Buy OSRS Ale yeast
Ale yeast is a pot filled with yeast used for brewing in Old School RuneScape. It is the final ingredient you add to a fermenting vat. Once the yeast goes in, the brew starts to ferment. This makes ale yeast a key item for training the Cooking skill through brewing.
You need one ale yeast for every batch of ale or cider. It works for all brews, including Dwarven stout, Asgarnian ale, Greenman's ale, Chef's delight, Slayer's respite, and Wizard's mind bomb. These drinks give handy skill boosts. Some, like Dwarven stout and Slayer's respite, boost skills that few other items can.
Ale yeast is also a quest item in the Forgettable Tale quest. It is tradeable and noteable, but it does not stack and cannot be equipped. It weighs 2.834 kg.
Buying ale yeast saves you a trip to a brewery worker like Blandebir in Keldagrim or Metarialus in Port Phasmatys. You also skip the need to carry an empty pot. With ale yeast ready to go, you can start your next brew right away and keep your Cooking training moving.