For my DIY UV box I bought up Noma Back Light Blue compact fluorecents. I found mine at Canadian Tire. My initial effort used 2 bulbs for a 4x5 box. I proofed the concept, and scaled up to 9 lamps to allw me to print up to 11x14. I use it with Dr Mike Ware's Cyanotype formula, and find my exposure times are between 20 and 60 minutes depending on how dense the negative is.