Continuous, Column, Patent, or Coffey Still are various titles for the same thing: continuous distillation in a column patented by Aeneus Coffey in 1830.
There have been various arrangements and improvements over the intervening 190 years or so, but the principle of efficient, continuous, fractional distillation over a more costly pot still distillation still stands today.
Upon its invention by Robert Stein and improvement by an Irish exciseman, Aeneus Coffey, it has been a contentious invention. Immediately Dublin’s pot still distillers turned their back on the invention fearing, quite rightly, that it produced inferior spirit quality. The Scots, though, adopted it with alacrity.
Even in Scotland it was a divisive issue, one fought in the courts. Many doubted whether this bland, ‘silent’ spirit even merited the title of whisky at all. What it did mean, though, through advances in blending, was that expensive, flavoursome pot still spirit could be ‘stretched’ with cheap and cheerful column still spirit to make a whisky cheap palatable to the masses in both taste and price. The column still was responsible for the enormous success of blended Scotch whisky that took the world by storm in the nineteenth century.
Essentially a column still consists of two parts, sometimes one on top of the other like an Apollo rocket, otherwise separately, side by side: the first has steam rising to extract alcohol from descending wash; the second has this alcoholic-rich vapour rising up it and condensing at varying strengths the higher up the column it reaches.
COLUMN STILL DISTILLATION PROCESS
Distillation starts with pre-heated wash (fermented cane juice in our case) introduced at the top of the wash still, and steam to the bottom: the steam rises, the wash falls. As the two meet on the surface of a series of perforated plates throughout the height of the column, the wash’s alcohol vaporises and together with steam rises to the top of the column. Spent wash, stripped of its alcohol, is drawn off at the base.
WASH COLUMN SIEVE PLATES
All the alcohol vapour – there is no separation at this stage – goes in to the bottom of the spirit still.
The spirit still, with its 16 copper trays, works like a series of mini pot stills in sequence: rising alcohol vapour, hookah-like, bubbles through descending condensate (water and hot feints) held on the trays. Some heavier vapour cools and condenses, while lighter fractions rise up, video game-like, to the next level.
SPIRIT STILL BUBBLE CAPS
The high strength alcohol vapour, taken off at the side of the column, is condensed, and passes to the spirit safe and then spirit receiver tank. The descending condensate trickles down the column from tray to tray, to be reintroduced back to the beginning, at the top of the wash still.
The efficiency of continuous operation is the main advantage over time-consuming, stop-start operation of a pot. Some might add that very high strength distillate being light in aroma, mild in flavour, is too. For at the top of its range, it can be run to distil at 96% abv – technically pure alcohol – lacking any flavour whatsoever, ideal only for vodka, gin etc. The main rule applies: ‘what you put in is what you get out’; poor raw materials in gives poor spirit out; and the higher the strength, the lesser the flavour.
Column stills have had a bad reputation – deservedly so. As distilling purists, what on earth are we doing with one here at Renegade?
It’s certainly not for the economics. The three savings – less fuel, less labour and cheaper raw ingredients – don’t apply to us for we generate our own fuel from bagasse; we have the same distilling team for our pot still as for our column; and we use cane rather than cheap molasses. And we’ve no intention of making inferior quality or flavourless rum, which is why we grow all our own sugar cane.
So why a column still? The answer is perhaps surprising: variety and versatility. We’re not re-inventing the principles of distillation – the main theory being ‘what you put in is what you get out’. Use quality cane-derived wash and you will get good spirit.
COLUMN STILL CAPACITY (MAX)
6,666 LPA Per 24 hours
16 copper bubble caps plates & 8 spirit draw points
19 copper sieve plates
The column still of today is much more refined and complex than ever before. The principals may not have changed since 1830, but the versatility certainly has. With Forsyths, the world’s leading still makers, we have designed a rather special still with 19 copper sieve plates in the wash still, added sacrificial copper contact for purity and, crucially, eight take-off points in the spirit column.
The take-off points are key. This means that different flavour compounds can be separated out – ‘fractions’ of distillate – at differing points up the column: a 70% alcohol will have much greater flavour compared to none at 96%.
But here’s the real trick: we can separate out the desirable flavour elements from the undesirable impurities and discard or reintroduce them back in to the column precisely where we want. It transforms from boring automaton to exciting bespoke still with infinite versatility for flavour. With more precision than a pot still, more variety, more innovation, it’s right up the street of Head Distiller Devon.
One can be more creative these days with a modern column still, particularly if it’s equipped with a few extra enhancements. After all, one can play more tunes on a clarinet than on a recorder.