Thermochromic ink and document printed therewith

A document, comprising:

• a substrate;
• and
• a coating disposed as a uniform layer on an area of said substrate, said coating including a first thermochromic material that appears as a first color when it is below a first temperature and that appears substantially transparent when it is above said first temperature, said coating including a second thermochromic material that appears as a second color when it is below a second temperature and that appears substantially transparent when it is above said second temperature, said coating including a third thermochromic material that appears as a third color when it is below a third temperature and that appears substantially transparent when it is above said third temperature, said second temperature being higher than said first temperature and said third temperature being higher than said second temperature, whereby said coating disposed on said area of said substrate appears as a fourth color which is a mixture of said first, second, and third colors when said coating is at a temperature that is less than said first temperature, said coating disposed on said area of said substrate appears as a fifth color which is a mixture of said second and third colors when said coating is at a temperature that is less than said second temperature and greater than said first temperature, said coating disposed on said area of said substrate appears as said third color when said coating is at a temperature that is less than said third temperature and greater than said second temperature, and said coating disposed on said area of said substrate appears as the color of said substrate when said coating is at a temperature that is greater than said third temperature.