Several things can happen if an object becomes wet. The most common effects are to rust metal and make blank scrolls and blank spellbooks. The normal way to make an object wet is to dip it into water, usually a pool or moat, or to submerge yourself while carrying the object. Rust traps can also wet worn or wielded rustable items, and wielded scrolls.
Note some special sources of water will not wet an object, but will have a different effect. #Dipping into a pool, moat, or uncursed potion of water will always wet an object, but never the contents of containers. Dipping into a fountain will always wet an object and can give special effects, including converting a long sword into Excalibur. Dipping into holy water or unholy water will never wet an object.
What happens when an object becomes wet?
- Contents of containers are affected only if you fall into water, not if #dipped.
- Nothing happens to an object protected by grease, except that the grease might wash off (50% chance).
- A potion of acid will explode. Harmless if you fell into water, but it will deal d10 damage if #dipped ("killed by elementary chemistry").
- Other potions will become diluted. Potions already diluted will become uncursed water. (You can make uncursed water by twice diluting potions, then later you can change the uncursed water into holy water.)
- Scrolls and spellbooks become blank; if you have a magic marker, you can then write new ones. The resulting blank objects will have the same BUC status as the original. The Book of the Dead cannot become blank. ("The Book of the Dead suddenly heats up; steam rises and it remains dry.") Neither can a scroll of mail. Thus if you send yourself much mail during the game, you cannot use it to supply yourself with blank scrolls.
- Iron objects might (50%) become one step more rusty. Rustproof objects and objects which are already "thoroughly rusty" will not rust. Other metals do not rust.
If you dipped into an uncursed potion of water, and one of the above effects occurs, you lose your potion; otherwise you keep it ("Object gets wet."). You keep your potion if the dipped object was greased. It's a waste to use your potions this way; it is better to dip uncursed potions of water into holy water to make more holy water. If you want to manufacture uncursed potions of water or blank paper, do not dip into potions of water; dip into a pool, moat, cancel the items, or (less preferrably) dip into a fountain. Dipping a container will not dilute any potions inside it.
The safest technique for dipping is to wear water walking boots or be flying (levitation is not enough), walk over open water that is devoid of sea monsters, and dip away. This is not always an option, so second to this is to drop any inventory item you don't want to get wet, get unencumbered, and walk into open water. You will escape the water unharmed and have any scrolls in your inventory blanked and potions diluted. Be careful! This also happens to items in a bag, unless it is oilskin or has been temporarily protected with grease. With high Luck, you might need to try several times. Swimming is safe because you can only drown if you are encumbered from your armor or loadstone, or if monsters block all adjacent land squares. Another slow, but somewhat safer method is to remove any rustprone worn items, wield the item you want wetted, and repeatedly #sit on a rust trap. This does not work for potions or spellbooks.
Fountains are the most readily available means of dipping objects; however, they can be quite dangerous for unprepared characters and will dry up rather soon. Water demons, water moccasins, water nymphs, and cursing the dipped item are all possible results of dipping in fountains. Unless you have decent AC (around 0 is a good baseline), poison resistance and/or magic cancellation, a decent weapon, and a way to remove curses, it is better to find another means.
It is recommended you create pools near your main stash for unlimited, no-side-effects water.