Empty Potion

An empty Potion can be used to contain almost any liquid by immersing it up to the neck while held. A Potion can hold multiple liquids at the same time. Though Potions can spawn containing various powders, it is not currently possible to put any powders back into them. Filling an empty potion from full takes a little under 5 seconds when completely immersed in liquid.

Aquiring
As expected, an empty potion can be acquired by emptying a Potion
 * Use the left mouse button to spray out the contents until it is empty. (Takes ~16-17 seconds from 100%)
 * Right click the potion from the inventory screen to drink 10% of its contents (note that hazardous contents will cause damage to you, see this page for a list of all status effects).
 * Puncture a (dropped) filled potion, causing its contents to leak out (the potion will function normally or "repair" itself when picked up, since the game doesn't track damage on a potion that isn't broken outright). This risks breaking the potion (turning it into a useless 'glass', but can be done with reasonable safety using low-damage spells such as Spark Bolt and Bouncing Burst.
 * Rarely found as a natural spawn on potion-type pedestals.