Is Na2 that sensitive?

Hello,
   
  I posted this (below) on Mark Nelson's PDN Group, but I'm hoping to get a wider response here at ALT-Photo.
   
  Sincerely,
  Mike
  www.ExposeTheShadows.com

Raven Weiss <ravenweiss@yahoo.com> wrote:
  To: PDNPrint@yahoogroups.com
From: Raven Weiss <ravenweiss@yahoo.com>
Date: Tue, 29 Nov 2005 08:25:45 -0800 (PST)
Subject: Re: [PDNPrint] Is Na2 that sensitive?

Hello Mark,
   
  Thanks for your quick response (below).
   
  Looks like you are using a serial dilution method, which makes sense if Na2 concentrations need to be that precise. Unfortunately, I don't have a pipette, just an eyedropper. In your experience, will it be sufficient for me to serial dilute as you suggest but use an eyedropper if I'm using enough Na2 that equates to a concentration in the middle of Dick Arentz's chart?
   
  Also, if I humidify my paper prior to exposure, will I drive this (film speed of the paper) towards repeatability? Or, will I just introduce another variable? Specifically, the relative humidity is around 10-15%. Does this variability cause a change in paper speed - and, does humidifying the paper to anything above 50% keep the paper speed constant?
   
  I hope I'm making my question clear.
   
  Sincerely,
  Mike
  www.ExposeTheShadows.com
   
  

Ender100@aol.com wrote:
  Mike,

Na2 is very sensitive.... I am not sure how you are measuring, but it is
possible that your problem could relate to that. Have you seen Dick Arentz's
chart for Na2? It is available on his website.

I dilute the Na2 by cutting it with equal parts of distilled water... then I
repeat to get 20%, 10%, 5%, 2.5% & 1.25%. I do this with a pipette.

Also, humidity can vary speed... make sure your humidity and drying times are
constant.

Best Wishes,
Mark Nelson

In a message dated 11/29/05 1:07:37 AM, ravenweiss@yahoo.com writes:

> Hello Folks,
>
> I've used the PDN system with success late last year to produce Pd-toned
> Kallitypes.
>
> Now, I've been trying to create an adjustment curve for Palladium using
> Na2 contrast agent. Finding the correct exposure time was easy. However,
> getting the correct color density choice (choosing the first "paper white"
> square) has been very difficult. I'm getting everything between B=30 and B=70
> (with R=0, G=255) with the same (I think) level of Na2.
>
> Specifically, I'm using 1.7mL of FO and 1.5mL of Pd sol'n#3 and 3 drops of
> 20% Na2. All chemicals are relatively new & clean - from Bostick &
> Sullivan.
>
> The drift in color density choice is causing wide variations in the
> 101-step tonal palette, as you can imagine.
>
> I'm thinking of diluting the Na2 by 10 fold and using 10X of this dilute
> solution - hoping that the variability will average-out and give me
> reproduceable results. Any hints on how else to proceed?
>
> Sincerely,
> Mike
> www.ExposeTheShadows.com
>
>

Mark Nelson
Precision Digital Negatives

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Received on Tue Nov 29 11:03:16 2005