RE: what I've learned about cyanotype thru PDN

Chris said "So I think you may be talking about humidity being a speed
benefit (for sure in pt/pd, maybe in cyanotype) vs. uneven moisture, which
is not."

Oh master (although not of pt/pd printing), Not always. One needs to make a
distinction between PT and PD when talking speed and relationship to
humidity. PT is slower at high humidity than at low humidity. PD is slower
at low humidity and faster at higher humidity. Both have relatively flat
speed changes in the 50% range. This is one reason that printing PT/PD
printing at 50 to 60% will produce prints that don't change speed due to
humidity. Another aspect of PT/PD is change in color based upon RH.

If you make your prints with only trace amounts of PT then you may indeed
have a hard time seeing either speed or color changes due to humidity.

Eric Neilsen Photography
4101 Commerce Street
Suite 9
Dallas, TX 75226
http://e.neilsen.home.att.net
http://ericneilsenphotography.com
 
> -----Original Message-----
> From: Christina Z. Anderson [mailto:zphoto@bellsouth.net]
> Sent: Sunday, June 05, 2005 9:04 AM
> To: alt-photo-process-l@sask.usask.ca
> Subject: Re: what I've learned about cyanotype thru PDN
>
> Loris,
> You are absolutely right that lavender color comes from alkalinity,
> (especially if you are using Ware's on the wrong paper you'll get horrible
> lavender highlights and the rest will be a dull grey blue). This lavender
> was directly the result of moisture left in the paper, because it had a
> wonderful bloom mark around it, like you get when you watercolor. I could
> replicate it I would think if I wanted to drip drops of water on the paper
> 5
> minutes before exposure. Try it and you'll see what I mean (and probably
> damage your neg).
>
> I have seen, therefore, lavender associated with both causes. To
> duplicate
> the alkaline cause, all you have to do is coat the cyanotype with Future
> floor polish and it turns wonderful lavender immediately. But that, too,
> will convert back over time.
>
> How I can tell that the speed is slower in this moistened area is that
> when
> the tonal palette finally dried and after 24 hours went to the deeper
> thalo
> blue, that area is also blue but paler in tone throughout the steps that
> the
> spot covers. It was on the edge of the print where the excess cyanotype
> solution must have leached back into the center more, without my seeing it
> by eyeball.
>
> So I think you may be talking about humidity being a speed benefit (for
> sure
> in pt/pd, maybe in cyanotype) vs. uneven moisture, which is not.
>
> The humidity thing with cyanotype: here humidity ranged from 58%-77% over
> the last several days. As I waited the exact time between coating and
> exposure with each of my tests, I can compare those and see if that range
> is
> an effect (it was not) but the real test will be when I return to Montana
> in
> August and have 20% humidity there and do the whole testing process again.
> Until then, I cannot tell whether humidity increases speed or not (as it
> does certainly in pt/pd) as I only have a limited humidity range in the
> high
> values here. It may be that cyanotype responds the same as pt/pd with
> this
> variable.
>
> I remember testing the old adage about gum being insensitive when wet. It
> isn't. But I guess it boils down to how wet is wet, or at what point does
> too much moisture create a loss of speed, but some moisture increases.
>
> It could be (my guess from gum) that two variables that have great effect
> on
> alt processes are humidity and acidity/alkalinity. A "fast gum" may be an
> acid gum, etc. etc. blah blah blah.
>
> One more thing I learned: I forgot I had put hydrogen peroxide in my
> development bath, and developed a test print immediately in that (in other
> words, first development bath had hy per in it, it wasn't added after the
> 15
> minute development) and I lost a stop and a third of speed. So not only,
> in
> my book, is hy per unnecessary, but unless you need a loss of speed it
> should never be in the water. What is so odd about hy per is that my
> finger
> was wet with the hy per water bath, and I just touched another wet
> cyanotype
> print, and that miniscule amount of hy per on my finger immediately
> darkened
> the print. And that is a dollop of 20v hy per in a huge bathtub of water,
> so I'm not talking a lot.
>
> Trevor, I'm getting a brilliant blue only waiting 20 minutes after coating
> to expose. Have you tried Arches Platine?
> Chris
>
> ----- Original Message -----
> From: "Loris Medici" > I always thought that the lavender color is
> connected
> to the alkalinity of
> > the paper. The more alkaline the paper, the more lavender color you get.
>
> > In my understanding the speed should be faster when the "paper" is more
> > moistened - because more iron(III) ions are free to act as a sensitizer.
> > The
> > constast also should be lower - because the emulsion is more sensitive
> to
> > light. And if the paper is more dry then there would be less free
> > iron(III)
> > ions, therefore less speed and more contrast.
Received on Sun Jun 5 19:07:36 2005