Re: sun vs exposure unit

The trick with the sun is that the UV portion of exposure isn't
consistent.

A possible solution could be to use a printing out process - like
cyanotype and a step-tablet to measure the cumulitive UV exposure.

You have a small printing frame with a split back, or maybe just tape
the cyanotype and step-tablet. Every few minutes shield the frame from UV
- open the frame and see how many steps have exposed.

You would have to do some testing to see "how many steps" are needed to
expose your photopolymer plate. But once this is established you may be
able to get consistent exposures with the sun.

can get step-tablets from http://www.stouffer.net/TransPage.htm

Others have done the same thing on a much simpler scale - putting a dime
on a piece of cyanotype and gage the exposure by picking up the dime and
gaging the exposure by the difference between the unexposed cyanotype
under the dime and the exposed cyanotype.

Gord

On Thu, 26 May 2005, Barb wrote:

> Actually I live in Texas, so ok there. Also, am doing something a bit
> different. I'm exposing photopolymer for art rubber stamps. I have an old
> graphic arts light table that I use as an exposure unit (for both photo
> processing and the rubber stamps)--I just replace the regular flourescent
> bulbs with UV bulbs... but the bulbs were damaged during a move and I need
> to be working between now and the time the new bulbs arrive. I really
> appreciate your input!
>
> One question: what process are you using?
>
> Also, once process is posted, would someone please post their own times
> with an exposure unit for the same process? That would be so helpful!
> thanks again,
> b
>
> At 03:57 PM 5/26/2005, you wrote:
>
> >I have to rely on the sun. I'm in Phoenix, so you'd think we'd have a lot
> >of that, wouldn't
> >you? Unfortunately it is unpredictable due to high thin clouds and
> >haze/pollution. In
> >December and January, there's often a cloud cover, and it can't be
> >predicted, so coating
> >paper for a schedule involves a crap shoot. Also, between mid May and
> >about October
> >1st, my brick-enclosed patio gets into the 150+ F degree range. The risk
> >of melting
> >things like, oh, negatives and Pictorico seems to be very real. I can't
> >compare to UV
> >because I'm still building my UV box; but times are fine, in the range of
> >2-4 minutes
> >depending on negative material, negative density, and print medium. Real
> >film negs take
> >longer, printed negs can be much shorter. The main problem with sun, even
> >here in
> >Arizona, really is variance - not only the season and the intense summer
> >heat, but also
> >the longer exposure times needed before about 11AM and after about 2PM -
> >longer then
> >and difficult to gauge. It's a real PITA. That's why I'm working on a UV
> >box; but the sun
> >is perfectly doable if you set your mind to it and happen to live in
> >Arizona. :)
> >
> >Mike
> >
> >On 26 May 2005 at 14:50, Barb wrote:
> >
> >Date sent: Thu, 26 May 2005 14:50:20 -0500
> >From: Barb <rubyslpr@sbcglobal.net>
> >Subject: sun vs exposure unit
> >To: alt-photo-process-l@sask.usask.ca
> >Send reply to: alt-photo-process-l@sask.usask.ca
> >
> > > Does anyone use the sun rather than an exposure unit? I was just
> > > wondering if anyone can tell me how it compares (time) to UV exposure
> > > unit. If so, please include your location and the time of day you do
> > > your exposures? Thanks so much, Barb
> > >
> >
> >
> >
> >
> >
> >
> >--
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>

---------------------------------------------------------
Gordon J. Holtslander Dept. of Biology
holtsg@duke.usask.ca 112 Science Place
http://duke.usask.ca/~holtsg University of Saskatchewan
Tel (306) 966-4433 Saskatoon, Saskatchewan
Fax (306) 966-4461 Canada S7N 5E2
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Received on Thu May 26 16:16:54 2005