Somewhere in the mash of an Irish pot still whiskey there is barley that was never allowed to germinate. Raw grain, hard and starchy, the kind no malt distiller in Scotland would touch. It goes in alongside malted barley, and that mixture is the category. The usual explanation is tax: for much of the nineteenth century malt was what the exchequer counted. Whether that is the whole reason or a story told afterwards, the effect is not disputed. Unmalted barley makes a heavier, greener, more peppery spirit. Ireland kept it after the tax was gone.
The other thing Ireland had, and gave away, was the still that made everything after it possible. Aeneas Coffey was an Irish excise officer who patented a continuous still in 1830. It ran without stopping, took cheaper grain, and worked at a scale no pot still can reach. The Dublin houses looked at it and said no. Their objection was that what came out was not whiskey, and by their definition they were right. Scotch blenders bought it anyway, married that grain spirit to malt, and built the modern industry on the join. The Dublin houses were right about what came out of the column, and it made no difference at all to what happened next.
Triple distillation is the other habit, and it is worth being exact about it. A third pass is not a third helping of the same thing. Every trip through copper strips sulphur from the vapour. Every trip raises strength, which lets the distiller cut harder and throw more away. What comes off the third still is lighter and further from the grain it started as. The gain is entirely in what is missing. Scotland triple distils in places, Auchentoshan among them, and plenty of Irish whiskey is distilled twice. Ireland has a preference consistent enough that people read it as a rule. Nothing in the definition of Irish whiskey requires it.
The collapse took about fifty years and had no single cause, which is why it is usually told badly. Independence and a trade war closed Britain and its empire. Prohibition closed America, and when it opened again much of the whiskey with Irish names had never been near Ireland. Scotch spent those decades building blends and distribution. Irish whiskey came back to a market that had learned to ask for something else. The distilleries closed one at a time, then in groups.
In 1966 the three big surviving firms merged into one company, Irish Distillers. Bushmills followed a few years later, and by the end of the 1970s almost all Irish whiskey came from two places, in County Cork and County Antrim. What carried the old names through was not a distillery. It was the bonding trade, where a merchant bought new spirit by the cask and matured it under his name. The story behind Green Spot is a Dublin firm marking casks with paint to keep the ages straight. Redbreast came out of the same trade.
Distilling came back to Dublin in 2015. Teeling opened in a city that made whiskey for centuries and then made none for decades. Cooley had gone first, in 1987, in a converted plant on the Louth coast. The malt it is known for, Connemara, is peated, which almost nothing else in Ireland is. The number of working distilleries on the island has been climbing long enough that any count printed here would only date the page.
Texture is what settles the argument. Single pot still sits heavier than a malt of the same age, oilier across the middle, with a green peppery edge the cask never quite covers. That weight is what the unmalted barley leaves behind, kept by a country that had every commercial reason to drop it and did not.