Mystery Washing Aid

[yeknom02]

I've started puzzling myself with fixers, so why not fixer clearing agents? I know there are actually a bunch of different washing aids out there, though Kodak's Hypo Clearing Agent seems to be the #1 recommendation. And I also know that every aid goes about eliminating fixer in different ways. I've got a bottle of Zonal Pro archival rinse that I've got to get through before I explore other options, and it says the ingredients include Ammonium Bisulfite and Sodium Hydroxide. The concentrate is mixed 1+62 (2 oz. makes a gallon)

Documentation is scarce, so my questions are:
(1) How long does the diluted solution last (assuming stored in airtight bottle)?
(2) Can I re-use the solution? If so, what's a reasonable number of rolls of film/8x10 sheets of paper before I can toss the solution?
(3) I have a septic system, and the consensus I've read is that disposing of developers is ok given enough dilution, but disposing of fixer is a no-no. What about this wash aid solution?

 

[MattKing]

The B & H listing for the Zonal Pro archival rinse indicates that it is discontinued by the manufacturer, and that it has a capacity of 100 8x10 prints per gallon of working solution (which seems rather optimistic).

One caution about your terminology. Traditionally there were uses for what was known as "Hypo Eliminator" which is a different chemical than "Hypo Clearing Agent". There are actually advantages to leaving a small amount of residual fixer in place - Hypo Clearing Agent does that, while Hypo Eliminator does not.

 

[Gerald C Koch]

Kodak HCA is a mixture of sodium sulfite with a chelating agent and a buffering agent. It is safe for septic tanks. Once used the solution quickly breeds various kinds of mold. Therefore it should not be kept for more than a few days. So its capacity is really not important. It is so cheap to mix you own from scratch that this is not a problem. There is a formula in the APUG archives. Even a plain sodium sulfite bath can be used as a clearing agent.

The ammonium bisulfite and sodium hydroxide in the Zonal Pro product form a buffer. It may also contain a small amount of a detergent which will not appear in the MSDS. Indeed other clearing agents other than HCA use such an approach to facilitate the exit of thiosulfate from the emulsion.

 

[bsdunek]

One caution about your terminology. Traditionally there were uses for what was known as "Hypo Eliminator" which is a different chemical than "Hypo Clearing Agent". There are actually advantages to leaving a small amount of residual fixer in place - Hypo Clearing Agent does that, while Hypo Eliminator does not.

Not saying you're wrong, but I would think that one would want all hypo to be eliminated. What is the reason for leaving a little behind? Does that help the final wash work better? Just puzzled!

 

[Gerald C Koch]

Many years ago Kodak did a study on the effects of residual hypo in the emulsion. It found that image stability was better if a very small amount of thiosulfate remained. I believe they concluded that the reason was a slight sulfiding of the image silver. Agfa's Sistan archival bath worked on a similar principle. It was noticed that gold toning for archival permanence woked even when the gold salt was eliminated from the bath. BTW, Kodak no longer recommends the use of their hypo eliminator HE-1.

Microfilm which has the most stringent requirements for permanence is routinely toned with either a sulfide or a selenium toner.

 

[MattKing]

Not saying you're wrong, but I would think that one would want all hypo to be eliminated. What is the reason for leaving a little behind? Does that help the final wash work better? Just puzzled!

As I understand it, it is a little like silverware - just a little bit of tarnish on your spoons helps protect them.

See this link and the posts therein by Richard Knoppow: http://groups.google.com/group/rec....read/thread/8d4a375581894044/90edccbd49392914

 

[yeknom02]

The question remains of how best to dispose of it. I can't find any MSDS info online, and with Zonal Pro out of business, I doubt I will at this point.

 

[pgomena]

Hmm, it's a dilute solution of sodium hydroxide. I would dilute it further and just put it down the drain. You might mix in a little left-over acid stop bath if you want to neutralize it further.

Peter Gomena

 

[Gerald C Koch]

Hmm, it's a dilute solution of sodium hydroxide.

MSDS's are somewhat misleading. They do not tell you what is in a solution but only what chemicals were originally added to make the solution. In the given example, the ammonium bisulfite and sodium hydroxide immediately react to form a buffer. Since this is a washing aid the resultant pH is probably very close to pH 7, neither acidic nor basic.

There is no problem with tossing the stuff down the drain. Just follow with some water.