A friend and I just started making Pt/Pd prints. We both made fluroscent
tube light sources. I sort of based mine on the plans in the Palladio
catalog. In that catalog, they say that the 18" 25W bulbs give the shortest
times. I was attempting to get those bulbs, but when the order came in I
actually got some 32W 18" BL bulbs (I don't know the exact number but I
could check if you want). I haven't done a lot of printing yet, but so
far my longest exposure was 12 minutes and 3 or 4 minutes is more typical.
I used 7 bulbs, I was planning to use 8 when I thought I was getting the
25W bulbs, but the 32W's are bigger in diameter and I think 6 would have
been enough (for the 8x10 prints I'm doing anyway). My friend found some
40W 18" BL bulbs at Sears for their bug zapper. He just got 3 twin tube
shop lights and 6 bulbs for a lot less than I spent. He had to take the
shop lights apart and re-mount the sockets for the shorter tubes (his
light cost quite a bit less than mine). His times were about 2 minutes
which is probably a bit too short (you can adjust it by adjusting the
distance between the bulbs and the negative of course). My tubes are
about 4 or 5 inches from the negative so I could get them closer and
still have even lighting. There is about 1/2" spacing between them if
I remember correctly.
By the way, someone was wondering about ballasts for some 40W bulbs.
These are actually the most common ballasts available. All standard 4
foot tubes are 40W, so you can use any of those ballasts. From what I
was told at the lamp distributor, the only thing that matters for the
ballast is the wattage of the bulbs the lenght of the tube doesn't
matter.
John Sparks