Eh? Say what? Yeah, flocculation, or as us laymen know it as: “stuff” in your rum. I’m not talking about sediment, that’s bits of cask, char and other little particles that are not taken out through filtering and enter the rum after it has been casked. No, no, this is all together other “stuff”. It can take various forms from floating or sinking small white lumps to suspended cloud like substances.

So I’ll start from the beginning. This post was inspired by a bottle of rum I have that is giving me comedy moments; a bottle of a single cask Caroni (16 year old, bottled by Gleann Mor), basically it’s flocking like no one’s business – more so than any spirit I’ve ever had a bottle of and to the unaware person this is something that looks really, really weird. This is the bottle and this is what it can look like (it’s a crap picture I know):




So what am I going on about?

Firstly 95% of rum drinkers won’t ever see this, or if they do then it’s likely to be so mild that it’ll be shrugged off, however 5% of us (those who often buy bottles of single casks or unfiltered heavy rums) will see this at some point.

Making a distilled spirit isn’t quite as straight forward as making your mash, producing wort, fermenting it with yeast, distilling the wash and collecting what is produced. It’s really, really, complex and frankly I don’t understand the fine points at all! As part of what happens during fermentation fusel alcohols are produced (not desirable) and these combined with organic acids to produce esters. Esters are what makes a spirit smell and taste of what it smells and tastes of (your cinnamon, banana and pineapple notes are esters).

There are 2 types of ester; acetate esters (acetate+alcohol) and ethyl esters (ethanol+fatty acid). Medium-long chain ethyl esters will give an oily and waxy texture. After distillation there are fatty acids left in the new make/spirit, these are specifically what causes a spirit to turn cloudy when the spirit is diluted and/or it’s temperature drops. People don’t like cloudy rum or whisky, they want a clear and crisp clean bottle of booze so the distilleries (more often than not) chill-filter the pop before they bottle it. This removes a lot of the fatty acids that cause the problem, but as these also contribute to the texture of the spirit and help to carry flavour, chill-filtering can be detrimental to the resulting taste profile (ie it’s not as ‘good’).

I really don’t like chill-filtration. These compounds that are being taken out are the good stuff! It’s like your organic knobbly dirty carrot, people won’t buy it at the supermarket because it doesn’t look as nice as the clean, straight and uniform ones, but I tell you which one will taste better! I don’t buy rum to look at it, I buy it to drink and enjoy so I want it to taste as natural and as full of flavour as it can.

So what is flocculation and what can you do about it?

It’s the process in which colloids (let’s call “stuff” for the purpose of this) come out of suspension to form flocks. It can be due to adding a clarifying agent, like in water treatment, or it can happen spontaneously. We’re talking about spontaneous flocculation here.

As a spirit is diluted down it’s able to hold less “stuff” in suspension. Water isn’t as good at this as ethanol is and dilution is increasing the water in the water:ethanol ratio. Also, as temperature falls the “stuff” moves around less and can start to clump together. The more flocks there are then the more those flocks pick up other flocks and the bigger they get, so they pick up and join more flocks. The more “stuff” you have in a spirit then the more flocking can occur, which tells me one thing about my muse here; this Caroni has A LOT of “stuff”. It’s not even diluted, it’s full cask proof at 50.2% abv, and if it’s flocking this much then that can only mean one thing; BIG flavour and texture. This is going to be a very heavy rum.

Ok, I must admit it doesn’t look very nice but it’s perfectly fine and safe to drink. So what can you do about it? Well you need to understand the cause. If it’s happened in a glass because you have added too much water then there’s not much you can do apart from adding less water. It’s unlikely to happen however as it needs time and your glass isn’t going to be sitting around for long enough! If it’s because your bottle is cold, as was the case with mine, then warm it up. Move it somewhere that is just below room temperature so it doesn’t get as cold and once it’s warmed up a bit give the bottle a gentle shake – the “stuff” will go back into suspension and the flocks will disappear.

So there you go. If you get candy floss floating about in your single cask, or lumps of small white bits, you now know what it’s likely to be and how to sort it out………..you also know you’re going to have a full flavoured rum!

It’s worth pointing out at this point that this all applies when you are happy with the provenance of your bottle, ie it’s come from a reputable place (decent shop, trusted online retailer, supermarket etc). If you got it on the quiet from your mate Dave, then it may be bad booze 😉

3 responses to “Flocculation

  1. Same for my bottle….

    But one question, I’ve bought a sampler of this caroni too and I taste it yesterday… Waw, really the same in noose and taste than the velier 12 years.

    So two questions:) My noose is really really bad or they ‘ve made mistake during the sampling process ? What do you think of the bottle ?

    best regards,



    • I doubt there is a mistake during sampling, I also doubt there is a problem with your nose 🙂 The problem is that both are quite intense and powerful. The single cask is an example of one of the many casks that make up the Velier bottling as they are a blend of quite a few barrels, Velier being tropically aged of course. So it’s natural that one would remind you of the other.


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