From: DCHAS Membership Chair <membership**At_Symbol_Here**DCHAS.ORG>
Subject: [DCHAS-L] Photographic chemical baths
Date: Sat, 27 Apr 2019 13:01:49 -0400
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU>
Message-ID: FE49205A-663D-4D2C-8408-4AE3D34CC1DC**At_Symbol_Here**

From: Monona Rossol
Re: photographic chemical baths --new thread

Help!!! I‰??m currently going over the SDSs for about 30 different photo chemical products to try to figure out what comes off each bath of mixed chemicals in the darkroom both when resting and when reacting to the carryover as the print is moved from one bath to another. This project is one in which air filtration is proposed to clean the air well enough to recirculate and exhaust at street level. I only need to find out if this can, or can‰??t, work. But to do that, I really do need to know what to test for down to even nuisance or irritating odor levels.

Several different photo chemical process are used including black & white, selenium and sepia toning, tank film processing, and a bunch of historic processes such as cyanotype and gum printing. In the Black and White products alone there are 7 different developers used for different types of work plus 2 to 4 different fixes, stop baths and washes.

I‰??ve thumbed through the thousands of pages in Mees Theory of the Photographic Process and other classic tomes. They are exquisitely focused on the minutia of the silver reactions and it is only incidentally that I can use these books for generation of airborne chemicals.

A few things are clear. If the developer is one that uses ammonium thiosulfate, the reaction with the silver halides in the print will produce ammonia and sulfur dioxide (especially when the print is in an acid environment from the fix). The sulfite preservatives (mostly sodium meta bisulfite) in almost all the different baths also will release sulfur dioxide. And some of the processes have a formaldehyde (or other aldehyde) hardener. So for sure I need to test for ammonia, sulfur dioxide, acetic acid (stop bath), and formaldehyde (aldehydes).

Now it gets worse. The paper or film contains silver bromide, iodide and perhaps chloride. AgBr is the primary chemical. Can the bromine ion released on development create small amounts of hydrogen bromide and/or bromine gas? If hydroquinone is the developer, looks like HBr is produced. Or will it react with other bath components? One of the developers also contains ammonium bromide as an ingredient.

Then there are a host of other chemicals in these products: phenolic compounds which appear to be part of that ‰??darkroom odor‰?? and imidiazole which may release amines, and many more. One of the toners clearly will release hydrogen sulfide.

If you have any personal experience, suggested reference books, or studies, all would be deeply appreciated.


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