It was the only tasting I have ever attended where half the participants carried weapons. They wore dirks—daggers—either on their belts or thrust into the tops of their knee-length stockings. “This is a sgian dubh,” said the man next to me, drawing his dirk and placing it on the table. “It means ‘black knife’ in Gaelic. The blade was blackened by the peat smoke, you know.”

He was a ghillie laird. Don’t ask me exactly what a ghillie laird is, but he and others belonged to a club devoted to tasting single-malt scotches and they had gathered to sample three vintages from the Macallan distillery. If you think this a casual enterprise, try to pronounce the club’s name, Cuideagh o’ Corn o’ Uisghebeathe (roughly, “tasters of the water of life”).

The ghillie laird had more to tell me, but the bagpipes got in the way. He stood up, smoothed his kilt, and went off for a chunk of smoked salmon. I ate another oatcake to mop off my taste buds, concentrating on the task at hand: evaluating the heady peats before me while keeping a clear head.

The whisky industry is no longer in precipitous decline and sales of single-malt scotch have romped for a couple of decades now. Its popularity reflects the heightened awareness of quality among drinkers of everything from tequila to cognac—and a willingness to pay for it.

“Single-malt,” as virtually everyone knows these days, simply means that the whisky that comes from a single producer. The process enjoys more latitude than you might think, and the results, though they all taste like scotch, are as various as the components: malted barley, peat smoke, in some cases old sherry or bourbon casks, good water, and a certain je ne sais quoi.

According to one Cuideagh o’ Corn o’ Uisghebeathe enthusiast, when the Japanese attempted to assemble their own “scotch” over there, with ingredients—including water—imported from Scotland, they roundly failed.

There are more than a hundred scotch distilleries in Scotland, most of them tiny. The scotch Americans are most familiar with is blended, and comes mostly from the Lowlands. They’re lighter in appearance than single malts, sometimes with caramel color dumped in to make them look “authentic,” and generally taste more or less the same.

On the other hand, single malts, which come from the Highlands and Scotland’s west coast, are highly individualistic. Devotees collect vintages of single malts, and trade them like well-ranked Bordeaux.

Scotch is made from barley that has been germinated in water, kiln-roasted, and subjected to peat smoke in varying degrees. It’s then “mashed” and soaked in water again to liquefy the starches and convert them to sugar, and fermented like beer or wine. The resulting brew goes into a pot still that eventually produces a clear spirit of about 140 proof. Later, spring water is added. The whisky will already bear the taste of the cooking and the peat.

But another palatable element is yet to come, oak, which adds more taste and color. Traditionally scotch was aged in casks that had been used to ship sherry, yielding a lovely symbiosis. The advent of tankers for bulk shipment made sherry casks rarer and more costly, so most scotch found its way into old bourbon barrels brought over from the States. These became the most common cooperage for scotch, but some of the good single-malt distillers still use sherry casks. Producers like Macallan partner with Spanish sherry houses that supply them with staves imbued with the taste of Amontillado and Oloroso.

Which brings me back to the glasses lined up before me. In addition to the three Macallan vintages—aged 12, 18, and 25 years—a fourth glass contains a 10-year-old Glenmorangie, one of Scotland’s most popular single malts.

I learned that the way to smell any strong spirit is to pass the glass under your nose twice at most. The Macallans were “lightly peated” and lacked the oily quality of heavier single malts made in the west of Scotland, which I discovered on a trip to the inner Hebrides and will write about another time.

Single malts produced by Lagavulin and Laphroaig, neighbor distilleries on the isle of Islay (pronounced “Eye-lay”), smell vaguely of tea and iodine derived from the vast ocean on their doorsteps. The older ones are a deep amber, with a sweetish, complex nose. A more lightly peated—and less expensive—single-malt from Islay is Bowmore.

Finally, single malts taste better with a dollop of (un-chlorinated!) water. And forget about an ice cube if you find yourself in the presence of a single-malt partisan wearing a sgian dubh.

Featured contributor James Conaway writes for National Geographic Traveler and other publications devoted to travel, history, and culture. Read more from James on his wine blog.