Americos Chemicals Private Limited Thermochromic Temperature 31ºC Active Heat Sensitive Color Changing Pigment Powder (Violet, 20 g)

I like how it changes from colour to transparent when in contact with heat, but a quick note it won't change colour by just touching or simple sunlight because the minimum temp required is 31 degree and touching or sunlight is not enough. but beautifully changes in contact with a basic lighter or surface of hot tea cup. I like the product but please improve the delivery service.