Pique the Geek 20121118: Scotch Whisky

Scotch whisky is quite different than most other distilled grain spirits.  First of all, it has its own spelling.  Except for Scotch, the spelling is “whiskey”.  In the case of Scotch, it is “whisky”.  I do not know if that is a Gaelic thing, but it is true.  Likewise, the plural of “whisky” is “whiskies”, whilst the plural of “whiskey” is “whiskeys”.  Actually, these distinctions are at best approximate, as some American brands of things that are not Scotch call themselves “whisky”.  But Scotch is almost always spelt “whisky”.

Actually, I am not sure if “Scotch” should even be the name for it.  Some of them call themselves “Scots’ Whisky”.  That might be a better way of saying it.

Now for the Geeky stuff.  Follow with me for several hundreds of years?

First the word.  Regardless of the spelling, it is sort of kind of derived from the Gaelic usige beatha, or water of life.  That sort of rolls in with the more Latin aqua vitae, still used in some of the low countries for their own distilled drinks.

But this is about Scotch.  It is a unique spirit, and is wonderful.  I say “it”, and that is in error.  There are scores of variations.  Let us look at whisky (and I use the Scottish spelling) first in general.

Whisky is defined as a distilled product derived from grain, but that is not a sufficient definition.  Gin and vodka can also be made from grain, but have very different characters than whisky.  The difference is that whisky undergoes an aging process, usually in oak, whereas the “white” spirits are bottled straightaway after distillation in most cases.  Brandy is produced from grapes (although other fruits can be used, with the qualifier of the name of the kind of fruit used).

Just about anything that can produce sugar can be made into spirits.  Potatoes are sometimes used for vodka, and people have always been quite creative in producing distilled beverages.

Scotch whisky is, like other whiskies, produced from grain.  There are two basic types of Scotch whisky:  malt whisky and grain whisky.  By regulation, malt whisky can be made from only malted barley, water, yeast, and caramel (burnt sugar) color.  Malted barley, or just malt, is barleycorns that have been steeped in water and allowed to sprout.  It is then kilned to arrest the growth of the seedling and to dry it to prevent spoilage.  Malting is quite an elaborate process and most distilleries purchase their malt from vendors who specialize in it, although a few distilleries produce some of their own malt.

Grain whisky is made from grains other than barley, but most of them do contain some malt for reasons to be discussed later.  Sometimes these other grains are sprouted, sometimes not.  Usually around 15% or so of malt is used, and it is actually critical.

The malting process causes enzymes to be developed that convert the insoluble (and unfermentable) starch in the grain to sugar, in this case the sugar maltose.  The enzymes are collectively known as diastase, and barley develops the highest diastatic activity of any other grain.  This is why barley is so essential for whisky (and beer) making.  Barley has such a high activity that only a small amount (the 15% previously mentioned) is required to convert the starch from other grains to maltose.  Yeasts can ferment maltose to alcohol and carbon dioxide, and the initial steps for making whisky are quite similar to making beer, but less elaborate since in the case of whisky the fermented solution is to be distilled whislt for beer is is drunk as is, after some aging.

Here is where Scotch is different from all other whiskies:  the malt is kilned in many cases by exposure to smoke from a fire using peat as the fuel, giving it a unique nose not seen in any other spirit.  Not all malt is peat kilned, but much of it is.  Now comes some further distinction in the various kinds of Scotch.  Peat is simple partially decomposed vegetation, particularly that of Sphagnum mosses.  Peat is common in Scotland, and the water itself in many regions has a peaty flavor as well, so without peat there would be no Scotch as we know it.

Until late in the 1700s most Scotch was malt whisky, but malt is expensive.  This is why other grains were explored.  However, the flavor is quite different and not at all like what we think of as Scotch.  Early in the 1800s a new technological innovation was introduced that make it possible to produce almost pure alcohol (it is not possible to prepare 100% alcohol by distillation for reasons to be explored in a minute), devoid of flavoring materials and other impurities.  The continuous still made it possible to use any source of starch (or sugar) to produce alcohol devoid of any character.  Ordinary vodka is such an example, and it is simply diluted grain neutral spirits.

It turns out that the continuous still was a boon for Scotch production.  Since the more expensive malt could be only a small fraction of the grain making up the product, it became less expensive to produce.  This became important in the mid 1800s because of the essentially complete destruction of European vineyards by the insect phylloxera.  All of a sudden wine became rare and expensive, and brandy and Cognac did so as well.  Blended Scotch became extremely popular during this time, and is still savored by many.

A continuous still is operated under strictly controlled conditions and is designed such that 95% alcohol (by volume) can be tapped at a particular place in the condenser.  Components with lower boiling points are separated by temperature, as are components with higher boiling points.  The reason that it is not possible to produce 100% alcohol by distillation is that a mixture of 95% alcohol and 5% water has a lower boiling point than pure alcohol.  Such mixtures are actually very common in distillation, and they are called azeotropic mixtures.  It IS possible to produce 100% alcohol by distillation, but it involves adding a third component, like benzene or toluene to form a ternary azeotrope with yet an even lower boiling point.  This is distilled until all of the water is removed, then the other component is separated.  Most 100% alcohol these days is produced by physical drying agents, such as molecular sieves, that physically trap the water in pores within ceramics.  The larger alcohol molecules are too big to fit into the pores, and the water is strongly bound by hydrogen bonding within the pores.

While grain neutral spirits have no character of their own, they are great for blending with other, more highly flavored whiskies.  Originally, all Scotch was single malt whisky, distilled in pot stills.  A pot still is what you see on TeeVee on those horrible TLC moonshining shows.  In a pot still, conditions are not nearly as controlled as in a continuous still and the distillate changes with time (as alcohol is distilled out, the temperature rises).  Instead of 95% alcohol, the distillate from a pot still can vary widely, from 95% at first (rarely attained) down to zero.  Since the materials that give flavor have boiling points different from alcohol, pot still distillates carry with them lots of these components.

Now, some of these components are toxic (like methanol) or irritating (like acetaldehyde).  These particular two are lower boiling than alcohol and come out of the still first.  These high shots are generally discarded, but can be reprocessed to recover some of the alcohol that does distill out with them.  After the high shots comes the “goodie”, mostly alcohol and water with some flavoring components.  As more and more of the alcohol is depleted from the pot, the temperature rises as the water content in the distillate increases.  At some point collection of the “goodie” is halted, and the feingts, containing just a little alcohol, are collected for redistillation to recover as much of it as possible.  In practice, the high shots and feingts are often reprocessed in continuous stills because of the much greater efficiency of them.

Let us get Geeky for a minute.  The efficiency of a distillation process is described by a term called a theoretical plate.  The most efficient pot stills have maybe three or four theoretical plates, whilst well designed continuous stills can have hundreds.  This all has to do with vapor/liquid phase equlibria, and operating conditions strongly affect the number of theoretical plates.  Taken to the extreme, a modern capillary gas chromatographic column can have scores of thousands of theoretical plates, but their capacity is tiny.  Think of Abby Schuito on NCIS and Major Mass Spec.

To make up for fewer plates, multiple distillations are often done to increase efficiency.  In other words, distilling the distillate in a pot still with, say, three theoretical plates is roughly equivalent to distilling it once in a six plate still.  Pot distilled Scotch is often distilled twice, the final average alcohol content being around 60% to 70% alcohol by volume.  More distillations can be done, and very high alcohol contents can be had, but as this is done the character of the whisky begins to approach that of grain neutral spirits.  The level chosen produces a whisky with character, especially when peaty water and peat kilned malt is used.

For single malt Scotch, this distillate is diluted with (often peaty) water to 63.5% alcohol by volume and put in oak.  By regulation, Scotch has to be aged in oak for three years and a day, but many are aged for longer, sometimes much longer.  As a general rule a thumb, the older the whisky the more expensive it is.  There are two reasons:  first, oak is porous and evaporation occurs.  Since alcohol is more volatile than water, the alcohol content of the contents of the barrel decreases.  The second reason is that it takes space and barrels to age the whisky, and this ties up material and capital.  Thus, older liquor is costlier to produce.

After aging, the whisky is removed from the oak (oddly, the majority of Scotch whiskies are aged in bourbon barrels from the US, since by law bourbon must be aged in NEW, charred oak and Scotch can be aged in used barrels) and for single malts is blended with other, aged whiskies produced at the same distillery.  These are the premium Scotches like The Glenlivet.  The age marked on the bottle is by regulation the age of the youngest whisky in the blend.  The actual amount of single malt Scotch is very small.  Most Scotch is what is called blended Scotch, probably over 80% of Scotch on the market being blended.

For blended Scotch, a relatively small amount of malt whisky is blended with larger amounts of continuous still product.  Now, the continuous still material has little character of its own, but it does pick up flavor and color during the aging process from the oak.  Depending on the distillery or blender, more or less of the expensive, highly flavored material is mixed with the spirit of less character.  Actually, most people prefer blended Scotch because it has a milder flavor and nose than single malt has.  If it were not for blended Scotch, it would be so expensive that only the wealthy could afford it.  Each producer of blended Scotch has its own recipe, and usually several varieties are blended to produce a consistent product.

Traditionally, Scotch has been considered to be one of the following types.  Lowlands, often triple distilled in pot stills with a medium flavor, Highlands, peat kilned and double distilled, with a full flavor, Isleys, with an extremely smoky flavor, and the Campbeltowns with the most pronounced smoky flavor.  Various combinations and amounts of these four flavor stocks are blended with the continuous still product per the specifications of the blender.  I like the blend in Old Smuggler Scotch, a quite a good Scotch for a reasonable price.

Whether or not single malt or blended, Scotch (like all whisky) does not undergo any further improvement once in the bottle.  With no organics and salts to extract from the wood and no evaporation, no change is possible.  The alcohol content is so high (typically 40% to 45%, with some exceptions, alcohol by volume), no microbes can survive as is the case with wine, which continues to change in the bottle.  Thus, if Grandpa gave you a bottle of eight year old Scotch 50 years ago (and you still have it), it is still just eight year old Scotch.

There are a couple of other legal distinctions about Scotch whisky.  First of all, it has to be distilled, aged, and bottled in Scotland.  We already talked about single malts whisky, defined as whisky produced at a given distillery.  Sometimes it is from a single barrel and sometimes it is a blend from many barrels, but always from a single distillery.  Blended Scotch is as just described above, a blend of several flavor stocks and the more neutral continuous still product.  Now it gets a little trickier.

Single grain Scotch does not mean that it made from a single kind of grain.  All grain Scotch is made from two or more cereals and is usually distilled in continuous stills.  Single grain Scotch means a blend of grain Scotches produced a a given distillery, although there is no rule against bottling whisky from a single barrel.  It just means that if it is a blend, all of the whiskies have to be from the same distillery.

Now there is blended grain Scotch, which is a blend of grain Scotches from two or more distilleries.  Finally, there is blended malt Scotch.  It is like single malt Scotch except that the malt whisky comes from two or more distilleries.

In all cases, distillers and blenders strive to provide a consistent product to fulfill consumer expectations. Actually, there is an exception.  Some single malt Scotch is, as I said earlier, taken from a single barrel.  Since each barrel is unique, there will be by necessity some variation.  Other than this, though, consistent products are sought.  This is the most difficult for single malt Scotches because only a single kind of whisky from a single distillery can be used.  This becomes increasingly more difficult as the age of the whiskies gets older than, say, eight years since there is less stock available for the economic reasons mentioned earlier.

At the other end of the spectrum, blended Scotch is much easier to keep consistent because there is no restriction as to what blending stocks can be used, as long as all of them were produced in Scotland.  Lots of blended Scotch is only three years old, but that applies mostly to the grain Scotches that have little distinction.  Often older single malts with more character are used, but remember, by regulation the age of the youngest whisky in the bottle goes on the label.

Now that we know a little about how Scotch is made, how do we drink it?  Traditionalists insist on taking it at room temperature, undiluted, with perhaps water on the side.  I prefer that method for something like a fine single malt (I am partial to The Glenlivet, but it is EXPENSIVE).  Such whiskies are in the same class as fine Cognacs, meant to be sipped slowly and the nose of it savored.  For lesser Scotches, like typical blended whiskies, I generally like a little ice and seltzer, sometimes with a lemon or lime wedge.

Because of its unique nose, Scotch has less utility as a mixing liquor than the white liquors or even bourbon whiskey.  Scotch does not play well with sweet, but bourbon does because of its high vanilla notes (from the oak, and most of the vanilla fragrance is leached out by the bourbon, so the used barrels in which Scotch is aged do not have much).  That is not to say that there are no sweet Scotch cocktails, just not as many as with the white spirits and bourbon.  It is sort of wrong, at least to me, to take such a unique sensory material and mask it with other, powerful flavors and scents.

I guess I am like the Scot in this apocryphal (probably) story about how he did not understand American drinking habits.

They put whisky in it tae make it strong,

then they put water in it tae make it weak.

They put spice in it tae make it hot,

and ice in it tae make it cold.

Then they lift the glass, say, “Here’s tae ye”,

and drink it themselves!

Finally, it is not really known when Scotch whisky as we know it was developed.  The first document that specifically refers to it is the tax book from 1494, and a large quantity of whisky was mentioned.  It is probable that its history goes back considerably longer, both as a kitchen product and a commercially produced one.

I hope that you have enjoyed this brief survey of Scotch.  If you are a Scotch drinker, I am sure that you have your favorite brand.  Right now I have a bottle of House of Stuart, a mediocre blend given to me by a neighbor after I did a favor for him.  Old Smuggler was hard to find here until recently, when I spotted some at the store.  I have not gotten any yet as I do not drink much Scotch any more.  I did have a couple of sips last night as I was preparing to write this piece, as inspiration for the author.

That about does it for tonight.  I shall be available for comments tonight, unless I am not.  If that be the case I shall join later.  I shall also return sometime tomorrow night for Review Time.

Warmest regards,

Doc, aka Dr. David W. Smith

Crossposted at

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  1. a drink with a long history?

    Warmest regards,


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