Re: intensity of bulbs

[Jim Larimer <jrlarimer@gmail.com>]

I wanted to be less dependent upon the sun for my UV light source so I thought that I would start with a very basic setup and go from there. I bought 4 single strip black lights (24" long) at Home Depot ($15 each) and mounted them on a piece of ply, plugged into a power strip. The whole unit is suspended the height of a brick, on end, above my contact frame. The light strips are spaced about 2" apart, enough space that if I have problems with stripping I can add three more lights in the available open spaces. After a couple of experimental tries I had a success last night. I printed using  CMYK separations with cyanotype being my first printing. I mixed the cyanotype 1 pt "A", 1pt "B" and 1 pt H20. I exposed for 5 min. Next came Cad Yellow for 3 min. Then Perm Rose for 3 min. Then instead of a K printing, I redid the C with Windsor Blue for 3 min. Here is the result that I am pleased with:

http://www.flickr.com/photos/jim_larimer/3302316486/

I will keep playing around to find optimum printing times and pigment strengths, and to find out if I need to add more lights to my array.

Jim

On Mon, Feb 23, 2009 at 6:22 PM, Gordon J. Holtslander <gordon.holtslander@usask.ca> wrote:

I use 4 foot 40 watt tubes on my UV unit. I used 4 foot tubes because
they were the cheapest UV tube I could find.

My UV unit is made from 5 plain double tube strip lamps - holds ten
tubes. The lamps are screwed to a piece of plywood so that the spacing
between the tubes is consistent - they are about an inch apart. The unit
is around 2 ft by 4 ft. The whole unit is on hinged to the wall so the
the tubes face the counter surface when its "hinged down" . When I print
the unit sits 4 inches above a couter top. - it has chain stays with
turn-buckles to hold and insure its level. When I'm not printing I hinge
the whole unit up and latch it to the wall. I can get away with having
such a huge unit. When I'm not printing it does not take up any counter
space - just some wall space. I use the same counter top for coating
paper and much of the other work in my darkroom.

I had considered using high intensity tubes and ballasts - but I didn't
think the slightly shorter printing times justified the expense. Might
be worth it if the cost of high intensity tubes and ballasts is much
cheaper now.

If I didn't use strip lamps I could have the tubes much closer together
-(the strip lamp design governs the lamp spacing) allowing a more
intense output, but my printing times haven't been as issue yet ...

Gord

geoff chaplin wrote:

>The length of the tubes is primarily determined by the maximum size of the
>print you wish to make - plus a margin to avoid light fall-off at the ends.
>I use 24" tubes to print 20" negs without a problem.
>
>At the same distance from the tubes the light intensity is proportional to
>the power of the tube (assuming the same type, efficiency etc). So a 40w
>tube would be twice as bright as the 20w tube.
>
>Geoff Chaplin
> $B%8%'%U!!%A%c%C%W%j%s(B
>
>geoff@geoffgallery.net
>www.geoffgallery.net
>Skype: geoffchaplin1611
>UK mobile ($B1Q9q$N7HBSEEOC(B): +44(0) 7770 787069
>Japan mobile ($BF|K\$N7HBSEEOC(B): +81(0) 90 6440 7037
>Japan land line / fax ($BF|K\$NEEOC$H%U%!%/%9(B): +81(0) 166 92 5855
>
>
>-----Original Message-----
>From: Barry Singer [mailto:bsinger@sasktel.net]
>Sent: 24 February 2009 07:18
>To: alt-photo-process-l@usask.ca
>Subject: intensity of bulbs
>
>A cursory search of the archives doesn't help me answer this question.
>Perhaps some one can help?
>
>Does a 24" bulb at 20 watts have the same intensity as a 48" bulb at 40
>watts?
>
>Barry
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