Prayer flask

A Prayer flask is a potion flask originally containing six doses of Prayer potion. It is created by using prayer potion on a potion flask. Each dose restores Prayer points, following this formula: $$70 + \lfloor 2.5 \times prayer level \rfloor$$ The flask is made by blowing robust glass, requiring 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.

After all six doses have been consumed, the flask will shatter and disappear.

To decant the potion into the flask, one must have at least 6 doses of prayer 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. The optimal inventory setup for decanting potions is 17 4-dose potions and 11 flasks.

Only the original, six-dose potion is tradeable on the Grand Exchange. Once the potion has been partially drunk, no more doses can be added to it, However, if you wish to decant the prayer flask into prayer potions, you need at most four doses of potion left in the flask and an empty vial, decanting a flask into a vial will still make the flask shatter.

If the full, 6-dosed version of this potion is consumed, each dose would cost about coins.