Humidity indicator

Humidity and hygrometry
Specific concepts
	Absolute / Specific / Relative; Dew point (depression); Psychrometrics;
General concepts
	Air; Concentration; Density; Dew; Evaporation; Humidity buffering(Atm.) Pressure; Liquid water; Avogadro's law; Nucleation; Thermodynamic equilibrium;
Measures and Instruments
	Heat index; Sat. vap. density; Mixing ratio; Water activity; H. indicator card; ; Hygrometer; Dry/Wet-bulb temperature;

A humidity indicator is a moisture-sensitive chemical that changes color when the indicated relative humidity is exceeded.

Chemicals

Some chemicals are:

Humidity indicator on the lithium-ion battery of an mobile phone
top: before wetting
bottom: after wetting
(battery model: Samsung AB653039)

gollark: Unfathomable.

gollark: It works fine after I unplugged it for a bit.

gollark: Duel bee.

gollark: I can try the battery reset pin if I find a paperclip.

gollark: Alternatively a low level software one.