I think that the processes used to make salt (like open pan evaporation) did not produce drinkable water at the time. The techniques for getting pure water (single pot distillation and freezing where both known at the time I think) from salt water where much smaller scale operations.
I think if your designing a Rego craft magic effect the yield and purity of the fresh water would have a lot to do with the result of your finesse roll. This would make it a little less reliable and more labor intensive method then a Perdo effect, but you would get two commodities out of it rather then one.
Thanks to the way continuing Perdo effects work it would be easy to make a pipe or even canal that destroys the saltiness of any water that passes through it this could give you a very large yield with almost no labor.
If you wanted to get all techno magic you could actually build large pot stills enhanced with some CrIg and PeIg effects. Since I believe the two biggest limitations on early distillation was heat control and effective cooling.
A really odd solution that might or might not work depending on how you want Hermetic magic to work would involve Muto magic. If you could use a target part spell, perhaps with a terram req, to transform the salt present in the seawater into something that doesn't dissolve in water. In theory that would force the salt out of the solution and you could manually separate it from the water. (or use a rego req to put it in a nice neat pile off to the side) After the spell expires you have perfectly normal salt and perfectly normal water.
Totally irrelevant for Rego craft magic though , as you do not have to supply either heat or cooling.
If your Finesse roll is too low , unless you botch , you simply reapply the spell until you get potable water.
I have to second the Perdo idea. It's base is level 15 though, which can easily get up to higher levels to have an enchanted distiller. (+1 Touch, +14 levels for continuous effect, +x number of magnitudes for the appropriate size), so at least level 34.
At the risk of opening a can of worms, per the core rules on Perdo, using it to remove the salt from sea water will not work to create potable water. If anything, you should be using Creo on the salt water to make it sweet water. You're making it a better form of water, which requires Creo and likely a Ritual, not Perdo. Under the same logic, you could Perdo away the poison in someone's body to heal them. It doesn't work that way, you have to use Creo.
Because of the above, you should just use Rego. Distillation was a well known process by both the Ancients and any alchemist worth his salt.
The essential nature of seawater is to contain salt.
You can't Perdo it away permanently , same as you can't permanently destroy the weight of something.
Seawater is its own thing , it is not just freshwater that contains salt "in solution".
I disagree. From a medieval perspective, water is water. The oceans are filled through rivers, streams, and rains with sweet water and then it becomes salty.
You can make it whatever answer you want in your own saga though.
Which means that you use Creo to improve seawater to freshwater and using Perdo to remove the salt makes it a worse form of water ,
thus not freshwater and hence less drinkable or usable than before.
As I've said before sea water is not bad water. I don't believe you could use perdo to turn sweat water into salt water because that would mean creating salt. But you can destroy the salt you know is in sea water to make it sweet. Sure you can drink it but that doesn't mean it's inherently better. A bucket of fresh water would kill most any saltwater creature put into it does that make it worse then salt water.
Yes perdo can't be used to improve things directly you can't sharpen a sword with perdo because a sharp sword is better then a dull one. But you also can't use perdo to make adder poison more poisonous. You could however perdo said poison to make it weaker.
By the same token a fine wine with poison added to it is still good wine. All the Creo magic in the world isn't going to destroy any of the poison in the wine. Target Part PeAq should however do the trick.
I've been thinking about this for my island covenant. A couple methods I've found:
CrIg base 4 would let you do it the mundane way, just without needing fuel. No Finesse required since you're just making the salt pan hot enough to do the boiling/distilling.
ReTe(Aq) either 2 or 3. Make a box with two compartments. Fill one with salt water, then this spell to move the salt in the water to the other compartment. Might require finesse as a Rego Craft, but only around 3. From my reading desalination was easy to do as long as you didn't fall asleep, and you're only speeding it up from a day or so to momentary.
MuAq(AuTe) base 4 might work. Aq and Au to change water into vapor, Te to keep the salt from changing into vapor. Or maybe no Te req, but target Part instead.
By the way, desalination is explicitly listed as PeAq in the main book. Page 123. Also covers de-alcoholing, which implies that it would also cover de-poisoning. Interesting that you both MuAq and CrAq can make something poisonous.
In general, anything a mundane person could add or remove from water, I'd let a magus remove using Rego.
Well, the idea was to use this to create a fresh water LAKE in a previously (mostly) barren island after you secure the rights to settle it from mundane authorities for a pittance. So a box might be slightly smaller than what I was thinking about. :mrgreen:
Curious that PeAq thing to remove salt. Will have to check it. Nice catch
Ah, you want my OTHER invention then :mrgreen: . PeTe a ditch from the shore (just above the low tide mark) to where your lake will be. Install this enchanted trough (ReAq or PeAq, range touch, target part, momentary, continuous effect) in the ditch. Salt water will come through the ditch at high tide, have salt removed as it passes through the trough, then keep flowing into the lake. Trade the salt away for income.
If you have a pre-existing salty lake, do the same thing, but use rego to make the water flow into the trough then back out into the lake. Maybe this nice enchanted pump to pump water into the top end ?
Double check the ReAq guidlines you can boil (or freeze) water with rego alone without any Ignem or Muto necessary. In theory doing that would leave behind most of the salt in both cases just like when water naturally changes state.
Of course you should be able to Perdo away poison from a body. But it wont heal any damage caused by it up until then.
Otherwise you´re disallowing indirect and secondary effects, and that gets silly results.
Like, how Perdo can no longer be used to slice up wood because you can get planks out of it.
Or Perdo being unable to destroy bad weather because it makes the weather better...(told you it got silly)
Using Perdo on a knife to improve the edge by removing metal also becomes impossible despite being all nice and proper. And so on.
You also wont be able to kill someone with ANY sort Creo magic. Because even if its CrIg, its damage makes a person "worse" indirectly, just like a PeAn/PeTe/PeHe "destroy poison" spell indirectly makes a person "better".
Essentially, you break the established paradigm of magic one way or another.
So a box might be slightly smaller than what I was thinking about. :mrgreen:
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