Mood ring

A mood ring is a ring that contains a thermochromic element, such as liquid crystal, that changes colors based upon the temperature of the finger of the wearer. Most new rings come with a color chart indicating the supposed mood of the wearer based upon the colors indicated on the ring.

The mood ring was created in 1975 by two New York inventors, Josh Reynolds and Maris Ambats, who bonded liquid crystals with quartz stones set into rings. They initially retailed for $45 for a "silvery setting" and $250 for gold, and first sold at Bonwit Teller, rapidly becoming a fad in the 1970s.

A mood ring is a specialized liquid crystal thermometer, wearable on the finger. The ring is typically ornamented with a faux gemstone (usually made of quartz or glass) which is either a clear capsule filled with thermochromic liquid crystal, or has a thin sheet of liquid crystal sealed underneath. Changes in temperature cause the crystal to reflect different wavelengths of light which changes the color of the stone. The liquid crystal used in mood rings is usually set up to display a "neutral" color at the average human skin temperature, which is approximately 37 °C.

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