My prejudice against grain whiskies was seriously shaken recently when I encountered a 39 year old Invergordon grain, from Duncan Taylor.It was in the company of eight malts, all more than 30 years old and to my astonishment the Invergordon was possibly the best of the lot. I could hardly believe it: my snobbish certainty lay in pieces on the floor. It was enough to stir up my interest in grain whisky, and it appears that I am not alone. Some Independent bottlers are responding to (and indeed driving) a swell of interest in single grains.Signatory has recently bottled some 11 year old North British and Cadenheads has a clutch of single grains, including a 19 year old North British, a 10 year old Port Dundas, and a very rare 31 year old Lochside single grain.But Duncan Taylor probably has the biggest range of interesting single grain whiskies, including Invergordon 1965, Port Dundas 1973, Cameronbridge 1979, Carsebridge 1979, North British 1978 and Strathclyde 1973. Even the Scotch Malt Whisky Society has bottled its first single grain: a 13 year old North British and the world’s first organic grain whisky, Da Mhile, is being sold by a farmer in Wales.John Glaser, innovator of Compass Box, says he was “blown away” by a “rich, delicious and approachable” 12 year old Cameronbridge in his Johnnie Walker days and when he set up Compass Box the first whisky he presented to the world was Hedonism: an award-winning vatted grain.John waxes lyrical, almost poetic about grain whiskies, describing them as “the elegant, almost feminine alter ego to Scotland’s malt whiskies” and declares that grain whiskies from good casks are “some of the silkiest, sweetest, most mouth-wateringly delicious whiskies in the world.” Praise and enthusiasm indeed.The big whisky companies certainly value grain whisky as a component in blends. If you speak to blenders they do not see grain whisky as a cheap bulking agent to stretch out the malts. Rather it is a yin and yang partnership with the malt providing the attack, the depth and the spice but the grain providing the softness and consistency.John Ramsey, master blender with the Edrington Group says: “Grain whisky is not as rough as people think – in fact it is the opposite. Grain whisky softens and takes the edge of the malt in a blend”.He proposes the analogy of spaghetti bolognese, in which two components with quite different characters are married together to the mutual benefit of both.But the companies that make grain whisky don’t seem very interested in marketing and selling it. William Grant and Sons produces Black Barrel, which is not available in the United Kingdom, and the 1964 Girvan (now quite rare), Diageo turns out a limited amount of Cameron Bridge, which is very popular in Fife, where it is made. Loch Lomond Distillery is about to launch a Loch Lomond Single Grain, while Whyte & Mackay has withdrawn the ground-breaking Invergordon Single Grain, though it is sold occasionally under the Stillman’s Dram series.Grain whisky is made in a fashion very similar to that of malt whisky: the main difference being that distillation is continuous. The early part of the process is much the same: sugars are teased out of cereals and then fermented to produce an alcoholic ale.In the case of grain whisky the cereal is usually either maize or wheat. Both of these need to be pre-cooked to start breaking down the starches. They are then mixed with a small amount of malted barley which provides the diastase or enzymes which converts the starch into sugar.Thus a porridge of starch is mixed with a slurry of enzymes and the two together are fermented in the usual way in large washbacks. Now comes the interesting bit. The still consists of twin columns, about 40 feet high.Both contain stacked chambers separated by perforated plates. One of the columns also has a worm pipe running through its length. The wash is trickled down the coil pipes of the right hand part of the still (the rectifier).On its way down it is heated by steam. By the time it reaches the bottom it is hot enough to be sent to the top of the left hand part of the still (the analyser) where it flows down, over and through perforated plates. On the way down it once again encounters steam.The rising steam lifts off the alcohol as vapour. The spent wash runs away at the bottom of the analyser but the steam and alcohol vapours go from the top of the analyser back to the bottom of the rectifier.As they rise through the rectifier they meet cold pipes carrying the original wash: this cools the steam and alcohol vapours while preheating the wash (the principle is basically one of heat exchange). The condensing alcohol runs off as spirit roughly three quarters of the way up the column. So all you really need to operate this miraculous piece of equipment is a steady supply of wash and a steady supply of steam. Out comes a steady supply of spirit at around 94.5% ABV.The continuous still might rank as one of the most important technological inventions of the 19th century. It revolutionised the making of whisky, set the conditions for the creation of blends and led to the eventual domination of the world whisky market by Scotch whisky. It also paved the way for the mass production of other spirits, including vodka and gin (most UK-produced gin and vodka is currently made in Scottish grain distilleries) and indeed formed the basis upon which oil refining was eventually developed.It is a startlingly simple idea but must have taken a leap of conceptual genius to think it up.That genius was Robert Stein, member of a renowned distilling family and owner of the Kilbagie distillery in Fife. He came up with the idea of the continuous column still around 1826 and his design was first put to use by his cousin, John Haig, at the nearby Cameronbridge distillery.Stein stills continued to be installed and operated for decades. However, in 1830, a former Inspector General of the Excise, Aeneas Coffey, patented an improved version of Stein’s idea and has gone down in history as the inventor of the continuous still, often referred to, even now, as the Coffey still.Scotland’s first Coffey still was installed at the Grange distillery in Alloa in 1834. Production of patent still whisky in Scotland soared from 231,000 gallons in 1835 to 7,500,000 gallons in 1857. The stills currently operating in Scotland’s seven active grain distilleries have changed little in the basic principles, though in scale and energy efficiency, for example, they have changed enormously.These seven distilleries produce considerably more whisky than all the 100 or so malt distilleries put together. The larger grain distilleries can produce around 70 million litres of whisky a year and even the so-called waste or by-products of spent lees and CO2 can be reclaimed and sold on.The character of grain spirit varies between distilleries in the same way that malt does, either because of the type of grain used or because of process variations, e.g. length of fermentation and of course choice of cask.Grain whisky is not neutral: it has definite flavour characteristics. Remarkably, grain whisky can be enjoyed as new spirit (whisky author Pip Hills believes that is when it is at its best) but it can also benefit from long years in good casks. That makes it pretty versatile and tasting single grain whisky can be challenging. As a rough guide, if you have enjoyed Irish or bourbon whiskies, there is a chance you might enjoy Scotch grain whisky.Michael Jackson said “I have yet to find a single grain that has the complexity of a great malt.” Until recently that would have been my view also, but now I have.The great thing about whisky is its range and diversity. If you exclude the possibility of trying good grain whisky then you narrow the spectrum of possible whisky experiences. Give it a try.