It mentions several times in the fluff text of the Magic section that Thaumaturgy is slow, with even the fastest spells taking a minute or so. But when you actually look at the rules, the slowest part of Thaum (preparation) can be skipped if you're doing a reasonably simple spell and you have a high lore; then there's some number of exchanges to build up power. Which looks on the face of it like a character doing a really simple spell-- like, oh, pretty much any maneuver to add a temporary aspect to a scene, at difficulty 3, when done by a carefully built Submerged wizard-- might well be able to get it off in one exchange of power-building.
There isn't any kind of reliable time-to-exchange converter: a single exchange in a social conflict is liable to be far more than a minute, while a single exchange in a gunfight is likely to be far less.
So, given that, what does it really mean for Thaum to be slow compared to Evocation? I have a player who *really* wants to play a useful-in-conflict-time Thaumaturgist, but I also want his character to have a reason to fall back to his less-favored Evocation skills in some circumstances.
Things I've considered:
1) Yes, very simple Thaum spells really are as fast as arbitrarily complicated evocations; however, Thaum also always has the symbolic link restriction, so you're going to need to do some prep-work if you want to be applying even temporary aspects directly to an enemy. Use Evocation not necessarily for speed, but for lashing out at/defending against something you don't have any links to.
2) Thaum always takes some minimal number of rounds; even if you're skipping the serious prep phase, gathering your mind to prepare to cast the spell always
takes one round. (This seems clumsy, especially since it's nothing but a speed bump; there's not even a Lore role involved.)
3) Thaum spells can be cast in one exchange, but their effects are not instantaneous. The player only needs to spend one exchange creating and powering the spell, but whether the effect settles in on the next round or in a few rounds will depend on the GM's estimation of the speed of the conflict. (This seems like it would cause GM headaches, as well as reducing the coolness factor.)
4) As 1, but performing a Thaum ritual with no prep in a high-stress situation-- which will be most conflicts, but not necessarily all-- adds to the complexity. This departs a little bit from the book (after all, you're already making Discipline rolls to control the power) but encourages the player to go ahead and spend a round or two on maneuvers to create a more optimal spellcasting environment, thereby effectively slowing Thaum down without actually changing the power-building or spell-prep mechanic.
Anyone else have any insights, or suggestions as to which of these might work best in play?