So, I have a bathtub and I want to use my CrAq to fill it with water. Simple enough. However, can I also create the temperature of the water within the dictates of CrAq? I will assume a 'room temperature' tepid bath should be no problem, but how far can my created water go in either direction? Can I make a cool bath, a freezing-cold-but-not-yet-ice-bath? How about a warm bath, or a tub full of boiling water. The guidelines don't seem to mention temperature. Do I need to pop in an Ignem req to get any variation of temperature, or maybe just for the endpoints? Or does this fall into creating "unnatural" water? Inquiring minds would like to know.
Creating a warm or cold body of water seems a straightforward Creo Aquam effect subject to personal finesse. The water will then equalize with the surrounding temperature.
A boiling or freezing cold body of water encroaches on Ignem requisite.
Maintaining a hot bath for a duration is fairly clearly an Ignem requisite.
Note that any dirt removed can be expected to remain once the created water vanishes, and will dirty the bath the next time it is filled, unless cleaned out.
for me, as I understand the relation between Ignem and Aquam :
with Creo, you can create ice water (cfr dagger of ice for instance) and I extend to the opposite, so you can also create boiling water.
with intelligo, you can say the temperature of a liquid (one mundain property).
but if you want that this temperature stays on a non-natural way (like a bath who stay boiling during 1 moon time), you need a Ignem requisite.
If you want change the temperature of your bath you have two ways to do it.
Using Rego Ignem spell with Aquam requisite, to adapt the temperature or using Creo Aquam to add some cold or hot water.
I will have tendency to ask a finesse dice to have the precise temperature, like a 12 ease factor for the exact temperature and a 6 for approximation. Using Rego Ignem would be easier than adding Creo Aquam.
Rego aquam in the core rulebook at lvl 3 states "Change a liquid in to the corresponding solid or gas". Mythic Europeans clearly know how steam and ice work, so logically a Creo Aquam with a Rego requisite could make the temperature what you want.
For someone who is not good at Rego, an Ignem requisite could make it warmer, a Perdo Ignem requisite for colder.
I referred to the Core rule book again and that all looks like an overthink. In the Creo Aquam guidelines "slightly unnatural liquids are one magnitude harder". One could class non-room temperature liquids as slightly unnatural. No requisite required, just 1 magnitude more.
The thing is that yes by RAW you can create water ice or steam, but it also indicates these will be water or steam at room temperature- highly unusual to be sure, rather than steaming hot or freezing cold without an ignem requisit (or the appropriate environment to create them in)
Other way around - to create normal (cold) ice you need no requisites, but if you wanted to create room-temperature ice (a state which water cannot be in naturally) you would need an Ignem requisite.
"Thus, to create ice you need only Creo Aquam. [...] A Creo Aquam spell with an Ignem
requisite could create warm ice — still solid, but warm." Core rule book p79
Rego Aquam is stated to be able to change water into ice or steam without needing any requisites since those are states that water can be in naturally.
I am pretty certain the Rego merely causes the phase change only, with temperature changing just enough to match the current phase state (solid, liquid, gas) of the water - ie the natural temperature of water in that state. Hence ReAq can't control the temperature of the water within the same phase state. (sorry for the Physics terms)
I presume a CrAq spell has the temperature of the water produced built in. Otherwise it defaults to room temperature?
But don't forget spell sigils might affect the resultant temperature.
Great and helpful replies, thank you. This was more of a thought experiment rather than trying to actually fill a bath. Just wondering how you all thought this might work.
The next step puts the above into more of a gaming framework. Lets say I want to create a spell Mighty Torrent of Really Hot Scalding Water. Basically Mighty Torrent out of the book but the water is hot hot hot. Do I even need a new spell? If so, is it higher level? Need some reqs? The gamemaster in me wants to say yes but Ars Magica has its own definition of balance that occasionally eludes me (wow those magi can be powerful). Changing a little thing here or there leads down some pretty amazing rabbit holes!
The consensus in the aforementioned thread was that while water should be able to be created as steam it should not be able to scald without an ignem requisite, despite the fact that in terms of modern understanding steam, or even hot water, will scald at far lower temperatures than fire must reach to burn someone. Of course the laws of thermodynamics which explains why this happens are also not part of the ars magica world... as such I would expect that if you want warm water or even a mighty torrent of soothing steam that should be fine but in order to scald you would need an ignem requisit.
Thanks, that's the direction I was thinking after reading the responces. Ignem req makes sense if I am adding more damage as a piggyback on an existing damage spell.
I think my players will have no trouble with this.
I think that's exactly the right approach: look at the game outcome rather than at some physical model.
Is the heat mostly cosmetic, in the sense it does not produce a change reflected in the game mechanics? Then sure, allow it without requisites, possibly requiring a finesse roll to see if it's done just right or sort-of-right.
Does the heat produce a mechanical effect, like adding damage? Then look at the damage and set the level, requisite etc, accordingly to make everything balanced with other damaging effects.