[pure-silver] Re: OT-- chroma list


----- Original Message ----- From: "Stein" <rstein@xxxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Saturday, February 25, 2006 4:23 PM
Subject: [pure-silver] Re: OT-- chroma list



MessageDear Dave,

Today's posting on the Pure Silver - Chroma list concerns enormous good fortune with a sting in the tail.

I bought a cubic yard of Jobo tanks from a eBay sale last month. They are the 2500 series and were used to run B/W processing in a Sydney commercial lab. I guess most of them were used in the rotation mode, but 3 seem to have been set on end and used as deep dip tanks or washers. Hard to say, but the end result on the roataion ones has been a silvery-black deposit on the interior of all the components while the vertical ones have a spectacular encrustation of old fixer on the outside.

I have wiped most of the silvery gunk from the tanks but wondered if minute residues will affect their use in a C 41 process. Any ideas, people?

And as for the fixer crud - I think the tanks will be fine if I can get it off. Will conventional acids like hydrochloric or sulphuric do it or do I need to go more exotic?

    Uncle Dick

Plain household bleach should remove the fixer. Silver can be removed by a dichromate or permanganate bleach, both of which require sulfuric acid to make up. Some silver deposits are very difficult to remove and must be scrubbed off using something along the lines of a stiff toothbrush.
Mild silver stains can sometimes be removed by strong Farmer's Reducer or by using a bleach made up of film stength rapid fixer with about 15 grams per liter of Citric acid added.


Kodak TC-1 Tray Cleaner
Water                            1.0 liter
Potassium bichromate            90.0 grams
Sulfuric acid, concentrated     96.0 ml

The usual warning, add the acid slowly to the water to avoid heating and splattering.
This solution can be re-used until it stops working.


Kodak TC-2 Tray Cleaner (Especially recommended for removal of silver stains)
Solution A
Water 1.0 liter
Potassium Permanganate 5.0 grams
Sulfuric Acid, concentrated 10.0 ml


Solution B
Water                            1.0 liter
Sodium Bisulfite                10.0 grams

Sodium Metabisulfite will do.

For use pour A into the tray and swirl around for a few minutes. Then pour out and rinse with water. Then pour in Solution B to remove the stain left by the Permanganate, then pour out and wash thoroughly.


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


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