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Whisky Myths Debunked #1 – The Purity of Single Malt — Dramming
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Whisky Myths Debunked #1 – The Purity of Single Malt

by Oliver Klimek on June 16, 2010

I would like to start a loose series of articles on common misconceptions about whisky that are often found among whisky lovers. They may not be sensational revelations for experienced maltheads, but might contain facts that are new to at least some of you.

Single malt Scotch whisky is regarded by many as being superior to blended whisky. This is largely due to two notions:

  1. Blended whisky contains cheap grain whisky which at a young age is usually not at an improvement of taste. This wears off with increasing age, but that’s another story I may tackle in a later post.
  2. Blends are a potpourri of whiskies from usually dozens of distilleries. Single malts allow you to enjoy the product of a single distillery with all of its specific characteristics.

And it’s that second point I want to address here.

Is There Pure Scotch Whisky in the Casks?

As is well known, Scotch whisky is matured in used casks to almost 100%. There is no legal requirement to do so, but in the past centuries, this way of doing it has proven very successful. Mostly used bourbon or sherry casks are used for maturation, and it is no secret that in any “new” empty cask there are up to a few litres of the previous contents hidden in the pores of the wood staves. During maturation, this liquid will slowly diffuse into the whisky, effecticly creating a mix of perhaps 99.5% whisky and 0.5% sherry, bourbon or whatever.

Of course this is not quite the same as pouring a few bottles of other booze into a freshly filled cask because of the complicated phisicyal and chemical interaction between spirit and wood. But everyone should be well aware that any single malt from a first fill cask (or a finishing cask for that matter) contains a notable amount of “foreign” liquids.

Not very exciting so far, I admit. But let’s move on.

And What About Refill Casks?

The Scottish are said to be very tight with their money, that’s basically why they invented this whole used cask buisness in the first place. And they took it even a step further by re-using their old casks after bottling (up to five times for some whisky that goes into blends).

Distilleries can obviously refill their own casks again. So every new malt from distillery X will contain a small amount of older malt from distillery X along with a small amount of bourbon etc. Still not very exciting, I know.

But – and here it starts to get interesting – some distilleries also use casks from other distilleries for refills. Distilleries like Bowmore of Laphroaig are proud of using only first fill casks to get that full injection of foreign booze into their spirits, and they will happily tell you that they are selling their used casks to other distilleries.

Now what does this mean for our single malts? In this case, every refill cask of distillery X will also contain a small but not neglectable amount of malt from distillery Y.

A strinking example is the Glenfiddch Caoran Reserve that was finished in an Islay cask. My bet goes for Laphroaig by the way because they have lots of casks availabe and it is the malt with that kind of peat punch you would like for a finish. They surely wouldn’t have chosen a Bunnahabhain.

Single Malts Can Be Blended Malts

Now technically, we have a vatting of malt whiskies from two different distilleries. This should be properly called Blended Malt according to the current legal definition. But it’s called Single Malt nevertheless. Don’t tell the SWA, or they’ll be going to sue all of those distilleries for breaking their rules…Nah, just kidding.

Am I just nitpicking here? I don’t think so.

Cross Distillery Refills are Worse Than Teaspooning

Some of you might not know the term teaspooning. This is what some distilleries do to prevent the casks they sell to blenders from being bottled as single malts by an independent. For example Glenmorangie is said to have trifled a little of Glen Moray into every cask not going to their botling plant.

Casks “tainted” this way immediately lose their right to be called single malt and have to be sold as vattedblended malts or even blends (when grain whisky is added), even if the actual amount of added whisky is extremely small.

But refill casks from different distilleries contain much more tainting whisky than teaspooned ones, as should have become clear by now. And it is perfectly legal to call them Single Malt Scotch Whisky.

Does anyone in the whisky industry care? I would be very surprised.

Know what you drink!

{ 13 comments… read them below or add one }

gal g June 16, 2010 at 8:06 pm

Great article Oliver.
some very thought provoking points u have there…
waiting for the next posts….



Steffen Bräuner June 16, 2010 at 8:22 pm

Great article

A very peaty Springbank recently made me wonder if they used a cask that previously held Longrow!

Is a mix of Longrow and Springbank single malt ?



gal June 16, 2010 at 8:23 pm


i do think it qualifies as a single malt since it’s a vatting of the same distillery.

was it good? ‘;)


Oliver Klimek June 16, 2010 at 8:29 pm

Steffen, that’s a very interesting question. Legally it will be a single malt without a doubt. But technically it’s a blended malt because of the different distillation methods. Now here we can have a “Single Blended Malt”. If they had separate stills on the same grounds, now that would be a tough case for the SWA lawyers… Is “Distillery” a set of stills or the whole production site?


Thomas June 16, 2010 at 8:54 pm

By law: http://www.opsi.gov.uk/si/si2009/uksi_20092890_en_1#l1g3-l1p1-l2p1-l3p1

Scoth whisky (pure or single malt) must be matured in oak barrel for at least three years.

This statement is incorrect:
“As is well known, Scotch whisky is matured in used casks to almost 100%. There is no legal requirement to do so, but in the past centuries, this way of doing it has proven very successful.”


Oliver Klimek June 16, 2010 at 8:59 pm

Thomas, I beg to differ. My point about the legal requirement is about the word “used”. The casks have to be made from oak, but they do not have to be used. Bunnahbhain Darach Úr is one of the rare examples that are aged in fresh new casks.


Thomas June 16, 2010 at 9:04 pm

That’s correct. It doesn’t have to be “used” cask. Emphasis on the word “used”. : )


Dan March 23, 2011 at 8:05 pm

I’m a little late to the game here but…
Under “Single Malts Can Be Blended Malts” you say that some whiskies that are blends of whiskies from two different distilleries are called Single Malts but should be called Blended Malts. I agree with the “should” part, according to the law. But can you give an example of a whisky that is called a Single Malt and is a blend of whiskies from two different distilleries?



Oliver Klimek March 23, 2011 at 8:16 pm

I am referring to the special case that a distillery re-uses an old cask from another distillery. There is always some whisky from the old distillery left in the cask which mixes with the new whisky during maturation. The whisky regulations don’t care about that, so this procedure does not have to be mentioned and it can still be a single malt. But in reality it is a 98:2 or so mix of whisky from two distilleries.

As an example I mentioned the Glenfiddich Caoran Reserve which ia a mix of Glenfiddich and an undisclosed Islay malt because it was “finished” in an old cask from an Islay distillery.


Dan March 24, 2011 at 9:49 pm

Thanks, Oliver.


Josh Feldman August 16, 2012 at 3:22 pm

When bourbon casks from the US are shipped to Scotland they are not shipped whole. They are unhooped, the staves commoned together, and packed flat. I would wager refill casks from other distilleries get the same treatment – and maybe sherry, port, and wine casks too. Many distilleries keep a coopering staff to reassemble casks – making them whatever size they desire in the process.

My question is this: surely a freshly emptied cask contains up to a few liters of liquid in the wood. But how long do separated staves go before the spirit evaporates nearly entirely? I would wager that few refill casks shipped disassembled have even a single dram of liquid spirit after evaporation.


Oliver Klimek August 16, 2012 at 3:37 pm

For transport, the cask staves are packed tightly onto a pallet which then is shrink-wrapped. So I reckon evaporation during transport to be not much of an issue. And then, evaporation from a porous media is a rather slow process. Fresh wood has to be dried for months until it can be used for barrels. Even though aclohol evaporates faster than water, it would take quite a while until a soaked cask staff is completely dry.


Josh Feldman August 16, 2012 at 9:08 pm

Those are good points, Oliver. The whisky that is soaked deeply in the wood isn’t going to just dry out in a matter of days. However, it’s not going to blend right in to the next batch of whisky either. We’re talking about a subtle diffusion here – not glugs of actual liquid. Clearly the embedded influence of the previous spirit has an impact – and impact that you can taste first fill and for a number of refills afterwards. But that influence is diffusing from traces embedded in the wood – not a normal liquid in the usual sense. Or is it? Jim Beam’s “Devil’s Cut” (which I know you own, have reviewed, and enjoy on the deck with your smoker) is sucked from emptied casks with an industrial vacuum. That’s liquid. I wonder if they sell those vacuumed casks cheaper than they sell the usual ones?


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