Thermochromic Spoon

This plastic-coated stainless steel baby spoon is thermochromic: the 'soft-bite' plastic head changes colour from green to white when the temperature of the food or drink it comes in contact with exceeds 43ºC, and changes back to green again when it cools down. This is possible because the soft plastic coating (most likely PVC) contains a thermochromic additive that gives it its green colour. When the spoon is dipped in a hot jar of baby food, the thermochromic pigment in the plastic will turn transparent so that the white of the plastic matrix material shows through. The base of the spoon is metal because it conducts heat well, making the spoon very reactive to hot substances. It also stores heat, lengthening the colour change response of the plastic to the hot food and making it more noticeable.