Sean, I've been exposing cyanotype, VDB, and salt prints using the 13 W version of those bulbs, a single lamp in a reflector, with excellent results. I get exposure times only about twice what I'd need in sunshine, with the lamp about 20-25 cm from the printing frame (though with a single lamp, you'd need more distance for a larger print, the higher wattage lamp will help keep your printing times down). BTW, I've heard there are also 27 W versions of these bulbs available, which ought to give still shorter times.