Dichromate bleach clearing bath formula

[James McClean]

I am vexed as to why D. Wood's clearing bath DW-1 as published in Anchell's 3rd edition of the Darkroom Cookbook goes so far off script from Kodak CB-1 which is simply 90g/L sodium sulfite. Metabisulfite is recommended by Dietrich for use with permanganate bleach. Anchell's text mentions to use the permanganate bleach and metabisulfite clearing bath formula listed below, but they are not listed, anywhere in the 3rd edition that I can find. Why the addition of boric and citric acid in DW-2? Other than these minor constituents, DW-2 closely resembles Legacy Pro Hypo Clearing Agent if diluted 1:1 from the stock solution. I assume the small amounts of trisodium citrate and disodium EDTA are water softeners in Legacy Pro formula.


We often hear the advice to use metabisulfite clearing bath with permanganate bleach. Enough said on that topic, how about the other side of the equation. What affect does metabisulfite have as a dichromate bleach clearing aid? Is this a typographical error in Anchell's third edition?

 

[James McClean]

Mohmad,
Thank you for your reply, however to clarify, my question is not about permanganate bleach. Enough has been said on that topic. Allow me to rephrase my question for clarity.

Does anyone use David Wood's DW-2 clearing bath formula as published in the 3rd edition of the Darkroom Cookbook with dichromate bleach or know the reason for recommending metabisulfite in combination with sodium sulfite, boric and citric acid for use with dichromate bleach? I have to assume the recommended DW-2 is a clearing bath for dichromate bleach since it follows DW-1 dichromate bleach formula, especially as it has been long established that permanganate bleach should not contain sodium sulfite. This is the only instance I have seen recommending a dichromate bleach clearing bath containing both sodium sulfite and metabisulfite. And the boric and citric acid? What role do they play in this reaction?

Let's please keep replies on topic of dichromate bleach and the DW-2 formula. If someone doesn't' know a specific reason for David's formula, then nothing further need be said. More than enough has already been said elsewhere about permanganate versus dichromate bleach.

 

[Raghu Kuvempunagar]

What affect does metabisulfite have as a dichromate bleach clearing aid?

Metabisulfite (or bisulfite) is not advised for dichromate bleach. Here's the technical reason as given by Grant Haist in Modern Photographic Processes Vol 2:

"A solution of sodium sulfite is customarily used to remove dichromate and the products of dichromate bleaching, as these compounds are almost completely soluble in the sulfite solution. These compounds become less soluble as the pH of the clearing bath is lowered. A sodium bisulfite clearing bath is thus not a satisfactory clearing solution following a dichromate bleach."

Mohmad,
This is the only instance I have seen recommending a dichromate bleach clearing bath containing both sodium sulfite and metabisulfite. And the boric and citric acid? What role do they play in this reaction?

These chemicals are used to reduce pH of clearing baths that have a high concentration of sulfite. Here's Haist's explanation on why that's a good idea: "a high sulfite concentration acts to solubilize silver halide, thus lowering the density of the image produced by second development. The use of a sulfite-bisulfite solution produces a solution with a lower pH and less attack upon the silver halide."

Further, Haist writes: "If sufficient period of time is available for the clearing treatment, a weak sulfite solution should be used. For example, Kodak clearing bath CB-3 is only a 1 % solution of sodium sulfite." This is what I use in my reversal processing workflow.

 

[James McClean]

Raghu,
Thank you so much for this answer, it is exactly the information I was seeking. And thank you also for the reference. I am able to access Haist vol 1 from online libraries and will be looking to track down vol 2.

I will be processing some B|W Positives next week and will run with D. Wood's recommended bleach and clearing bath formulae. Thank you for the assurance that the clearing bath formulae DW-2 is indeed compatible with dichromate bleach.

Cheers!
James McClean