Quote Originally Posted by sanking
Just for the record, somebody posted a message ( not sure if on another thread on apug.org. or elsewhere) that the spiral BLB tubes can not be used in horizontal orientation due to the nature of the ballast. I have no idea if this is true, but I know for a fact that it was said, and the poster did seem pretty confident of the information.
Can't say for certain that BLB spirals are the same hardware, just with different phosophor/filter coating, but I have compact fluorescent bulbs in my kitchen fixture (got tired of changing the tungsten bulbs every 3-4 weeks). That fixture mounts the lamps horizontally, and though they do work well enough in that orientation, they're very dim when they first start; I have no way to be sure if that's due to orientation or temperature, however.

Given that VDB is working with a single spiral BLB in a reflector, I'll have to get another reflector (beyond the one that holds my 1950s vintage safelight bulb) and order in a BLB CFL. Then I can start working on cyanotypes and such without being dependent on sunshine (or working in the day, for that matter).