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Photography Question 
Kim E. Martin
 

Black and White Printing


Does anyone know what makes prints yellow on the edges of your paper when making black and white enlargements in the darkroom? Fixer? Developer? Any thoughts are appreciated. Thanks!


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9/20/2006 11:00:19 AM

 
Andrew Laverghetta
BetterPhoto Member Since: 9/13/2004
  I would guess it would be the fixer. Are you fixing for the whole time? What kind of paper are you using, Fiber Based or Resin Coated? Could your fixer be exhausted? If you have an undeveloped slice of film that you might have cut off while loading film to be developed, you could throw it in the fix, find out how long it takes to clear up and then fix for about twice that amount. I think that's how it works. Or use hypo check. It comes in small bottles which are suprisingly expensive for how much you get. When in doubt, fix longer than you think you should. Also rinsing for the recommended time could be part of it. I believe old paper will also yellow as well.

Hope this helps!

Andrew


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9/20/2006 9:20:53 PM

 
Alan N. Marcus   Dear Martin and Andrew,

The standard layout for developing (processing) print paper is:
Developer (always an alkaline solution)
Acid Stop Bath (dilute vinegar solution (acetic acid)).
Acid Fixer tray
Wash tray

You can skip the stop bath however, its purpose is to stop development dead in its tracks and it protect the fix bath (extents its life) from the harmful neutralizing effects of the alkaline developer.

The developer is a reducing solution. It reduces (splits apart) exposed silver salts into their two component parts, silver and a halogen. The silver remains on the paper to form the image, the halogen goes into solution. This action dilutes the developer. The reducing agent has an affinity for oxygen. Spent reducing agents oxidize and become staining agents. The developer contains preservatives to retard aerial oxidation and to neutralize the staining agents.

As the print is moved to the next solution, some spent developer is carried with the paper. Some carryover remains in the stop bath but some continue on to the fixer.

The fixer (hypo) contains a sulfur compound. Sulfur attacks silver over time, and causes it to tarnish and turn brown. A used fixer contains developer carryover with its staining agents. The fixer is a solvent for undeveloped silver salts. When the print paper emerges from a good fixing bath, the paper contains residue fixer. If not completely washed off the staining agents in the spent fixer will stain the paper yellow.

It is necessary to wash the paper (film too) in running water to remove all traces of the fixer. Otherwise, yellow staining will result. Modern papers are over coated with a resin (actually now a poly-plastic and not a resin). This overcoat waterproofs the paper. Since paper is made from wood pulp it has a cell structure that absorbs fluids like a sponge. Without the over coat the wash time will be 1 hour for thick papers and Ĺ hour for thin. Washing time can be reduced to minutes with a suitable pre-wash bath in hypo clearing agent (a salt like solution that neutralizes spent fixer).

The overcoat always violated at the edges when the paper is cut to size. This happens during packaging so you canít do a thing to mitigate this. Spent solutions will be absorbed into the paper from the cut edges. Only copious washing after the fix or use of a suitable hypo clearing agent will prevent yellow edge stain.

Sorry, paper making and chemical processing remains both an art and a science.

Rub-a-dub your prints in a tub.

Alan Marcus
ammarcus@earthlink.net


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9/21/2006 5:57:19 PM

 
Mark Feldstein
BetterPhoto Member Since: 3/17/2005
  Greetings Kim. It could have been too many prints in a tray and they may have just floated together along the edges. One fix, so-to-speak, would be to rewet the prints, refix them and then rewash to see if the stains go away. Otherwise, you're probably outta luck and need to reprint.

In the future, you should always use fixer tester of some kind, even the film strip that Andrew recommended would do fine. And as Alan said, Hypo Clearing agent. Requires an extra tray but really cuts down on wash time and gets hypo out of your prints. To cut down on the entire fixing process too, I prefer using Kodak Rapid-Fixer or some similar fixer from Ilford.

Live and learn ;>)
Mark


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9/21/2006 6:07:58 PM

 
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