When the rim of a crystal wine glass is rubbed with a wet finger, it vibrates at a resonant frequency and produces a musical tone. This experiment investigates how the shape of a wine glass and the amount of liquid it contains influence the pitch of the sound produced.

1. Choose one crystal wine glass and inspect it for chips or cracks.
2. Measure the total volume the glass can hold using a graduated cylinder or scale.
3. Dry the outside of the glass and place it on a stable, non-slip surface away from electronics.
4. Wet your fingertip with clean water and lightly rub along the rim to start the tone.
5. Once the tone is steady, observe and record the pitch using a tuner app or frequency analyzer.
6. Add a measured amount of water to the same glass, gently swirl to settle, and repeat the rub-and-measure step.
7. Continue with several added amounts, recording the pitch after each fill.
8. Compare how the pitch changes as the water level rises in the same glass and summarize the pattern you observe.

Science at Home - SE1 - EP8: Physics of Sound - Part 1: Singing Wine Glass - The Sci Guys:

Resonating wine glasses - Keith Gibbs:

📄 Resonance in a Crystal Glass - Casey Riscoe, Hope Titus, Mary Bywater, Matthew Taylor: https://tuhsphysics.ttsd.k12.or.us/Research/IB11/RiscTituBywaTayl/index.htm

• Test specific fractional fills of the same glass (such as eighths, quarters, halves) and compare the pitch at each level.
• Repeat the sequence after gently warming or cooling the water to see if temperature changes affect the tone.
• Replace water with a thicker liquid (for example, sugar solution) to examine how viscosity influences the sound.
• Record with a microphone and visualize the waveform and spectrum to look for overtones and shifts in resonance.

• Handle the crystal glass carefully; do not press hard on the rim to avoid cracking.
• Keep liquids away from laptops, outlets, and power cords; use a splash-safe setup.
• Clean up spills immediately to prevent slips and protect equipment.

• Why does adding liquid to the glass tend to lower the pitch? (The added mass and fluid motion dampen the rim’s vibration, reducing the resonant frequency.)
• What properties of crystal help it “sing” more clearly than ordinary glass? (Its composition and structure allow stronger, longer-lasting vibrations with less internal damping.)
• How might glass thickness and rim shape influence the tone quality? (They change stiffness and damping, which alter both pitch and sustain.)
• Why are additional tones sometimes heard besides the main pitch? (Overtones arise from different vibration modes of the rim and interactions with the liquid and air.)