[pure-silver] Re: Wash aid


----- Original Message ----- From: <Johnsimage@xxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Monday, February 27, 2006 11:46 AM
Subject: [pure-silver] Wash aid


hi folks,

I'm printing fiber paper and have run out of Hypo clearing agent. I now live
in rural North Carolina, any suggestions for a home brew solution that
could be put together from ingredients in local stores (hardware & grocery).
Cordially,
John Harmon


   Kodak Hypo Clearing Agent is approximately:

Stock Solution
Sodium Sulfite, dessicated            100.0 grams
Sodium bisulfite                       20.0 grams
Sodium Citrate                          5.0.grams
EDTA Tetra Sodium Salt                  5.0 grams
Water to                                1.0 liter

Target pH is 7.0

For use dilute one part stock to four parts water.

If the solution is used one-shot the two sequestering agents are probably not necessary. They are intended to prevent sludging from carbonates in the water and from alum from hardeners.
The buffered sulfite solution has a couple of advantages over an alkaline bath. One is that it preserves the hardening action of Alum hardeners. The other is that Sodium Sulifte has been found to have a specific ion exchange action for thiosulfate and for the reaction products of fixing. Plain alkaline baths do not have this ion exchange effect.
KHCA and similar baths have much more effect on the emulsion than on the paper support of fiber paper. While wash times are shortened they are still much longer than is required for RC paper or film where the support does not absorb and hold the fixer.

The research paper describing Kodak wash aid is:
"The Effect of Salt Bths on Hypo and Silver Elimination", R. W. Henn, Nancy H. King, J. I. Crabtree _Photographic Engineering_ Vol.7: Nos.3&4 (1956) The authors are from Kodak Research Laboratories

The formula was derived from limited data in _Modern Photographic Processing_, Grant Haist, and from the MSDS for Kodak Hypo Clearing Agent.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx







=============================================================================================================
To unsubscribe from this list, go to www.freelists.org and logon to your 
account (the same e-mail address and password you set-up when you subscribed,) 
and unsubscribe from there.

Other related posts: