Tempil incorporates state of the art temperature indicator technology to develop a wide range of temperature measurement
products which include temperature indicators, temperature strips, temperature labels, temperature dots, and sterilization inks.
These products are produced in a wide range of configurations to meet the needs of applications requiring accurate
temperature measurement and temperature control. Common usage includes sterilization processes, pharmaceutical
packaging, temperature testing, temperature measurement and temperature verification.

Below is a very interesting temperature guide for ferrous metals, submitted by a blacksmith friend and produced by Tempil. 
The image is a large jpeg file that takes time to load, be patient, its worth it: