Big Cauldron of Battle

Actually, the number of flasks obtainable from one is specifically made so that players have an incentive to reach the 19th level of Guild Rewards, which is Happy Hour.

Happy Hour, once obtained, makes all flask cauldrons produce 50% more flasks. Therefore, this would produce 25 flasks to an appropriately leveled guildie, just enough for a 25 man raid. Not a bad deal for the 12 flasks invested in making it.

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Once your guild earns the achievement Mix Master (now 1000 cataclysm-only flasks) you can purchase the recipe Recipe: Cauldron of Battle from a guild vendor if you have friendly reputation or higher with your guild.

Once your guild earns the achievement Better Leveling Through Chemistry (now 3000 cataclysm-only flasks) you can purchase the recipe Recipe: Big Cauldron of Battle from a guild vendor if you have friendly reputation or higher with your guild.

There are 3 Guild Perks that affect Cauldrons:

Chug-a-lug (rank 1) (50% longer flask duration, guild level 10)

Happy Hour (50% additional flasks, 7-->10 or 20-->30, guild level 20)

Chug-a-lug (rank 2) (100% longer flask duration, guild level 22, does NOT stack with Chug-a-lug (rank 1))

Still unsure if the Alchemy passive Mixology will stack with the guild perk Chug-a-lug -- it is possible that Alchemists will receive 3 or 4 hour flask durations.

Making a cauldron is always more efficient than drinking a normal flask. For Recipe: Cauldron of Battle you receive 7 flasks for the price of less than 5, as 8x Deathblood Venom is not as expensive as a flask. The larger version, Recipe: Big Cauldron of Battle is even more efficient, as it requires no deathblood venom, and you simply receive 20(30) flasks for 12 flasks.

Assuming your guild is level 22, you do 25-man raids, and you have unlocked Recipe: Big Cauldron of Battle with the achievement Better Leveling Through Chemistry , you will need 48% as many flasks as usual for everyone to be flasked up (12 flasks required for 25 people), and the flasks will last twice as long as normal, for a net flask-effectiveness of 416.67%, or alternatively a net flask-material-reduction of 76%.

Multiple cauldrons may be dropped at the same time, so as soon as you unlock Recipe: Cauldron of Battle for maximum material efficiency you should drop one cauldron in a 10-man raid, or 3 cauldrons in a 25-man raid, and have the people that miss out flask or elixir themselves normally.

Happy cauldron brewing!
Hungraa

Now am gonna get meh pointy wizard hat, a black robe and a big stick for mixing meh evil cauldron stuff :3