[pure-silver] Re: PMK


----- Original Message ----- From: "Jim MacKenzie" <jim@xxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Thursday, April 27, 2006 3:49 PM
Subject: [pure-silver] Re: PMK



----- Original Message ----- From: "Hagner, Andrew" <Andrew_Hagner@xxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Thursday, April 27, 2006 4:39 PM
Subject: [pure-silver] Re: PMK


Other than for use with PMK, what are the advantages (if any) of an all
alkaline process for film development.
===
You need a much shorter wash and can forego a hypo-clearing agent step.

Alkaline-fixed film needs about five minutes of wash to be archivally processed, without any washing aid needed.

Jim
Actually about ten minutes. While wash rates are faster the sulfite wash aid has a specific ion-exchange action that a simple alkaline bath or alkaline processing does not have. Wash times for film using sulfite is about 5 minutes regardless of the type of processing used.
Using an alkali has no advantage over a bath that makes the film neutral. Neutral pH fixing baths can be made using Thiosulfate and sodium sulfite. They work fine. If enough sulfite is added it will tend to prevent staining from carried over developer. A plain fixing bath needs about 5 grams per liter of sulfite but this can be increased to around 15 grams per liter for stain prevention. Adding carbonate, Borax, metaborate (Kodalk), etc, really has no advantage.

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

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