Irish Coffee is not Irish whiskey. Let's make that perfectly clear.
Let's look at the birthing process of a bottle of Bushmills Irish Whiskey. It starts with barley. The barley is allowed to sprout, a process called malting, and then dried in closed ovens, called kilns. Our barley is now not just ordinary barley, but malted barley. Whiskey that is made from 100% malted barley is referred to as malt whiskey.
Next, our malted barley has a rather unpleasant (for the barley) thing done to it. It is ground into a coarse flour called grist, and then, to add insult to injury, it is mixed with warm water in a huge vessel, which is located in the brewhouse. As this mixture is stirred, an enzyme in the malt (the malted barley) transforms the starch in the barley into fermentable sugars. After three hours of this, all of the starches in the barley have been dissolved in the water, and transformed into sugars. This sugary liquid, known as wort, is now pumped from the brewhouse to the fermentation vats.
The fermentation vats contain yeast, which, upon contact with the wort, begin transforming the sugars in the wort into alcohol. It takes about two days for all of the sugars to ferment, and the wort slowly becomes a liquid called wash. At this point, the wash is about 8.5% alcohol. Off it goes to the still house, hooray!
In the still house, the wash is distilled, so as to separate the water and alcohol. The Pot Still, which is a giant copper kettle, is filled with wash, and brought to a boil. Over time, the highest and most volatile members of the alcohol family start to rise as steam in the neck of the still, and pass to the condensers, where they are condensed into liquid. This liquid goes back into the Pot Still for the next stage of distillation.
Bushmillsis unique, in that it is triple distilled. The condensed product from the first distillation is called low wine, the second is called feints, and the third, spirit. Spirit is approximately 80% alcohol by volume, or 160 proof. In each stage of distillation, good elements in the whiskey are separated from undesirable elements, giving Bushmills an exceptionally smooth flavor. For comparison's sake, Scots whisky and bourbon are both distilled twice.
Now the whiskey has to age, where it is stored for a number of years in oak casks while the flavor of the whiskey mellows. By law, all Irish whiskey must be aged for at least 3 years. Bushmills distillery uses three types of casks: Oloroso sherry butts, American oak bourbon barrels and port wine pipes. These casks have already had the strongest tannins and oak extracts leached out of them, by the previous inhabitants, leaving the wood in perfect condition for maturing Irish whiskey.
Finally, the mature whiskeys are taken from the warehouse and pumped into vats. These whiskeys are then blended according to a precise formula, based on the brand of Bushmills that is desired. This process is referred to as vatting, rather than blending, to distinguish it from the blending process used in making Scots whisky. The distinctive flavor of each Bushmills product is primarily achieved by the distilling and maturation process, rather than the blending process, as in Scots whisky.
Finally, the whiskey is reduced with water to exactly 40% alcohol by volume, and bottled for distribution.