RE: cyanotype exposure

My hunch has been that the film base is a strong uv filter. Any film
suggestions to avoid this problem?

-----Original Message-----
From: Richard Knoppow [mailto:dickburk@ix.netcom.com]
Sent: Sunday, November 13, 2005 9:25 PM
To: alt-photo-process-l@sask.usask.ca
Subject: Re: cyanotype exposure

----- Original Message -----
From: "Michael Koch-Schulte" <mkochsch@shaw.ca>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Sunday, November 13, 2005 6:10 PM
Subject: Re: cyanotype exposure

> Ron Klein wrote:
>> I am having some difficulty with my cyanotypes and I am
>> hoping for
>> some help.I get a very rich, deep blue on areas coated
>> beyond the
>> negative, but even the unexposed areas of the negative
>> are very
>> weekly colored. I have used exposures up to 45 minutes in
>> my homemade
>> exposure unit with a bank of 8 bulbs about 3 inches above
>> the contact
>> printer.
>> I use T max 100 predominantly. Any suggestions?
>
> Sounds like the TMAX is absorbing alot of UV? Try going
> an hour and a half?
> This sounds waaaayyy too long though. I usually print
> cyano in about nine
> minutes under BL UV fluorescent blubs. It could also be
> the glass in your
> contact printer? What's the stepwedge saying?
>
  If you have a BLB or similar UV lamp which blocks visible
light you can test for this by seeing how much flourescence
you get on a sheet of writing paper held against the
negative. I did this test using 4x5 sheet film and found
that T-Max did seem to block much of the UV.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com