Eye of Newt, Tongue of Bat

[Kwaj]

I recently had an idea for an urban fantasy story, centering around an alchemist who survives in a world of monsters and magic through the creation of clever and powerful potions and elixirs. Unlike a lot of urban fantasy, where the protagonist gets by on quick thinking and improvisation, our alchemist outwits and outmaneuvers her foes through careful preparation and planning.

The reason I'm posting about it here is that I want to sound out different potion-making processes. I quite like the one used in the Dresden Files, where each potion has eight components (five to accommodate the senses, one base liquid component, one to affect the heart, and one for the mind). However, I don't want to parrot Butcher's ideas; I want to come up with interesting and fun potion-brewing systems and ideas. Feel free to contribute yours below.

[Bohandas]

Every potion contains a plant, a toxic chemical, and part from an endangered animal. The deadlier the poison, the rarer the animal, and the greater the portion of the ingredients that are wasted the more potent the potion is.

This seems to be the idea behind "real-life" alternative "medicine"

[RedFred]

A potion may be ingested (i.e. healing potions) or designed to interact with the environment (i.e. molotovs).

Those that are ingested are built around the four humors of Melancholic, Phlegmatic, Choleric and Sanguine. The balances between these four elements produce specific effects in the consumer. For instance pure Melancholic potions cool the emotions giving you advantage in mental skills . After a potion is taken it imbalances the drinker who must either wait or ingest the other humors in equal proportion to balance out/negate the effects. More complex effects are made by mixing multiple humors together. Poisons can be created using the same ingredients as a potion but brewing it at night instead of day.

Potions that interact with the environment are naturally inert until they come into contact with a reagent, which can be anything but must be included in the formula (for instance, a potion could be inert until coming into contact with a specific type of stone). These are made from the four elements in two separate parts, essence and solution, one to determine the effect and the other to determine the resulting "substance". I.e. mixing essence of earth with fire would create something that hardened metals, and using a solution of water would result in an oil, while a solution of air would create a gas.
Fire and air would create an explosive material, and using a solution of earth would result in a clay like substance.

[jqavins]

Traditional sorts of potion ingredients are used - rare animal parts and plant matter - but they are never active unless also combined with various purified chemical reagents. That's why the potions of myth were so rare and have become rarer; in the past, practitioners of the magical arts and alchemists were mostly different people, alchemists actually taking a more scientific approach than we modern usually give them credit for. As the science of chemistry advanced, it has become far more separated from the magical arts. But only those few who are willing and able to combine these two arts are able to make potions that actually work.

In ancient times, the potions that worked included those few chemical substances that could be obtained and identified with adequate purity, e.g. niter, vinegar, carbon. Today, research may reveal many more potion recipes that are effective by combining, say, the ovary of a white mouse (approximately 100 mg), the immature blossoms of Queen Anne's lace (1 g), and dimethylsulfate, 0.43 molar in acetone (10 ml).

Potions are not brewed in cauldrons anymore, but rather they are prepared with great care in clean labs using modern equipment.

(Don't ask me what that potion does; I just picked some random ingredients.)

[Vogie]

I recently had an idea for an urban fantasy story, centering around an alchemist who survives in a world of monsters and magic through the creation of clever and powerful potions and elixirs. Unlike a lot of urban fantasy, where the protagonist gets by on quick thinking and improvisation, our alchemist outwits and outmaneuvers her foes through careful preparation and planning.

It sounds like you're making him Batman/Rocket Raccoon - that is, crazy-prepared. That could be a tough sell, depending on the story. This can work on a certain level, such as the first season of Prison Break, but an excessive amount of preparation and planning makes the encounters start looking dumb. For example, the climax of Ocean's 12 basically made the entire crux of the movie effectively pointless. You don't want to fall into the "shark repellent" level of preparedness.