So, WOOD plays a crucial role in the development of a 'modern' single malt.
First of all there's the kind of OAK used by the COOPER to make the casks.
Only oak casks are used. Not only because it's a legal requirement; oak is
flexible and solid at the same time while it adds very distinct elements to
the spirit inside as well. Just do a search for 'oak wood' on the main page.

But unlike a fine wine, a malt whisky hardly ages or changes
once in the bottle. Interestingly enough, the fact that it does
mature in oak casks was discovered only by accident. In the
old days wooden casks were used merely as vessels for the
freshly distilled spirit. A lot of the spirit was consumed before
it ever got the chance to evolve into anything that smelled or
tasted like the whisky we drink today. Nevertheless, here and
there some casks were left alone long enough to age in peace.
Nowadays they let the wood work its magic for at least 3 years.

Just like a fine wine, a malt whisky is shaped by many different
influences; the type of water at the distillery, the shape and
size of the pot stills, the climate within the warehouse, etc.

TIMING is probably the most important element in the single malt equasion.
Deciding when the whisky in the cask is ready to be bottled is no easy task.
Whisky has to be stored in oak casks for a minimum of three years. This is
a minimum set by law, but usually the malt gets a chance to develop much
longer. Casks that are reserved for blends are usually matured for anything
between three and ten years, but the casks that will be bottled as single
malt can stay in the warehouse for much longer. Different malt whiskies
reach their peak at different ages. Many malts leave their wooden wombs
at the age of 10 or 12 years, but some are stored for 25 years or more.
Some warehouses even contain casks of malt whisky that was distilled
even before WWII. Needless to say that given the shortage of whisky
during the war and the thirst of the Scots, not many casks survived...

Some people argue that STORAGE is a important factor in the life
of a cask of whisky as well. Things like the type of warehouse, the
location of the warehouse and even the location of the cask within
the warehouse. Not everybody is convinced of the relevance of the
storage conditions, though. It's hard to distinguish fact from fiction
and observation from imagination when it comes to malt whiskies.
When you know a distillery is located on the shore it's easy to find
coastal elements like salt and fish in the whisky they produce.

Almost every cask that's used for the maturation of whisky has been used
before in the production of BOURBON or SHERRY. About 90% of all the malt
whisky that is distilled in Scotland ends up in casks that contained bourbon
before they were shipped from the USA. That makes a lot of sense, because
American law dictates that a bourbon cask can be used only once for the
production of bourbon. After that, the cask becomes useless to the bourbon
distillers and the Scots can pick it up for a friendly price. Most other single
malts have been aged in (more expensive) sherry casks, mostly from France
and Spain. After the finishing fad hit Scotland a few years ago we've also
seen single malts that were 'finished' (or even completely matured) in more
exotic cask that used to hold port, madeira, cognac, Cuban rum and even
various wines like iquem, bordeaux, sauternes, chardonnay and chenin blanc.

Every cask BREATHES while it matures. The wood of the casks
expands during the heat of summer and contracts during the cold
of winter - not unlike the private parts of any kilt wearing Scotsman
who's minding his sheep, I would imagine. As a result of evaporation
the spirit will annually lose up to 2.5% alcohol while it matures.

The standard ex-bourbon cask holds 200 litres of
whisky, is usually called a BARREL and has been
used only once for the maturation of bourbon in
the US before it was taken apart and shipped to
Scotland. There are many different brands (Jack
Daniels, Jim Beam, George Dickel, Maker's Mark,
Four Roses, Old Crow, Cold Turkey, etc.) but all
bourbons are actually produced at just a handful
of distilleries. The exact heritage of the bourbon
casks is considered a topic of minor importance,
which seems rather odd when you look at all the
fuss that is made about to trouble some blenders
go through to secure just the right sherry casks
for their compositions. Bourbon barrels are usually
heavily charred on the inside. Not only does the
carbon from the burnt layer act like a filter that
removes certain nasty elements from the spirit, it
also helps to transfer vanilla and woody notes to
the bourbon. In its 'second life' in Scotland a cask
 keeps influencing the contents, although the
effect diminishes over time. This is especially
true when a cask is used more than once.

When it comes to casks, SIZE matters as well.
In a smaller cask, the surface of the wood interacts with a
relatively small volume of whisky. This results in a relatively
fast maturation compared to larger casks. A 500 litre sherry
butt has to 'convert' much more spirit than a 'small' 200 litre
bourbon barrel, while its surface isn't significantly larger. But
then again the effects of bourbon casks are different from
those of sherry casks. And as we all know it's not just what
you've got, it's how you use it that's most important.

Sherry casks are larger than bourbon barrels and
come in several different sizes. A HOGSHEAD holds
250 litres while a BUTT is twice that size with 500
litres. Distilleries sometimes use other sizes like the
450 litre PUNCHEON as well, but the large majority
of the casks are still barrels, hogsheads and butts.
Just like the discovery of the benefits of maturation
in oak casks the blessings of sherry were uncovered
by accident. Scotland relied on oak from the English
forests for a long time but at some point distilleries
needed to find an alternative source for their casks.
Sherry, a fortified Spanish wine, was very popular
on the British isles at one time. Actually, it still is.
Even today the UK takes care of 29% of the world's
sherry consumption with Holland coming in a close
second with 27%. There are many different 'types'
of sherry which means there are different types of
sherry casks; Fino, Manzanilla, Oloroso, Amontillado,
Pedro Ximénez, etc. Are you dizzy yet? No? Good.
Then you might be interested to learn that Pedro
Ximénez is also the name of one of the two grape
species used for sherry - the other one's Palomino.

Anyway, sherry used to be shipped from Spain to England by
the cask. Alcoholism was running rampant in those days, so
empty, discarded sherry casks were littering the 19th century
English landscape very much like empty beer cans and bottles
are doing today. In one of the world's first recycling initiatives
the Scots started picking up those second hand sherry casks
to use them again for the aging of their whisky. And then use
them again and again. These days, both bourbon and sherry
casks are used more than once. A sherry cask that has seen
four or five fillings is no exception. When a cask has held and
ages whisky for the first time it's called a FIRST-FILL cask,
after the second filling it's a SECOND-FILL cask, etc.

A cask has only so much 'character'.
With each filling less and less of its charcter
is transferred to the whisky. Depending on
the pedigree of the cask it will become 'tired'
and eventually 'exhausted' after a couple of
fillings. These casks are usually referred to
as PLAIN WOOD. But sometimes casks are
'rejuvenated' by charring them again and/or
filling them under high pressure with sherry
or paxerette (boiled, concentrated sherry).
That doesn't sound very traditional, does it?
Well, it's just a tradition that has evolved...

MM Interview with Olivier Humbrecht
MM Interview with John Glaser
E-pistle: Pro's & Con's of Old Age
E-pistle: The Influence of Age
E-pistle: Ages of Macallan

The part of the spirit that vanishes between casking and bottling is called the ANGELS SHARE. But some angels are thirstier
than others, it seems. The Saint Magdalene 1979/1998 in the UDRMRM series still had an alcohol percentage of 63.8% when
they bottled it after 19 years, but other malts are in danger of dropping below the legal minimum of 40% in their mid-20's.

So now you probably think you know what's so great about single malts, eh? You don't know half of it, mate!
Well, actually, you DO know half of it now - you are exactly halfway through this Beginner's Guide.
Click onwards to the next chapter of this guide, dealing with the actual bottling of single malt whisky.

I can only imagine the drunken delight of the lucky Scotsman who discovered the secret of maturation...

Just like all French cognacs have been matured exclusively in Limousin oak casks, only a few
species of oak are used for whisky casks - white American oak and European oak. But not only
the type of wood is important; the cask's HISTORY plays an even bigger part in the process.
'Fresh' oak casks have actually been used in the past, but the current wisdom says that the
woody elements from a virgin cask would overpower the subtleties we appreciate in a whisky.