[alt-photo] Re: Can I convert a light table to UV light source?
jseigel at panix.com
Fri Aug 13 17:26:41 GMT 2010
On Thu, 12 Aug 2010, Phil wrote:
> Can I convert a light table to UV light source by just replace 24" or 48"
> regular light tube with BL or BLB light tube the same size and use as a UV
> light table/box?
> Usually a light table has 2-4 tubes. Will the UV light power might be enough?
> Let's say the light box has 4x48" tubes, how long time it takes to expose a
> cyanotype prints? My regular mid-day cyanotype takes 12-24 minutes.
In my experience, a light table configured for viewing transparencies
works well with the plain light bulbs a few inches apart.... but for
exposure (such as cyanotype) they should be close enough so you don't get
hot spots. And the closer the paper, obviously, the closer the bulbs have
I don't work extremely large (IMO more trouble than it's worth), but my
cyano exposures range 10-15 minutes... this of course is affected by how
far the bulbs are from the image, how close they are together, the density
of the negative, the density of the cover glass (I also found exposure
varied depending on the glass itself & its thickness. And a shocker in my
first class -- discovered, finally, that a previous teacher used glass
guaranteed UV proof, which was of course why nothing came out !), how long
the emulsion has been on the paper (after 1 day it gets slower), also (I
assume) the chemicals themselves -- how fresh they are, and all the other
variables of paper, humidity, coating, negative density, etc. (Some papers
are --- I forget what they call it -- something like "pH neutralized")...
and I wouldn't recommend them for cyano, or anything else, for that
But if you're working with familiar, relatively fresh emulsion, and known
paper....just don't look directly at those bulbs for longer than
necessary. Plus, maybe 48" bulbs are possible to avoid? ( Harder to handle
& waste of electricity.)
(Someone on the list -- or maybe everyone on the list but me -- will
remember what the BLB -- or blacklight blue -- bulbs are for, but my
recollection is, again, they give less light & cost more, also are
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