Re: UV light box

Darkrooms, Department of Art <darkroommanager@...>

Here at the university we have two exposure units. Both use the same bulb
T12 40BL GE bulbs, 48" length. In our "fast unit" the bulbs are 1 inch
apart and about 3" from the surface of the print. The "slow" unit has
bulbs that are 6" apart and about 8" from the surface of the print. I
find that both have even illumination throughout, but the slow unit has
exposure length about 10% longer.

I hope that this is helpful! Good luck and happy printing.

Jennifer M. Gioffre
Teaching Support Specialist

Architecture Art and Planning
Cornell University
120 Tjaden Hall
Ithaca, NY 14853

o: 607-255-4207
f: 607-255-3462

On 3/6/14 7:45 AM, "Jorj Bauer" <> wrote:

I think you'll be fine.

I built a 24" square exposure box from 10x GE 22" blacklight enclosures
(it was what was readily available, so I ran with it). The prints sit
about 6" above the bulbs (I flip over my vacuum frame, so it's
upside-down during exposures).

The bulbs are spaced evenly across the box, which means they're a little
over 2" apart. But I wired it so that there are two power switches, one
for bulbs 1,3,5,7,9 and one for 2,4,6,8,10 (so that I can turn off half
the bank if I want to - I didn't know if this would be overkill in terms
of UV source or not).

I ran some tests using half of the bulbs - so, spaced a little over 4"
apart - and saw no problems. I've always used all of the lights since,
though. My average exposure time is around 6 minutes for most kinds of

The lights are GE model 10186, 15w blacklight T8s.

Hope that helps,
-- Jorj

On Mar 5, 2014, at 10:42 PM, Bob Cornelis <> wrote:

Thanks, Marek!

I¹m getting the impression my hope of putting the bulbs 4² apart is
very misguided and that they need to actually be quite close to each


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On Mar 5, 2014, at 7:29 PM, Marek Matusz <>

Ok mine home build unit has the tubes 3" from the print this is the
distance from the edge of the tube. Distance between the tubes again
edge to edge of tubes is 0.5"

Sent from my iPhone

On Mar 5, 2014, at 6:41 PM, "Laura V" <> wrote:

Hi Bob,
I was asking here about lighting a couple of months ago and got this
link from Kees Brandenburg showing his lightbox (maybe he's too busy
moving the list to see this thread) :)

As you can see, the bulbs look pretty close together. I ended up
having a similar unit built (which took almost 3 months - I just
picked it up so haven't tried it yet!) I had the electrical part done
at a place specializing in fluorescent lighting and asked them to put
the bulbs as close together as was safe to do so. It's in the trunk of
my car down the street at the moment and it's snowing, so I'll get
back to you as to the exact distance. Mine has 10 bulbs and the width
is smaller than the 24" (60cm) length, so that is a lot closer than 4
inches apart.

Perhaps someone else can fill us in whether they need to be that
close together, or maybe it's just a matter of the more bulbs the
quicker the exposure.

Best Regards,

On 3/4/14 9:43 PM, Bob Cornelis wrote:
I am planning on building a UV light box and have a question about
the layout of the bulbs. Upon the recommendation of a friend who does
alt process work I plan on buying these tubes:

My questions are how far apart should I mount these and how many do
I need to provide good coverage to expose up to 20x24² (though I¹m
not sure I¹d ever go over 16x20). I plan on having them about 4²
above the surface of the prints.



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