The world of dunder in rum is explored here by Ben who explains the phenomenon behind the funk and why a love of it contributed to the creation of Dunderhead Rum.




  1. A dunce; blockhead; a stupid person
  2. A rum connoisseur, one who enjoys funky, fruity flavours

So this one’s a re-launch rather than a brand new product, but it’s probably worth a story or two to explain where the idea came from, why this particular rum (in a sea of hundreds) is worth your attention, and a place on your bar.

We launched Dunderhead rum back in May 2020* and it’s fair to say it’s been a pretty epic success. So much so that we’ve gone the extra mile and given it a brand-new look for 2023. Despite the snazzy new loo, an evolution of the original design brief [and I promise I’m not making this up] of ‘Scary Pirate Steampunk Skellington Tattoo’, the recipe, price-point and brand’s overarching raison-d’etre remain unchanged. 

A bottle of Dunderhead Rum

The new look Dunderhead

Putting the dunder in Dunderhead Rum

Dunder is one of the fundamental (and one of the most often mischaracterised) ingredients/techniques associated with rum-making (with Jamaican rums in particular) and while I won’t go into huge masses of detail about the technical aspects of its production (this article is exceptional if you have the time) I can summarise it thusly:

Dunder is:

1. A vatted collection of  ‘setback’ from rum distillation (in layman’s terms, the rich liquid stuff that’s left in the still after you’ve distilled off all the booze).

2. Packed full of concentrated flavour, made all the more complex because (deprived of the stabilising influence of alcohol) it undergoes bacterial as well as yeast-based fermentation. 

3. A bubbling broiling mass of black gloop which (on its own) is overpoweringly intense, but which through measured addition gives us ‘ester-y’ notes of pineapple, banana, and strawberry, and through slightly less measured addition gives the ‘funk’ in more powerful rums.

4. …to rum, what peat is to whisky. Massive oversimplification, but it can be treated like a ‘seasoning’ which works wonders in accentuating the natural flavour of the base spirit.

Dunder is not:

1. Muck. Muckpits are (historically) the big old pit outside the distillery (and more commonly inside in a vat nowadays to avoid the rumours about dead goats falling into them**). The solids which settle out of the dunder over time go in the muck pit, along with spent lees from the stills and various other flavoursome*** waste products such as cane shreddings. Muck is also added back into the still in measured quantity to add yet more flavour.


Dunder = fruity, ester-rich flavour

You’re going to have to trust me when I say that the above is a huge simplification of the fiendishly complex organic chemistry that goes on in cultivating, and subsequently releasing these prized ester compounds from the various products and byproducts of distillation.

Broad strokes though, we can take from this that dunder = fruity, ester-rich flavour.

When we put together the liquid, we started with a base blend of good quality, but (in relative terms) clean and simple Caribbean rum. We then seasoned that base with an incredibly high-ester single-distillery make, to add those fruity and ester-rich notes that us Dunderheads love. 

For those of you who are more tuned in to the whisky blending side of things, let me give you some facts and figures to help explain the reason that we were able to do this (start with a comparatively straight-forward base yet end up with a thoroughly flavoursome rum)…

A typically ‘peaty’ whisky such as Ardbeg 10 Year Old has a finished distillate Phenol level of about 55ppm (parts per million). Bruichladdich Octomore’s annual releases regularly hit levels of 200ppm+, with the 8.3 release having tipped the scales at a super-extreme 308ppm.

By contrast, a typically ‘fruity/funky’ rum may have ester levels ranging from 30 to 100 ppm, but the extreme end of the scale for esters is more stratospheric. There is a legal export limit (from Jamaica at least) of 1600ppm meaning that this is as high as production goes. Practically, the limits are significantly higher, as they’re dedicated only by the quantity (and funkiness) of dunder added to the wash before it’s distilled.

The delta between the finished product and the ‘ultra-flavour’ variant in whisky therefore is approximately 4:1, whereas in rum it can be upwards of 30:1.

Using ‘ester levels’ as a proxy for flavour is of course an extremely one-dimensional approach to categorising and describing a rum’s flavour, arguably more so than ppm in whisky, it’d be like trying to describe a steak by reference to how salty it is. 

Dunderhead Rum

A delicious steak. But don’t lose focus too much. We’re talking about rum. Juicy, medium-rare rum…

The delights of Dunderhead

All this (to pull it back to the product and flavour and away from delicious delicious steak) means that we are able to take the smoothness and mixability of the base rum, and give it a judicious measure of the ester-y fruity top notes that we want, but without too much getting in the way in the mid-palate. 

I’ve been doing some experimenting with this liquid over the last couple of years [Yes. That’s it. Experiments. Let’s go with that], and can confirm that in nearly every rum cocktail which follows the ‘sour/tiki’ path (think Daiquiris, Mai Tais, Piña Coladas**** and the like) the mixability of this product is absolutely superb. The fruity high notes have an ability to lift themselves above the citrus, and make themselves known in an entirely welcome manner. I’ve had bad experiences with super-high ester rums used in cocktails like this by well-meaning bartenders (Wray&Nephew overproof Snackquiris are not okay), and it’s a fine line to tread. I’m comfortable that we’re on the right side of it with this one.

It also pairs extremely well with coke (duh – prerequisite), the fruity and ‘bubblegummy’ notes work exceptionally with the Neroli and lime in the coke, and it brings a different dimension to back-bar cocktails such as the El Presidente. Obviously, we’re not working with 15 or 20-year-old liquid, so if there was one limitation to the brand this is probably where it lies. I might be tempted to go for something with a lot more cask influence when mixing pure back-bar cocktails especially if I was using premium vermouth, but for a rum which performs well above and beyond its price-point. I’m extremely pleased with what we’ve created here.

Plus the label has a skull on it and the word’s broken up into constituent syllables and it’s got foil on it and sans-serif font and that’s automatically cool. Fin.

A bottle of Dunderhead Rum

Sip it, mix it, you can’t really go wrong here

*We had a lot of traffic to the site around that time. Almost as if people suddenly had lots of time for online shopping. 

**In hindsight it’s reasonably obvious where these rumours came from even hundreds of years ago, brand ambassadors for rival distilleries have been around longer than perhaps we all appreciate…

***’Flavoursome’ is apt here, in many recipes/mashbills the muck is referred to as ‘flavour’ 

****I know what you’re thinking, but no. Get fucked. They’re god’s own drink.