Temperature Marker 413 F

Designed to work with no-clean paste (Sn63/Pb37).
Before placing the PCB in the oven cut a piece of the Temperature Marker with a blade or a sharp knife and place it on the surface of the board next to a large component (PLCC or QFP). Make sure you can see the Temperature Marker material through the oven door. The Temperature Marker material is opaque initially but when 413 °F (212 °C) is reached the material liquifies and becomes shiny, non-reversibly.