It was not until the late
1820s that a new form of still was invented by Robert Stien, which
produced spirit in a continuous stream as long as wine, beer or some such
mildly alcoholic wash was fed into it. First going into commercial
production in Cameronbridge distillery in Fife, Scotland. A Dublin Excise
officer, Aeneas Coffey, attended a demonstration of the new still, took
the idea and developed it further, and it was Coffey's version of the
continuous still that eventually caught on worldwide.
This new still was called
the 'Continuous Still' (also 'Column', or 'Patent',
or 'Coffey Still'). In simple terms, consists of two
columns, one of which has steam rising and wash descending through
successive storeys inside (referred to as the 'Rectifier').
The steam stripped out the alcohol from the wash and carried over to the
second column (referred to as the 'Analyzer') where it
circulates until it can condense at the required strength.
The benefits of the
continuous still is a cheaper and purer spirit.
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Has
two main parts, a 'Rectifier' and an 'Analyzer',
which both resemble tall, wide tubes.
-
They
are both filled with steam.
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The
liquid being distilled enters a pipe travelling down the rectifier,
and is heated almost to boiling point
-
The
alcohol from the primary liquid vaporizes and is channelled along with
the steam back to the base of the Rectifier.
-
Here
it mixes with more steam around the pipes, bring with it more liquid
to be distilled, hence a 'Continuous Still'.
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Roughly
two-thirds up the Analyser, the vapour hits a cold plate condensing it
into a liquid. This is channelled out as a distilled product.
Today,
alternatives open to distillers are to use the labour intensive pot still
which carries the fragrances and flavours of the raw material, or the
faster, cheaper continuous still with its potential for high strength,
pure but tasteless spirit.
How does
it work:
Steam is fed into
the base of the analyser and hot wash into the top. As the two meet on the
surface of the perforated plates, the wash boils and a mixture of
alcohol vapours and uncondensed steam rises to the top of the column. The
spent wash runs down and is led off from the base.
The hot vapours
enter the rectifier at the base and as they rise through the chambers they
partially condense on the sections of a long coil through which wash is
flowing. The spirit vapour condenses at the top of the rectifier and is run
off through a water-cooled condenser to the spirit safe and on to the spirit
receiver. Once the spirit begins to be collected it runs continuously until
the end of distillation.
Because of the rectifying element present in this
process, the distillate is generally lighter in aroma than most Malt
Whiskies. It consequently has a milder character and requires less time to
mature.
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