Used fillings of a column chromatography (mostly silica gel) should be completely dry. Curiously after use the colums are often simply mounted upside down and then left standing alone to allow the content to fall out. But the wet material is sticky and it may need days and even weeks to get it out! But if air is suckd through the column the job is done within one hour! (Have a solvent trap in the line between column and pump!) During the process a cold zone is moving through the column. If it had reached the end of the column and had then disappeard the content is free flowing again.
Silica gel and alumina are disposed as "operating materials".