Walk into a specialist shop and you'll find glasses designed for specific grape varieties, sold with explanations about how the bowl shape directs wine onto particular parts of the tongue.

That specific explanation is definitely wrong. The tongue map — sweet at the tip, bitter at the back — was debunked decades ago; taste receptors for all basic tastes are distributed across the tongue. Any glass marketing that relies on it is selling you something on a false premise.

But the glasses aren't entirely nonsense either, and it's worth separating the real effects from the invented ones.

What genuinely matters

Size and headspace. The biggest real effect. A glass with a large bowl, filled to about a third, has a substantial volume of air above the wine in which aroma compounds accumulate. A small glass filled to the brim has almost none.

Since most of what we call taste is actually retronasal smell, concentrating aroma in the headspace makes a genuine difference to perceived intensity. This is not marketing, it's just physics, and it's why a decent large glass improves nearly any wine.

A rim narrower than the bowl. Tapering concentrates the accumulated aromas towards your nose rather than letting them disperse. Again, straightforwardly physical.

Thin rim. A thick, rolled rim changes the way wine enters your mouth and is genuinely noticeable. Thin rims deliver the wine more cleanly. This is a real and slightly surprising difference.

Clear, plain glass. Coloured or heavily cut glass prevents you seeing the wine, which affects perception considerably given how much of taste is visual expectation.

A stem, or at least somewhere to hold it. Not aesthetics. Holding the bowl warms the wine measurably, and hand warmth on a white wine will take it out of its ideal range within minutes.

What matters less than claimed

Variety-specific shapes. The differences between a Cabernet glass and a Pinot glass are real in the sense that the shapes differ, and the effect is much smaller than the pricing implies.

The general principle — bigger, rounder glasses for aromatic delicate reds; slightly narrower for tannic powerful ones — has a logic to it. Whether it justifies owning eight different sets is a different question, and I'd say clearly not for almost everyone.

Champagne flutes. Here's a case where the traditional glass is actively worse. The flute was designed to show off bubbles and it does that well. It also has minimal headspace and a narrow bowl, which suppresses aroma almost completely.

Good Champagne is a complex wine and a flute hides most of it. A standard white wine glass is better, and most people in the trade have quietly switched. You lose some of the visual display of the mousse, which is a fair trade.

Extremely expensive crystal. Lead-free crystal is thinner and more elegant than standard glass and it's nicer to drink from. Whether it changes the wine perceptibly is much less clear, and blind comparisons of high-end glassware have not produced consistent results.

The decanting question

Adjacent topic that comes up constantly. Two separate reasons to decant and they're often conflated.

To remove sediment. Older reds throw a deposit. Pouring carefully off the sediment into another vessel is straightforwardly useful and requires no aeration at all — in fact you want minimal aeration with a fragile old wine.

To aerate. Young tannic reds can soften with oxygen exposure. This is real but modest, and an hour in a decanter does considerably more than swirling in a glass.

The confusion causes actual harm: people vigorously decant a delicate forty-year-old wine, which can collapse within twenty minutes of air exposure, and gently decant a young Barolo that needed three hours.

Rule of thumb: young and tannic, decant early and vigorously. Old and fragile, decant carefully just before serving, or not at all.

Temperature, which matters more than any glass

The single biggest improvement available to most people's wine drinking, and it costs nothing.

Most white wine is served far too cold, straight from a fridge at four or five degrees, which suppresses aroma almost entirely. Ten to twelve is better for anything with complexity.

Most red wine is served too warm. "Room temperature" is a phrase from an era of unheated houses. Modern room temperature of 21 degrees or more makes reds taste alcoholic and flabby. Sixteen to eighteen is right for full reds, and lighter reds are excellent at around fourteen — genuinely worth chilling.

If you did nothing else, taking reds out of the room for twenty minutes in the fridge and whites out of the fridge for twenty minutes before serving would improve your drinking more than any glassware purchase.

What I'd buy

One set of decent, large, thin-rimmed, plain glasses, used for everything including Champagne. Something in the 450 to 600 millilitre range.

They'll be better than 90% of what you'd get from an elaborate variety-specific collection, they cost a fraction, and you won't have to think about which one to use. Which is worth something on a Tuesday evening.