Phosphors are fine white powders which fluoresce when suitably excited. Many of them are ceramics and can withstand extremely high temperatures.  

The fluorescence characteristics change with temperature and thus a phosphor coating may indicate the temperature of the surface onto which it is coated. Seen here is a tensile specimen coated with phosphor and illuminated with a black light so that the stripes of phosphor glow red.

There are a wide variety of ceramic phosphors which fit these characteristics:

	Survives hazardous chemical environments.
	Not water soluble.
	Durable.
	Easy to apply.

The white stripes of phosphor on this metal specimen glow red when illuminated by a black light. Some phosphors have no trouble surviving and functioning in high temperatures such as those produced by this propane torch.