Whisky or Whiskey comes in many varieties and types – hooray! you may think, after that it all gets a little confusing.
There are two main processes in determining exactly what it is you are drinking, the first is to scour the bottle [and packaging] for any clues. Secondly drink it [assuming it is yours, or you have asked the owners permission first!] but that is another post. The main types of whisky are: malt, grain, bourbon & blend, these can be subcategorised and geographically isolated ad infinitum. Whisk(e)y is the generic name for spirits distilled from grain that are barrel aged. The country of origin is usually stated, often within details of the particular distillery. Whisk(e)y production is growing worldwide and is now produced in Scotland, Ireland, US, Canada, Japan, India, South Africa, Denmark, Finland, Sweden, Germany, Wales, France, Spain, Holland, England, etc.
Malt whisky is made from malted grain (usually barley) distilled in copper pot stills and barrel matured. Single malt must be the product of a single distillery. For it to be Scotch it must spend a minimum of 3 years in a barrel in Scotland, the rest of the maturation can occur elsewhere – even in space [thanks Ardbeg Gallileo].
Grain whisky is made from unmalted barley, maize (corn) and or wheat. Single grain whisky (rare) must be the product of a single distillery, however most grain whisky is produced on industrial scales using a continuous still and is [mostly used] for blending.
Bourbon whisky is a barrel aged distilled spirit made from corn. Traditionally made in the U.S., in particular the southern region of Bourbon County around Kentucky and is usually drank out of a bottle in a brown paper bag [just kidding!! – though this stereotype does have some basis in the fact that it is illegal to be openly seen drinking alcohol in public in some states].
Blended whisky is made by mixing two or more whiskies (be they malt or grain), usually from different distilleries. Traditionally blended scotch contained enough malts to balance it and give it flavour and enough of the cheaper to produce grain whisky to fill out the volume without detracting from the malts. All malt or pure malt blends and all grain blends are possible. Single blend whisky is possible from distilleries that operate both pot and continuous stills, therefore blending their own malt and grain whiskies [e.g. Loch Lomond].
Single cask whisky is exactly what it says – the product of a single cask of matured spirit. Most single malts are actually marriages of numerous casks from the same distillery, often of the same age but occasionally of differing ages and differing finishes to achieve balance in the final whisky [i.e. within malt blends].
Cask strength relates to the alcohol by volume [ABV] percentage. Single malts are usually diluted after maturation, often using the same water source as went into their distillation process. This allows a uniform ABV to be created between batches, ideal for constantly marketed products distributed worldwide subject to numerous legal obligations. Cask strength varies greatly, usually spirit is diluted from the 70-80% ABV out of the still [new make spirit] to around 63% before being interred into the casks for maturation. Around 2% cask volume (mostly alcohol but also a little water) may be lost each year of maturation [called the Angel’s share in Scotland]. So long as the spirit is above 40% ABV at bottling it can be called whisky – tricky if you have cask-matured for 50 years or more for example. The bottle volume and ABV are legal requirements in the UK – likely thanks to the taxman.
Cask finishing relates to the practice of taking whisky from its original cask and adding it to a new cask to take on qualities from that cask. Cask finishing has no pre-defined time, much is done by sampling the whisky regularly at this stage until the desired qualities are achieved. The type of cask used to finish is usually indicated on the bottle, occasionally the exact time spent in the finishing cask may be indicated.
Age displayed on a bottle of whisky relates to the youngest maturation age of any spirit that is in the bottle, usually displayed as minimum X years old. No age statement [NAS] whiskies do not, but you can usually guess they are over 3 years and likely less than the minimum aged expression from the producer [be it 10, 12 15 etc.]. NAS whiskies are often marriages of whisky of different ages – usually these may be indicated somewhere in the blurb on the bottle. Years or dates may be given to show distillation, bottling and occasionally cask transferences for finishing purposes. Marrying of whisky occurs when several casks are mixed together, often at bottling. In some cases numerous casks are married before finishing off in new casks. This again is aimed at batch production, commonly used for staple products e.g. distillery ranges of age statement whisky.
Other information such as Batch number, Year of distillate, Number of bottles at outturn etc. may or may not appear on the label. The more information the better in my opinion!
For the UK legal requirements on labelling scotch whisky see the following: