Hygroscopic

a.	1.	Of or pertaining to, or indicated by, the hygroscope; not readily manifest to the senses, but capable of detection by the hygroscope; as, glass is often covered with a film of hygroscopic moisture.
	2.	Having the property of readily inbibing moisture from the atmosphere, or of the becoming coated with a thin film of moisture, as glass, etc.

Adj.

1.

hygroscopic - absorbing moisture (as from the air)

absorbent, absorptive