Humidify

The Humidify spell will fill all empty water-carrying vessels in a player's inventory with a single casting, including buckets, fishbowls, jugs, vials, watering cans, waterskins, bowls and clay. A player receives 65 experience regardless of the number of vessels they have filled. Fishbowls and watering cans are not tradeable if they contain water.

Players travelling in the desert may find this spell useful so they can refill their waterskins without cutting cacti. Farmers on Lunar spells also find Humidify useful when farming multiple allotments, and may use Cure Plant and Fertile Soil hand in hand.

Casting humidify can also be a good way of training magic while making a fair profit. This can be done by buying empty vials from an NPC store such as the Shilo Village General Store or the Lunar Isle General Store and converting them into vial of water. You can also use humidify to help save time when making soft clay by having the dry clay in your inventory, and casting the spell. This turns all clay into soft clay. Players need a steam battlestaff for maximum efficiency.

To maximise training with this spell it's best to use a fishbowl and set it underneath the spell spot (as if you were high alchemising) and to use the "f1" and "f4" keys to switch back and forth between spell and inventory. This makes it extremely easy to cast the spell repeatedly, since the fishbowl has a 1-click empty. It is at the same speed as casting high alchemy since both spells give 65 experience. Note that casting high alchemy is usually a lot cheaper with potential profits when alching the right items. Casting humidify on a fishbowl and emptying it again will lead to a guaranteed 100% loss. When you first hear the sound effect, it means that all vessels have been filled. If timed correctly you can bank or train with the fishbowl with ease.

A note about the above method: Windows users can save time clicking by using a function known as MouseKeys. Experience users follow this direction to find the menu: Control Panel -> Accessibility Options -> Mouse -> MouseKeys (turn it on). Vista users might have a harder time, but the process is best explained on the Microsoft website. What this does is that it allows a person to use the 5 key on their number pad as a left-click button. You can also set the mouse aside so the cursor doesn't slide around.

Profits
This table assumes all items are bought on the Grand Exchange and sold afterwards for guide price. All staves may use equivalents (eg. Mindspike (water) instead of Staff of water)

Trivia

 * Using Humidify used to be a common spell used irrelevantly in the Soul Wars minigame, when it was first released, until Jagex changed it so that players trying to cast the spell receive the message: "You're here to crush souls, not to play with pretty clouds!"
 * Humidify will not fill a Bailing bucket.
 * After an update on 5 July 2011, humidify can no longer be cast in Castle Wars. Players attempting to cast the spell would receive the message "Please go somewhere else if you want to do that."
 * Humidify used to make a loud popping sound, but it was removed because players complained it was annoying.

Humidify