Not possible, torches only slow the spawning down. Has to be with blocks (8x8, the 8 sides facing the lower coords).
hmm, is it different in SP? cause i didn't really get why thoose stopped spawning with torches. Anyways - thanks for the reply.
I can't tell if that's a troll... if it is, one torch will not disable it. Yep, I always have them spawning, even with 10-15 torches near.
Well I only ever put down one torch and no mobs ever spawn. Perhaps it is only slowing the spawn rate down, but it's slowing it down a lot, enough that I won't have to worry about one coming out because I'll be gone before it does. Blaze spawners might have different properties, but it doesn't matter to me because when I find one I don't want to disable it, I want to farm from it.
Blaze will spawn around a spawner if there is a light level of 11 or lower (lower half of their body). You can completely stop a blaze spawner from spawning blazes by placing a layer of blocks at the same y coordinates, followed by placing torches on this layer (y coordinate +1).
In addition to this, the bottom layer would be as the same y coordinates as the spawner. Just replace the torches with solid blocks.