You could use Until, but "until the fire dies out" would be a poor choice, since it would be a ritual;
An alternative could be using Bargain, duration sun/moon, and setting a condition like keeping the candle lit up, but that also seems like a poor choice, magnitude-wise.
Inner mysteries offer a few alternatives, but most are unsatisfactory. Perhaps the one duration that might be handy here is the While (condition). The condition requires an activity from the target, so you might end up with something like "While holding a lit candle" which might not be handy if the target is expected to dance, etc. "While attending a social event" could be an alternative that would make sense, magnitude-wise.
Possibly the beauty comes from the dancing light of the fire? So the spell could move the flickering effect from the fire to light up the eyes of the person affected. The warmth could also be transfered to give them a "glow", and possibly affect their humours making them act appropriately for someone who is more ardent.
It would probably work, Bob, however it'd be a fairly high level effect that's not necessarily efficient. That sounds like Rego Imaginem base 10(to enable the visuals to follow the actual target arround the room where the candle is), +1 muto requisite, +1 changing images, +1 sight and sound, +1 touch, +3 fire... so that's a Re(Mu)Im 45 to make the person glamorous, with the side effect that the candle is now invisible and could be knocked over by someone unaware which could start a larger fire...
I found a math error on my spell list, I had Disguise of a New Visage marked as MuCo 10 and it is MuCo 15. I changed it for Supple Iron and Rigid Rope, MuHe[Te].
Then I learned Disguise of a New Visage from a lab text during advancement.
If you want to keep it formulaic and relatively low-level, I'd go with a metaphor instead of being litteral.
The simplest way is to just change it slightly, casting it for Sun duration, at night, like "Your beauty will outshine the stars above, for a whole, magical, night."
Then, you could just use Moon duration. Few candles will last that long, I guess.
Last, I believe you could use a non-standard RDT, the question being what's the closest duration chosen. If the troupe agrees with Fire, you're probably good, at the cost of 1 more magnitude. If they settle on Until, you're toast.
Thank you for the suggestions - I also took time to look over the Faerie Durations in ROP:F, but the only ones with a semi-variable length are the ones that draw on ritual magic. I could try to make an argument similar to how Muto Corpus transformations can be cancelled by symbolically removing an item, but that seems to be something only MuCo can do. (Thanks, Mutantes)
Actually, if I made the candles as a charged magical item, it fixes the entire problem, doesn't it? The candle will maintain concentration (Though technically the candle loses concentration at sunrise and sunset, so it'll have to be done after sunset...)
If you make the candles into a charged magical item, it does fix your entire problem, yes.
And if you want a candle that burns for a longer period, just call it a multiple charge candle, and have the activation being having a lit up candle. If it's still lit when the sun rises / goes down, another charge is expended.
Mm. That's a good thought and would work for things that don't require the same level of targeting.
But if the candle re-casts at sundown, the item has no target if the target is away at a gala. Still, I like the way this is looking.
Arguably, yes, you would need to increase the range to voice, sight or Arc depending on how far you want the target to be if it recasts, and plausibly an environmental trigger conditional to the candle being lit to avoid a flickering effect. On the other hand, since it's magical, I don't see any problem with a candle lesser enchanted device that doesn't really burn down while it's lit.
I'm glad you like it - I have plans. But really, Josephine's flaw is Curse of Venus, not Plagued by Faerie, so I don't expect a low-might faerie to really plague the Merinita for tribunal after tribunal. I have plans.