Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Sat, 30 Jan 1999 19:27:39 -0500
David Kern wrote:
>
> I'm making my first #1 and #2 solutions for pt/pd and have three SHORT
> questions.
>
> 1) Is oxalic acid useful/necessary? I understand it may promote longevity
> of the solution and increase contrast.
>
> 2) Can potassium chlorate be kept in a separate solution from the #2 and
> added when sensitizing the pt/pd?It was mentioned in a thread a week or
> so ago but it was not clear what concentration solution to use.
>
> 3) What are some other contrasting agents and methods of application?
> Does sodium dichromate work in an ammonium citrate developer the same as
> in potassium oxalate? Does it cause less grain than potassium chlorate?
>
I confirm the answers from Eric Neilsen.
I would add the not only can the K clorate solution be kept separate, it
SHOULD be kept separate from coating solutions. Any oxidizing agent (or
contrast agent for this process) should be stored separate from stock
and working coating solutions and should be only added when mixing the
coating "soup". Add one drop of a 0.25% to 2.0% solution for an 8x10.
Problems could arise which would degrade the solutions it is added to.
I use potassium dichromate, and have used it in the coating "soup", and
developers (both potassium oxalate and ammonium citrate). It works with
ammonium citrate similar to potassium oxalate. There are some noticible
differences whether it is used in the "soup" or the developer; not as to
contrast control (that's about the same) but in varrious qualities of
the image. Try varrious images (and subject matter) both ways and
compare. When adding to the "soup" try Adding one drop of a 0.1% to
1.0% solution for an 8x10.
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/
This archive was generated by hypermail 2.0b3 on Sat Nov 06 1999 - 10:06:48