Re: best light for light box

[Judy Seigel <jseigel@panix.com>]

On Mon, 13 Aug 2001, fotomagia wrote:

> I wonder whether Philips brand is available in America, but I have their
> leaflets covering three types of UV tubes:
>
> 1) Actinic lamps, colour /05, emitting UV between 300 and 460 nm with a
> maximum at 365 nm, to be used for insect traps, diazo printing and chemical
> processing.
>
> 2) Super-actinic, colour /03, emitting UV between 400 and 440 nm with a max
> at 420 nm, for diazo copying, phototherapy (treatment of jaundice in
> new-born infants) and growing coral in aquaria.
>
> 3) Germicidal, with a peak at 253.7 nm, used for killing and inactivating
> bacteria, viruses and other primitive organisms - for treatment of air in
> hospitals, food processing, air conditioning, disinfection of drinking
> water, waste water, recycled water in swimming pools, surface treatment of
> bakery products, disinfection of packaging materials and variety of
> photo-chemical process (!).
>
> I haven't tried any so I wouldn't know which are the best, as the proper
> wavelength for bi-chromate processes remains a secret for me (by the way,
> who knows the exact wavelength?), but my guess is that all should do the
> job.


Cross type #3, the germicidal, off your list... that's the low UV range, &
very dangerous to humans, especially human eyes. Also unlikely to be much
use for our processes, which tend to greatest sensitivity in the 350 to
425 nm range.

Second, in my experience, there is more difference between lots from one
manufacturer than different manufacturers. Which is to say, I've found
blacklight bulbs from GE, Sylvania, & Phillips for all practical purposes
the same.

In the US, you can also buy so-called "growlights" in fluorescent tubes. I
don't know the nominal range, but they took about an hour to give about
1/3 the cyanotype tone the BL bulbs gave in 10 minutes.

Some folks find "regular" fluorescent bulbs good for carbon printing (I
think it was the "bright white" type), but not for other processes.
They're probably the cheapest, but since the BL are rated for 7000 to 9000
hours, and exposures are one to 10 minutes, that's probably irrelevant.

Judy

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