Thermochromic Pencils

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Get similar pencils here: Thermochromic Pencils

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Themochromic Pencils: some amazing pencils I found in the @exploratorium gift shop last week that exhibit reversible color change. The warm air from a hair dryer can quickly shift the color of these pencils, and then as they cool back to room temperature the original color slowly fades back in. The color change can also be achieved by body heat from the hand (swipe for demo). The color change seen here most likely employs leuco dyes, thermochromic chemicals that have two reversible forms, one colorless when warmed above a threshold temperature.

Cherry Blossom Thermochromic Sake Cups

Similar cups available here- some change with hot water, some with cold:

From Amazon: BUY NOW: Cherry Blossom Color Change Cup

Check out these other thermochomic physics toys

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Cherry Blossom Sake Cups: ice cold liquid produces blue blossoms on the initially bare branch, but pour in a hot beverage and the branch fills with pink flowers! The designs at the bottom of these ceramic color-changing cups employ leuco dyes, thermochromic chemicals that have reversible forms, one colorless.

Thermochromic Safety Sticker

These stickers transition back and forth and can be used on many surfaces. Get some here:

From Etsy: BUY NOW: Thermochromic Saftey Sticker

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Thermochromic Safety Sticker: the liquid crystal ester dye in this reusable sticker is calibrated to change color when the surface temperature exceeds 50°C (122°F)- that at which prolonged contact (more than 0.5s) will burn skin. Here the safety sticker is attached to a slab of aluminum and heated with a simple candle- it took about 3.5 minutes for the heat to distribute and bring the aluminum to the threshold temperature. When the surface cools the sticker again appears blank and can transition over and over again


Thermochromic Eclipse Postage Stamps

Available from the US Post Office and here: 
From Amazon: BUY NOW Thermochromic Eclipse Stamps 

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Thermocromic Eclipse Postage Stamps: In commemoration of the 2017 total solar eclipse the US Post Office released their first ever stamp featuring thermocromic ink. The first physics toy stamp! Thermotropic liquid crystals go from opaque to transparent during a phase change from a crystal to liquid state. Here the warmth of the hand reveals the face of the moon in front of the solar corona. Almost seven years later another total eclipse will take place across part of the US on April 8- I’ll be in San Antonio for the event! 

Thermochromic Liquid Crystal Mood Necklace

Similar mood jewelry available here: 
From Etsy: BUY NOW Liquid crystal jewelry

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Thermochromic Liquid Crystal “Mood” Necklace: heat from a hand brings out the temperature dependent color change of the liquid crystal. The molecules of the liquid crystal change orientation and spacing during the phase transition from liquid (warm) to crystal (cool). The molecular configuration shift allows for different diffraction effects producing the color shift. 

Thermochromic Chiral Liquid Crystals

Available here: 
Liquid crystal sheets, thermochromic fun!: 
From Educational Innovations: BUY NOW liquid crystal thermometer sheet 

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Thermochromic Chiral Liquid Crystals: the thin layer changes color as the molecules of the liquid crystal change orientation and spacing during the phase transition from liquid (warm) to crystal (cool). 


Thermochromic Beam Down Mug

Get one here: 
From Amazon: BUY NOW Beam Down Star Trek Mug 

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Thermochromic Beam Down Mug: Pour up some hot coffee and watch the crew of the USS Enterprise leave the ship and rematerialize on the planet surface with this color-changing physics mug. The color change employs leuco dyes, thermochromic chemicals that have two reversible forms, one colorless when wqrmed above a theshold temperature.