Tears of Wine: Why Your Glass Grows Climbing Drops (Field Guide)

You swirl a glass, and suddenly tiny droplets climb upward, gather, then fall.

That “wine legs” effect is not magic and not quality scoring — it is a beautiful surface-tension-driven flow instability.

1) One-sentence intuition

Ethanol evaporates faster than water, creating surface-tension gradients that pull liquid up the glass; gravity then wins locally, so droplets detach and fall as repeating “tears.”

2) Minimal mechanism (what must happen)

In the thin film near the glass wall:

1. Capillary action lifts wine up the wall.
2. Ethanol evaporates faster than water.
3. Local ethanol depletion raises surface tension.
4. Surface-tension gradient (Marangoni stress) pulls more liquid upward.
5. A ridge forms near the top of the film.
6. The ridge destabilizes into droplets that fall under gravity.

Repeat this loop and you get the familiar “legs/tears/church windows.”

3) Why ethanol-water mixtures are special

The effect depends on thermodynamics, not vibes:

• Ethanol lowers surface tension versus water.
• Ethanol has higher vapor pressure, so it evaporates preferentially.
• That evaporation continuously regenerates concentration gradients.

So the film is never truly static: composition keeps drifting, and flow keeps re-driven.

4) The 2015 update people often miss: temperature also matters

Classic explanations focused mostly on composition gradients.

Venerus & Nieto Simavilla (2015, Scientific Reports) used IR thermography + hydrodynamic modeling and showed:

• evaporative cooling creates a measurable temperature gradient along the film,
• and thermal Marangoni contribution can be comparable in magnitude to concentration-driven contribution for typical wine mixtures.

Reported order-of-magnitude values in their analysis include:

• film thickness scale ~30 μm,
• film height scale ~10 mm,
• temperature gradient around (T' \sim -100,\mathrm{K/m}) (wine case).

Takeaway: tears are typically composition + thermal Marangoni, not composition-only.

5) Why droplets appear regularly instead of random drips

The upper film/ridge behaves like a thin-film hydrodynamic instability problem.

So “tears” are not arbitrary splashes; they emerge from patterned instability and wave dynamics in the climbing film.

More recent theory (Dukler et al., 2019/2020) frames parts of the phenomenon with undercompressive shock-wave structures in thin-film equations, offering a modern language for why coherent wave fronts can precede breakup into tears.

6) Fast myth busting

• “More legs = better wine.”
  Not reliable. Legs mainly reflect evaporation/surface-tension dynamics (especially alcohol effects), not direct quality.

• “Legs mean sweeter wine.”
  Not a dependable rule.

• “It’s viscosity alone.”
  Viscosity affects details, but the core driver is Marangoni stress from evaporation-induced gradients.

• “If you stop swirling, it should stop instantly.”
  Not necessarily; gradients and film dynamics can persist for minutes.

7) Tiny home experiment

1. Use two clear glasses: one open, one loosely covered.
2. Put same wine (or ethanol-water mix) in both.
3. Swirl similarly and wait.
4. Compare tear formation.

Expected trend: covering suppresses evaporation, weakening gradients and reducing tears.

(Do this as a qualitative demo, not precision measurement.)

8) Why this is a useful systems metaphor

Tears of wine are a compact lesson in nonlinear systems:

• A gradient creates flow.
• The flow reshapes the gradient source.
• Instability creates structured, repeating events.

That loop appears everywhere: coating flows, microfluidics, heat/mass transfer devices, and many “why is this oscillating?” engineering headaches.

9) References (starter set)

• Thomson, J. (1855). On certain curious motions observable at the surfaces of wine and other alcoholic liquors. Philosophical Magazine.
• Marangoni, C. (1865). Sull'espansione delle gocce di un liquido galleggianti sulla superficie di altro liquido.
• Venerus, D. C., & Nieto Simavilla, D. (2015). Tears of wine: new insights on an old phenomenon. Scientific Reports, 5, 16162. https://doi.org/10.1038/srep16162
• Dukler, Y., Ji, H., Falcon, C., & Bertozzi, A. (2020). Theory for undercompressive shocks in tears of wine. Physical Review Fluids, 5, 034002. (arXiv preprint: https://arxiv.org/abs/1909.09898)

If useful next, I can make a compact “kitchen-lab protocol” with variables to log (ABV, glass angle, humidity, cover/no-cover, tear spacing/frequency) so this becomes a mini reproducible fluid-dynamics experiment.