A mood ring is a ring which contains a thermochromic

Thermochromism

Thermochromism is the ability of substance to change color due to a change in temperature. A mood ring is an excellent example of this, but it has many other uses such as baby bottles and kettles. Thermochromism is one of several types of chromism.The two basic approaches are based on liquid...

 element, such as liquid crystal

Liquid crystal

Liquid crystals are a state of matter that have properties between those of a conventional liquid and those of a solid crystal. For instance, an LC may flow like a liquid, but its molecules may be oriented in a crystal-like way. There are many different types of LC phases, which can be...

. The ring changes color in response to the body temperature of its wearer. The color is said, by some proponents, to indicate the emotional state

Emotion

Emotion is a complex psychophysiological experience of an individual's state of mind as interacting with biochemical and environmental influences. In humans, emotion fundamentally involves "physiological arousal, expressive behaviors, and conscious experience." Emotion is associated with mood,...

 of the wearer.

History

The mood ring was invented 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

Bonwit Teller

Bonwit Teller was a department store in New York City founded by Paul Bonwit in 1895 at Sixth Avenue and 18th Street. In 1897 Edmund D. Teller was admitted to the partnership and the store moved to 23rd Street, East of Sixth Avenue...

, rapidly becoming a fad in the 1970s.

Function

A mood ring is a specialized liquid crystal thermometer

Liquid crystal thermometer

A liquid crystal thermometer or plastic strip thermometer is a type of thermometer that contains heat-sensitive liquid crystals in a plastic strip that change color to indicate different temperatures....

, wearable on the finger. The ring is typically ornamented with a faux

Fake

Fake means not real.Fake may also refer to:In music:* Fake , a Swedish synthpop band active in the 1980s*Fake?, a Japanese rock band* Fake , 2010 song by Ai featuring Namie Amuro...

 gemstone

Gemstone

A gemstone or gem is a piece of mineral, which, in cut and polished form, is used to make jewelry or other adornments...

 (usually made of quartz

Quartz

Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...

 or glass

Glass

Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

) which is either a clear capsule filled with thermochromic liquid crystal

Liquid crystal

Liquid crystals are a state of matter that have properties between those of a conventional liquid and those of a solid crystal. For instance, an LC may flow like a liquid, but its molecules may be oriented in a crystal-like way. There are many different types of LC phases, which can be...

, 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 98.6 °F (37 °C).

The theory behind the idea that the ring indicates the wearer's mood is based on a claim that body heat

Body heat

Body Heat is a 1981 film by Lawrence Kasdan.Body Heat may also refer to:*Body heat or thermoregulation, the ability of an organism to keep its body temperature within certain boundaries*Body Heat...

 fluctuates with the emotional state of the wearer. Human body temperatures are known to vary by small amounts (less than 5°C) over the circadian and menstrual cycles and when the body is fighting an infection. Variations in ambient air temperature appear to have a larger effect on the temperature of the ring than changes in the body temperature of the wearer. It appears that no direct correspondence between a particular mood and a specific color has ever been substantiated.

In popular culture

Mood rings were a short-lived fad of the mid-1970s (like the pet rock

Pet rock

Pet Rocks were a 1970s fad conceived in Los Gatos, California by advertising executive Gary Dahl.-Development:In April 1975, Dahl was in a bar listening to his friends complain about their pets. This gave him the idea for the perfect "pet": a rock...

) and were especially popular with young girls. In a 1976 Peanuts

Peanuts

Peanuts is a syndicated daily and Sunday American comic strip written and illustrated by Charles M. Schulz, which ran from October 2, 1950, to February 13, 2000, continuing in reruns afterward...

comic strip, Peppermint Patty

Peppermint Patty

Patricia "Peppermint Patty" Reichardt is a fictional character featured in Charles M. Schulz's comic strip Peanuts. A freckle-faced auburn/brunette, she is one of a small group in the strip who lives across town from Charlie Brown and his school friends...

 gets so angry at Charlie Brown

Charlie Brown

Charles "Charlie" Brown is the protagonist in the comic strip Peanuts by Charles M. Schulz.Charlie Brown and his creator have a common connection in that they are both the sons of barbers, but whereas Schulz's work is described as the "most shining example of the American success story", Charlie...

that her mood ring explodes.