You may have noticed it before: when you gently swirl your glass of wine, thin streaks or small tears slowly run down the inside of the glass. These so-called church windows – also known as wine legs or wine tears – are not just beautiful to look at, they also tell you a bit about the alcohol, sugar and extract content of your wine.

• Church windows, tears, legs and streaks as synonyms
• Indicate alcohol, sugar and extract concentration
• Rule of thumb: more streaks usually mean higher alcohol
• They do not indicate wine quality

When the wine “cries”

These so-called tears appear when you swirl your glass. As the wine coats the inside, the liquid climbs up slightly and then slowly runs back down in thin trails – just like tiny rivulets. This fascinating effect can be explained by physics: the Marangoni effect.

The Marangoni Effect explained

Named after the Italian physicist Carlo Marangoni, this effect describes how liquids with different surface tension behave. Alcohol evaporates faster than water, increasing surface tension along the glass. The upper film then pulls wine from lower layers upward until it becomes too heavy and flows back down as small “tears.” The higher the alcohol or sugar content, the more pronounced this effect becomes.

In the past, people believed that glycerol (a byproduct of fermentation) caused these tears because it affects viscosity. Today, we know that glycerol has very little influence – it’s the physical interaction between alcohol and water that creates the phenomenon.

What wine tears actually tell you

Rule of thumb: The narrower and denser the tears, the higher the wine’s alcohol and extract levels. Broader, slower “legs” usually indicate lighter wines with less alcohol or sugar. If you barely see any, you’re likely holding a light-bodied, low-alcohol wine.

Conclusion: Beautiful, but not a sign of quality

Church windows are a lovely visual detail, but they are not an indicator of quality. The appearance depends on glass shape, temperature, and sugar levels. So next time you swirl your wine – just enjoy the view, and focus on what really matters: how it tastes.

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Photo credits: @marcelgross.ch via Unsplash

Frequently Asked Questions (FAQ)

What are church windows or wine legs?

They are the streaks or “tears” that form inside the glass after swirling. They result from differences in surface tension between alcohol and water.

Do wine tears indicate wine quality?

No, they only reflect alcohol, sugar, or extract levels – not quality, balance, or complexity.

When are wine legs most visible?

They appear most clearly in wines with higher alcohol or sugar content, at room temperature, and in clean, dry glasses.

Which wines show strong church windows?

Full-bodied red wines, sweet dessert wines, and fortified wines often display pronounced “legs” due to their higher alcohol or sugar content.