Scotch whisky produced from pure
malted barley rather than being
blended from a mix of malt whisky and grain whisky. Note that this is distinguished from
whiskey, which is irish, and
bourbon, which is american.
Nowadays, most malt whiskys are single malts - that is, they are made from malt from a single distillery, rather than being mixed from the produce of several distilleries. Other malt whiskies are known as vatted malts, and include such brands as Scottish Pride, Sheep Dip, and Poit Dhubh.
Apart from the brand (normally the name of the distillery that made the whisky), single malts are often distinguished along the following axis:
- Age.
Whisky is aged in barrels to aquire the taste; usually from 10 to 21 years. Usually, it is better the longer it has aged, but this is not universal. Aging stops when the whisky is bottled, so sitting in the cupboard since your father's college days do not count. The minimum aging for a scotch whisky (in order to be legally branded as Scotch) is 3 years, which (of course) has to happen in Scotland, and in oak casks.
- Normal vs cask strength.
Whisky is normally watered out after having aged, bringing it down from its original 51% to 65% by volume to a measly 40% to 43%. In a cask strength, this has not been done, and the taste is much stronger. It is common to add a small dash of water to a drink of cask strength, in order to release more of the taste.
- Single vs double wood.
Whisky is normally aged in a single barrell. However, some special variants are instead aged in two different barrels, in order to obtain a deeper, rounder taste. These are normally known as "Double Woods"; I can especially recommend the 18 year old Lagavulin Double Wood.
- Mixed vs single cask vs Founder's Reserve.
Normally, whisky is made by mixing up most of the barrels from the year, giving a uniform quality for that year. However, it is also fairly common to pick out the best barrels from the year, bottling each of these separately, and selling them as Single Cask. The whisky bottled from the single best barrel of the year is often known as Founder's Reserve. (Note that this term has also been used as generic branding, and do not enjoy any special protection, so be sure to check that you are getting what you expect.)
- Type of barrells used.
Whisky is usually aged in used brandy barrells, or barrells made especially for the purpose. However, there are also available whiskies that have been aged in other types of barrells - for instance, Glenmorangie is available in normal (aged in bourbon casks), Port wood, Madeira wood, and Sherry wood finishes.
- Double vs triple distilled.
The common scottish whisky is distilled twice; the common irish whiskey is triple-distilled. However, there are some scottish whiskies that are triple-distillated - Auchentoshan, Benrinnes and Rosebank, to be exact.
If you want to make the bartender (and, after you get it, yourself) happy, ask for your malt whisky in a cognac glass. If you feel like asking for ice in that, I think you'd be more happy drinking something else - you are probably really looking for a blended whisky, not a malt.