Abstract: A temperature indicator includes a transparent substrate with a first code and a second code disposed on a first side of the transparent substrate. The first code comprises a first color and the second code comprises a second color different than the first color. An absorbent medium is disposed on a second side of the transparent substrate opposite the first side and comprises a third color that contrasts with only the second color of the first and second colors. A substance is disposed between the absorbent medium and the transparent substrate. The substance comprises a fourth color that contrasts with only the first color of the first and second colors and is meltable and absorbed by the absorbent medium in response to a temperature exceeding a temperature threshold.