Wikia

This official news post is copied verbatim from the RuneScape website. It is copyrighted by Jagex.
This update was added on 7 February 2012.

Optimise your inventory by buying or creating the new potion flasks. These items act as larger vials for your potions, allowing you to store six doses rather than the conventional four – perfect when conquering bosses.

Should you wish to create the vials yourself, you’ll need a brand new resource called red sandstone. With a Mining level of 81, you can mine the non-tradable red sandstone north of Oo’glog (south of the Feldip Hills). You can mine a maximum of 50 red sandstone per day.

Take the sandstone to Oo’glog (after completing the As a First Resort quest), to Rutmir’s robust glassmaking machine. You can use the machine to fire the red sandstone into robust glass, which can be blown into potion flasks using a glassblowing pipe, as long as you have a Crafting level of 89. Decant potions into the flasks and feel thoroughly prepared for long combat trips (flasks will shatter once emptied of their contents).

Completed flasks are tradable. We expect entrepreneurs with the Crafting and Mining levels to make a healthy profit, should they choose to sell them on.

Paul
RuneScape Content Developer

Summary:

Where to start Potion Flasks:

Speak to Rutmir in Oo’glog.

Requirements to start Potion Flasks:

Level 81 Mining (to mine red sandstone)
Level 89 Crafting (to craft flasks from sandstone)
You must have completed As a First Resort

In other news...

- The Seal of Passage is no longer required when visiting Lunar Isle after Lunar Diplomacy. As such, the Elite Fremmenik task set has some new rewards:

Up to 28 Suqah teeth or Suqah hides can now be traded in daily with Rimae Siralis for 9 noted pure essence each.
The NPC Contact spell now allows players to switch from the Lunar spellbook to the ordinary spellbook.
The Seal of Passage now has a daily teleport option to Lunar Isle.

- The graphics for the Barrows equipment have been tweaked based upon player feedback.

- It is now possible to decant potions into any dose variant, and also possible to split potions into smaller doses by using a 2-dose potion on an empty vial.

- Slayer-specific drops in Dungeoneering can now only be picked up by the player who dealt the most damage to the creature for the first 30 seconds.

- Several monsters have had their Combat level adjusted to reflect that the monsters have differing combat behaviours. No monster stats have been adjusted with this.