Whatever the "certain book" is, that number is open to question. For
instance the resident expert at Voltarc, which makes bulbs of all kinds,
including the AQA bulb sold for platinum (tho it's made for aquariums)
says their tests show it's 415 nm. Theoretically, gum dichromate peaks at
360 nm, but he told me (I haven't tested this) there's enough overlap so
that dichromate printed equally well with the AQA (tho I suspect the
"curve" would be different). Last I heard, BTW, Voltarc was doing a
prototype of a bulb at 350 nm, called, if memory serves, "Black Light."
But this obsessing about the exact # of nms, is voodoo. Beside the point,
ultraviolet herring. Your glass, your mix, your paper and probably your
DNA will all affect the "curve" and speed of the print. Any so-called
"black light bulb" (as long as it's not BLB) will have its charms.
We did, BTW, some interesting tests of different bulbs last fall for
dichromates. See the archive....
> example, I know someone who has been offered a unit (ex-lithographic /
> printing, I think) which takes bulbs with a wave length of 365 nm - I could
> not tell her whether this was in the acceptable range or not ...
Any bulb nominally between 365 and 450 will be fine..... (Note that below
350 the UV light is more harmful to humans.)
Judy