Irish whiskey is carefully distilled, and produces a clean, refined spirit that matures in the casks into a smooth whiskey. The Irish Whiskey Act of 1980 states that: The spirits have to be distilled in the Republic of Ireland or in Northern Ireland and that the spirits have been matured in wooden casks in a warehouse in the Republic of Ireland or Northern Ireland for a period of no less than 3 years.
Similar to Scotch whisky in many ways, principally in that it was distilled primarily from barley, traditional Irish whiskey was distilled from a mash of mixed malted and unmalted grains (referred to as "pure pot-still" whiskey) whereas Scotch is either distilled exclusively from malted grain (hence "single malt") or from unmalted grain (which is generally then mixed with malt whisky to create "blended whisky"). Today, most Irish whiskey is blended from a mixture of pot still whiskey and cheaper grain whiskey. Bushmills, however, is an exception in that it produces no Irish-style pot-still whiskey.
Most Irish whiskey is distilled three times, but so is some Scotch; thus it is a myth, albeit a common one, that this is the main distinction between the two varieties. Irish whiskey also differs in that peat is almost never used in the malting process, so the smoky, earthy overtones common to Scotches (particularly Islay Scotches) are not present. There are notable exceptions to these "rules" in both countries; an example is Connemara Peated Irish Malt (double distilled) whiskey from the independent Cooley Distillery in Co. Louth.
Although Scotland sustains approximately 90 distilleries, Ireland has only three (although each produces a number of different whiskeys): economic difficulties in the last few centuries have led to a great number of mergers and closures. Currently those distilleries operating in Ireland are: New Midleton Distillery (Jamesons, Powers, Paddy, Midleton, Redbreast, and others, plus the independently sold rarity Green Spot), Old Bushmills Distillery (all Old Bushmills, Black Bush, 1608, Bushmills 10-, 12- and 16- and 21-year-old single malts), and Cooley Distillery (Connemara, Knappogue, Michael Collins, Tyrconnell, and others). Only Cooley's is completely Irish-owned. Irish Distillers' Midleton distillery has been part of the Pernod-Ricard conglomerate since 1988. Bushmills was part of the Irish Distillers group from 1972 until 2005 when it was sold to Diageo.