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 😉


I’m not really into drinking grog out of the bottle, which means I need to find something to put the stuff in before it can be guzzled down. Rum, being a liquid, can be drunk out of any watertight container but does it really make a difference what that container is? Well, yeah. I mean, by all means drink rum out of a coffee mug if you want to (it’s your rum) but I’d suggest that you won’t gain much from the experience other than a slight light-headedness (or raging hangover)……depending on how responsible you are. If you’re drinking a “sipping” rum then you’ll ideally be wanting a glass.

Here are some glasses:


All different shapes right, so which one should you use and why does it matter? The answer all depends on how you are drinking your rum and what you want to get out of the experience.

The general rule of thumb is; if you want to get the most out of the aroma (nose) and taste (palate) then you need a glass with a rim that tapers inwards, and ideally a bowl type shape at the bottom – a tulip glass. If you want to mix your rum with anything other than water (ice or a mixer) then you need a glass that is wide enough to accommodate the volume. As the mixer and/or ice will hide the finer aromas you don’t need to be too concerned about an inward taper on the rim.

Tulip glasses:

These have a bowl at the bottom and taper in at the rim. This lets you swirl the rum without it spilling, which agitates the liquid and releases aroma compounds, and it also forces the aromas together at a point just above the middle of the rim so as to concentrate them. It also stops any of the aromas whizzing off anywhere unwanted – if they want to get out of the glass then they are going to have to get past you nose.





The Glencarin. My personal favourite. Small bowl and nice taper to the rim. Focal point is just outside the top of the glass in the middle of the opening, I find this offers the best of the nose:








The Copita style glass. Similar to the Glencairn but with a stem to hold. Some have a flare at the rim, others taper in more at the rim and less of a bowl, but they are essentially the same. Often a better nose with a narrower rim but you loose some of the palate with this. Taste is a mixture of smell and taste you if the rim is too narrow then you can’t smell when you sip, so you sacrifice palate:









The Brandy snifter. Er….a brandy glass. Wider bowl and not as narrow at the rim, gives a nice swirl but doesn’t concentrate the nose as well:






These are short, wide and sturdy glasses. Some taper a bit, some flare a bit, but generally they are as wide at the top as they are at the base and allow enough room for ice to be added or to hold the extra volume when a mixer is added.


Miscellaneous glasses:

There are many other random shaped glasses out there, most of which are a combination of the other glass types. Here is a glass I have that is an example of a crossover between a tumbler and a copita style glass. It’s as wide as a tumbler but has a thick stem and slight taper with a flare to provide a basic swilling bowl:


My choice:

Personal preference and all that. I always use a Glencairn when reviewing. This is because  I came from whisky and it’s a pretty standard whisky glass, but also because I know it well. I know how to get the nose and palate right and consistent in it and how to use it to change what I experience. When drinking and not reviewing I usually alternate between the Glencairn or a Copita depending on mood. There are times though that I will sit with my hybrid glass (above), full of ice and a sweeter no-brainer rum, in the sun and just chill.

……oh, all my glasses are crystal by the way. I find this is just a nicer glass to hold due to weight.

46% is the magic number

….but some spirits are bottled at 46% abv!!!

A lot of people harp on about chill filtration in spirits, personally I’d rather my spirit to be not to be chill-filtered, but almost everyone glosses over the 46% abv fact that usually comes with it. They just accept it’s part of the package but don’t know why. It’s likely it is because spirits can go cloudy under 46% abv when temperature drops, unless they are chill filtered, so once you’re over 46% you don’t need to do it. Any other reasons for 46% though? You bet:

[Entering geek mode] Some time back I was looking into interesting factoids around aged spirits, as one does when one is an enthusiast and has a bit of spare time. One of the most interesting pieces of information I found came from a study in thermodynamics (“Rheological study and thermodynamic analysis of the binary system: Influence of concentration” by R. Belda et al).

Basically (very basically!) ethanol is thin – that’s what comes out of the still. Water is thin – that’s what they mix with the distillate to get the spirit to bottling strength. The more ethanol there is in a water/ethanol mixture then the thinner the mixture, likewise the more water there is in the same mixture then thinner the mixture. You would think that if the mixture was 50/50 then that’d be all good, right? Wrong.

Most spirits (in the UK anyway) are bottled at 40% abv, this is a nice figure, the mixture isn’t thin – if you swirl your glass you’ll get some beading – but when you start to increase the level of alcohol away from 40% something magic happens.

If you mix water and ethanol together the point at which the viscosity of the resulting mixture reaches its maximum is at 46% abv. 46%. And this holds true when tested at a large range of temperatures too. This is known as maximum viscous synergy. Any more than 46% and you start to get a thinning of the mixture again.

So, is this why you get “naturally” presented, or “craft” bottlings at 46% abv? In my view, yes – and most likely this added bonus of viscosity is just a pure accidental by-product of the fact that putting things to 46% abv means you don’t have to chill filter. Humans like texture, it makes a big difference to the way we experience taste. So there you go, a bit more of the science behind that particularly odd bottling strength of 46% abv. It truly is a magic number.

…………I might add that this all goes to pot when you start adding other stuff into your spirit, such as sugar. You can get a nice viscous mouth-feel by loading your spirit with sugar, but that’s going to impact the flavour delivery and it’s frankly cheating 🙂