It yields 65 experience per cast regardless of the number of vessels filled. It can also be used to extinguish the wall of flames in the Chambers of Xeric when fighting Great Olm or to refill waterskins in the Kharidian Desert instead of needing to cut cacti.

Does humidify work on flame wall?

It does work, you have to right click and select 'target'.

How do I use humidify Osrs?

One can cast Humidify on an inventory of clay to turn them into soft clay. Use astral runes, and equip a steam battlestaff to maximise profit and efficiency. Withdraw 27 clay and 815 astral runes, cast the Humidify spell, which will cause the whole inventory to turn into soft clay, open the bank, and repeat.