The extreme cooking flask is a potion flask originally containing six doses of extreme cooking potion. It is created by using extreme cooking potions on a potion flask. Each dose temporarily raises the player's Cooking level by up to 17 levels.
The empty flask is made by blowing robust glass, requiring level 89 Crafting and giving 100 experience. Red sandstone can be mined at Oo'glog and smelted using the robust glass machine also located at Oo'glog. Additionally if the elite Desert achievements have been completed, red standstone can also be mined from the Sophanem red sandstone, just east of Sophanem, north of Camel Warriors island.
To decant the potion into the flask, one must have at least 6 doses of extreme cooking potion in their inventory, as well as one or more potion flasks. Using the flask on the potion will open a menu to decant them. Flasks can also be decanted in bulk by Teplin Macagan in Oo'glog, who will decant vials into flasks, flasks back into vials, and flasks into flasks (combining doses); flasks are not returned from the latter two options.
Once a flask is filled with a potion, it cannot be refilled from a vial. After all six doses have been consumed, the flask will shatter and disappear. Flasks can be combined together, but the empty flasks will still be destroyed afterwards.
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