Cask strength whisky - What exactly is cask strength?

[albo]

While reading the internet this lunchtime (on my own time boss if your reading), I happened upon an article which discussed cask strength whisky and what new make spirit was diluted down to before maturation. Apparently this is 63.5% abv as an industry standard, who knew? Not me I know that much.

Upon reading that, I did some more digging and found there seems to be no formal reason for this, the best educated guess I can find is that whisky matures faster at a lower abv, the optimum being 60% but the risk of it loosing too much alcohol during maturation and coming out lower than 40% is too high, so they settled on 63.5%.

This leaves me and others I have spoken to (hello bifter) in a quandary about a few things. Assuming the above is correct (if not then this thread is dead before it even started), then, I come to the conclusion that each barrel must loose alcohol at an undetermined and non constant rate, as if it were a constant all, say 10 year old, cask strength whisky would be the same ABV after 10 years. I'm guessing that climate, differences in wood, where it is stored in the warehouse etc all affect this?

That said, if the comment about 60% running too high a risk of loosing too much alcohol and thus going below the 40% abv mark is true, how is it we see 20+ year old bottles of cask strength whisky up at over 60%abv? You'd have thought that they would have lost more than 3.5% abv over a 20 year period, no?

The only exception from this I can find is Bruichladdich, who by all account fill the barrels at the same level that comes out of the stills, as they 'can't afford to store water'.

So I guess I'm asking if anyone knows anything more about this, there are plenty of you here who are either well connected in the industry of have been about it for longer than I and I was wondering if you could shed any light on this?

Thoughts?

[Alastair]

My understanding is that it is industry standard to fill casks at 63.5%, but I don't think it comes out the still a great deal higher than this, obviously it will vary from one distillery to another but I recall a figure of around 70% or low seventies for double distilled spirit.

The alcohol level is very much dependent on the quality of wood and storage conditions and obviously the time in the cask..

The bottle which amazed me just this past week is the Glenlivet 70 Year Old from G&M, 45.9% abv after 70 years in the cask.

My understanding is that CASK STRENGTH is the strength it comes out the cask but what I have always wondered is do some whisky companies round off the strength of the whisky yet still state it is cask strength. For example the excellent 1st travel retail bottling Old Pulteney WK499 Isabella Fortuna was bottled at a cask strength of 52% abv exactly, now this wasnt a single cask bottling so whats the chance of a number of casks vatted together being exactly 52%. Do they sometimes round off the abv with a drop of water if so then technically it isn't cask strength.

[Alexppp]

[Keith]

[Alastair]

Cheers Keith, that makes sense, i hadnt thought about it like that.

[Genuine Risk]

This is off the top of my head but I think the tolerance for whisky ABV is 1.5%. I.e. What it says on the label could be 1.5% either way.
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Putting the func in dysfunctional.

[Gregor]

[Alexppp]

[Big Mac]

[Genuine Risk]

[Genuine Risk]

And to blow your mind you might not even be getting the full 700ml or 750ml in your bottle, not saying it happens in whisky but a lot of companys use this law on tolerance to make lots of extra cash.
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Putting the func in dysfunctional.

[albo]

What a depressing read that was this morning, I've often seen some bottles who's fill level was slightly different. Now I know why

As for the origional debate, it's been an interested read and I thank everyone for their input.

[Genuine Risk]

[albo]

Thanks very much for that, it's certainly something I didn't know.

It makes me wonder though when it comes to cask strength whisky, why they put the decimal point at all in that case, assuming it's the 1% allowance, then why not round it up / down to make lables easier to print etc? Or is it to give the consumer something that sounds a bit more 'fancy'?

[bifter]

I was surprised to learn how consistently this practice is applied across the industry. There is certainly a great variance in abv among whiskies of the same age following maturation though. The point about Bruichladdich seems to be borne out as many of the recent SMWS Port Charlotte releases were about 65% at 8 or 9 years.

Some other SMWS bottlings are at a strength that belies the years, e.g. I had a Glen Moray 22yo at 61%. Could this (and the 70 year old Glenlivet at 45.9% that was mentioned and many other 40 and 50 year old whiskies) have been specifically casked at high strength in order to mature slowly?
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"Whisky is liquid sunshine."
[George Bernard Shaw]