The Science Behind Mood Rings

The mood ring was invented in 1975 by Joshua Reynolds, a marketing executive from New York City, and experienced fad popularity in the 70s, with the stone in the ring changing colour, supposedly according to the mood or emotional state of the wearer being a fascinating concept. Even today, they are still around, with mood rings, necklaces and bracelets all holding a permanent spot in the jewellery market. 

Mood ring colour chart

Of course, the mood rings cannot relay your actual emotional state with any degree of accuracy (since they possess no psychic abilities!) but the science behind the colour changing stone can be scientifically explained.

The ‘gem’ or ‘stone’ in the ring is really a hollow shell or quartz or glass encasing thermochromic (undergoes a reversible change in colour when heated or cooled) liquid crystals. The metal band of the mood rings conducts heat from the finger to the liquid crystal, which changes colour in response to the temperature of the skin. There are several natural and synthetic crystals that possess these temperature-sensitive properties, but the most common organic polymer used to make the crystals is based on cholesterol. More energy is available to the crystals as the ring becomes warmer; the molecules absorb the energy and twist which affects the way light passes through them. This means that the wavelengths of light that are absorbed or reflected by the ‘stone’ are affected.

The crystals are calibrated to reflect colours that are associated with certain moods; for instance, they are manipulated to reflect and therefore display a pleasing blue/green colour at the average resting peripheral temperature of 37.5ᵒc – implying the wearer is calm and relaxed. External body temperature increases in response to emotions of passion and happiness, and the crystals twist to reflect more blue light as they respond to the thermal change.  This is called the nematic phase; it is characterised by the rod-shaped crystal molecules pointing in the same directions but without any specific order. When the wearer is excited or stressed, blood flow is directed away from the skin to vital organs which require the excess glucose and oxygen to function in this state. For instance, when in a stressful situation the body goes into a ‘fight or flight’ response that triggers numerous hormonal changes. In the heart for example, the extra adrenaline binds the heart causing it to beat faster and pump a higher volume of blood quickly. This diversion of blood flow leaves the fingers cooler, causing the crystals to twist in the opposite direction, to reflect more yellow light, creating the red and amber colours. This is the cooler smectic phase, when the crystal components are aligned and display a degree of order.  

So, although mood rings do not have the psychic power to reflect what mood you’re in, the composition of the crystals does give the ‘gem’ the ability to respond to changes in body temperature… which to a certain extent can be related back to the emotional state of the wearer. Kind of cool really! 

References:
https://www.thoughtco.com/mood-rings-thermochromic-liquid-crystals-608013