If I ever get around to writing a book, and that book were to contain magic, I'd like to have a system worked out in advance for the different magical principles to be used. Over a series of posts, I'm going to try and outline the different magics I would like to use.
PotionsWhile typical usage would be for liquids meant for ingestion to induce magical effects, some games I've encountered include poltices and healing salves which are not typically ingested. Instead I'm using it as a more general term for objects created by the reshaping of existing magics. This is the mechanism for potions used in Harry Potter and the Methods of Rationality. To cure boils via potion is trivial but to do so with a spell is rather difficult.
The reason given for this is that the potion doesn't draw from the users well of magic, nor significantly on that of the potions' creator. Instead, existing magical objects like flubberworm mucus and doxy eggs are utilized in conjunction with more mundane, at least in the magical sense, items like porcupine quills or armadillo bile. When combined and manipulated correctly, the end result of a potion recipe is a 'charge' of magic that is released when the activation conditions are met, such as being ingested by a magical person for example.
While potion making is not magically taxing, it does require some magical source. Steps within the potions preparations, such as the intricate stirring patterns are actually minor spells that unbind the magical essence of the starting objects, reshape it into the desired form and alter the physical characteristics of the concoction into a suitable form (how else would you get a smooth liquid out of something with porqupine quills in it?)
Typically, potions contain at least one magical ingredient. While not necessary, it requires more skill from the maker as it must draw from their magics to supplement the brew. Hypothetically, you could contain the effects of a jelly legs jinx within a sweet but you can't just throw the jinx at the sugary treat and call it a day. Most other spells are channeled or instantaneous and therefore have no real concept of 'shelf life'. The process of converting spells to a form that can be stored is complex, but can be simplified by the right mundane components. The magic must also be keyed to an activation method else it will remain contained until it dissipates, degrades, or is reshaped appropriately.
The mundane components within potions procedures serve as foci for the spells being cast and can greatly simplify a procedure. The correct arrangement of mundane items can produce a resonance effect and greatly improve the end result. A potions master must balance their ingredients to optimize for time, cost, magic, and the level of precision required.
Anything that comes in close proximity of magical creature retains some residue for a time and therefore many things classified as mundane items hold small but detectable amounts of magical energies. For this reason, the term 'mundane components' refers to items that are not in themselves inherently magical like parts of non-magical plants and animals.
Potions have a shelf life; that is, a time before the potions magic has dissipated or degraded to the point where it no longer can serve its primary function. While this varies with the nature of the magic being contained, the general principle is that for all other things being equal, a more powerful potion will dissipate at a faster rate than a less powerful potion, similar to how a pot of boiling water will have its temperature decrease by 10C much faster than one starting at 25C in the same conditions. Degradation depends on the how stable the magic is in its current state. Healing potions have typically long degradation times and may be suitable for years while something like a love potion would need to be administered within a week or two else the potion may produce some unintended results.
Potions is one of the more powerful disciplines of magic that I plan on including within a magical system if I were to build one, but the trade off for that power is cost, time and a much higher importance of planning.
Image source: http://kyflpa.deviantart.com/favourites/72213623/Potions-n-magic