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printech, September, 2000
Re: acid stop bathes and silver recovery


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From:GaryJGATF(gjonesprinting@aol.com)
Date:Thu, 7 Sep 2000 12:52:34 EDT


Sherry: Some Answers to your questions: 1. Acid stop baths are not usually used in automatic processing equipment for the most part these days. However, if they can be used (e.g. manual tray processing) they do help preserve fixer strength. I am not aware of any commercial recycling systems for stop baths. 2. Fix passing through MRC silver recovery is not reusable in a film processor because iron and copper that replace the silver are corrosive and would give problems with the processor. They also would form oxides that would give problems with contamination (specks) on the film and machine parts. Furthermore the need for monitoring remains a major drawback for MRC's; holes in the steelwool are easily created and the system does not work any longer then and would result in fixing problems. 3. The best silver recovery technology for low silver concentrations is ion exchange. These units are typically used for recovering silver from washwater. Most facilities do not combine washwater and fix for silver recovery. They will treat both streams separately, otherwise the volume of washwater will require the use of a holding tank and then a pumping system with timers and this gets to be somewhat expensive. Fix can be treated in batches due to the smaller volumes associated with fix. Typically, washwater and fix are treated as discharged from the processor. This is the easiest and generally most cost effective approach. 4. Acid stop baths will not have any silver in them because they are designed to stop the developing process only. Let me know if you have anymore. Gary Jones Graphic Arts Technical Foundation 200 Deer Run Road Sewickley, PA 15143 412/741-6860 x608 - Phone 412/741-2311 - Fax



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