Re: Is Na2 that sensitive?

Hello Clay,
   
  Thanks for your insight on Na2 concentrations in your process.
   
  I ran a quick print test tonight. I brush coated paper (Platinotype white from B&S) using 1.7mL of FO + 1.5mL of Pd sol'n #3 + 7 drops of ~1% Na2 solution (from a serial dilution of the 20% from B&S). My thinking is that if I keep the number of drops high, then the drop sizes (and amount of Na2 delivered) will average out.
   
  I also coated another sheet of the same paper with the same brush & the same chemistry but without any Na2.
   
  I exposed both at the same time using a 101-step tab & Mark Nelson's Tonal Palette in my Nuarc 26-1K.
   
  Both prints showed tonality all the way down to the B=0 square (R=0; G=255), so I'm concluding that 7 drops of 1% Na2 is too little contrast agent and my previous concentratio of 3 drops of 20% Na2 is too much. I'll test again at an intermediate concentration.
   
  Sincerely,
  Mike
  www.ExpsoeTheShadows.com
   
   
   
   
   
   
   
  

Clay <wcharmon@wt.net> wrote:
  This is one heck of a lot of Na2 for these volumes. I am using 1 drop of 2.5% Na2 in the same sensitizer volumes for my digineg work. I would cut this stuff 1:7 (2.5%) and just use a drop or two of that strength.
    On Nov 29, 2005, at 11:00 AM, Raven Weiss wrote:

    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 sufficien t 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 availab le 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 th e 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 Wed Nov 30 02:12:51 2005