate is never good unless you are doing Vodka or a Sugar Wash.

If your goal is to make a Heavy, Dark, Potent Jamaican Style Rum, you are looking for low percentage distillate, so you retain a lot of flavor, so you distill in a Potstill or Alembic Still. If your goal is a Barrel Aged Gold or Oro Rum where you can pick up more wood and sherry flavors form the wood chips or barrel, you are looking for less Molasses flavor, so you would distill at a higher percentage, ideally using a Reflux Still. 

BUT – the lower the quality of the molasses, the higher the taste profile, so if you used Blackstrap Molasses, the Pot Still distillate will be TOO overwhelming. Then you can even maintain a heavy taste profile with a Reflux Still, while Treacle 1 Molasses with Reflux can still lose almost all of its flavor, so you can distill it at a lower percentage, and it will still not have a “Heavy” flavor profile.

One thing is however very important when distilling Rum – Low and Slow. Not only to avoid excessive foaming, but also to get a nice clean separation of flavors and aromas through Fractional Distillation. You can read more about this in our Article on The Effect of Boiling Rate on Fractions.

After distillation, the best thing to do with your Rum is put it on Wood, ideally the traditional French Oak, 8 years old, 4 years used for Red Wine and 4 years on Sherry, so that all that flavor and color can pull into the Rum. This can be accomplished either with Oak Chips, or small Barrels. And do not forget to use Spirit Caramel to make your Dark Rum.

What is Multi-Generational Rum and Dunder?

After you have distilled your Rum, you will find in your boiler the normal stillage. The left-over spent fermentation which may or may not still contain some ethanol (depending on whether or not you stripped off the tails of your fermentation). This is what you will use in your Multi-Generational Rums, and what is referred to as Dunder.

Our article on The Components of a True Rum explores the mysteries of Dunder in detail, and specifically the greatly misunderstood difference between Dunder and Muck. We also handle this in-depth in our W5 – High Brix Raw Material Spirit Online Training Course. For the sake of brevity though, to make a Multi-Generational Rum, and increase the flavour profile of your next batch, you do not discard all of the stillage left in the boiler, but you keep about 8 litres of it (per 20lt fermentation).  

In your next fermentation, you then substitute 8lt of warm water, for 8lt of warm stillage (Dunder). This will greatly increase the flavour profile of the next batch, and the next batch, and the next batch.

BUT … watch out.

If you used Blackstrap Molasses, the residual solids might get too much in following generations and kill the yeast due to osmotic stress (Brix Tolerance). To avoid this, test the SG of the Dunder before deciding how much to add.

If you left a lot of alcohol behind, you may waste sugar in the next batch as the Yeast will die when it reaches its alcohol tolerance faster. To avoid this, strip the tails off, keep separate, and add to the fermentation when it is done, prior to distilling it.

We hope this will help you in making better and more successful Rum Fermentations.