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 🙂

One response to “46% is the magic number

  1. This is incorrect, because the % alcohol is listed on bottles as alcohol by volume, whereas the paper you cite lists their data as percent alcohol by weight. The formula for converting between ABV and ABW is ABV x density of 100% alcohol in g/cm^3 = ABW x density of the alcohol/water solution in g/cm^3. The density of 100% ethanol at 20C is 0.78934 g/cm^3, and the density of 46% ethanol in water by weight at 20C is 0.92257 g/cm^3, so 0.46 x 0.92257 / 0.78934 = 53.8% ABV. However, maximum viscosity will likely be perceived significantly above this ABV because the spirit is instantly diluted by saliva upon entering the mouth. More likely 46% is common as you said for reasons having to do with avoiding cloudiness.

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