View Full Version : Fogging of paper

Hans Berkhout
5-Jun-2016, 08:17
Sometimes when printing a cropped negative, part of the image will be inadvertently printed on what should be the white border of the print. I never had a problem removing such result of carelessness. Repeated cycles of potassium ferricyanide followed by fixer always removed the unwanted image, leaving me with a white border as desired. Recently after a printing session I had to go through this procedure again, and to my surprise the treated border area of the print was much whiter than the non treated remainder. I applied the same bleaching procedure to a few other print borders and again the treated areas were much whiter than the non treated. In other words the paper was fogged. This was a box from my freezer, Forte paper, 10 years old. I had always blindly counted on paper remaining "fresh" when stored in a freezer. From now on I'll do the bleach test every now and then on paper that has been in my freezer more than say 2 years.
I'd be interested in learning the experience of LF forum members who keep paper in their freezer. I encourage testing and posting results, including age of the paper.
If fogged, throw it out? Send it to Ginette? Try it with benzotriazole added to developer?

Jim Noel
5-Jun-2016, 08:39
Depending on the chemical structure of the emulsion, film and papers can be victims of chemical fog even at low temperatures.

Doremus Scudder
6-Jun-2016, 07:09

The main culprit is cosmic rays; they'll get into your freezer pretty easily. Modern papers without cadmium in the formulation tend to fog earlier.

To test for fogging, in total darkness or under tested safe safelight tear a sheet of paper in half (or make a couple of test strips). Develop, stop and fix one strip in fresh chemistry; the other strip only gets fixed. Afterward, compare the two. If the paper is not fogged the whites will be the same; if the paper is fogged, the developed strip will be darker.

There are a couple of ways to deal with fogged paper. The first is to add bromide or BZA to the developer. I use a 2% BZA solution or a 34% bromide solution, since I have these on hand. Start with about 1ml per liter (of either or both in combination to control image tone), the exact amount is not that critical. Increase in the same increments till your fog test shows fog has been prevented or until you've added 10-12ml. (Or, if like many you use a 1% BZA solution and a 10% bromide solution, start with 2ml/l and stop at about 20-25ml/l.) The object is to keep the restrainer/antifoggant to a minimum.

Another way is to bleach back the whites using a weak ferricyanide bleach. I use a ferricyanide/bromide rehalogenating bleach, but weak Farmer's reducer will work too. I like a 0.1%-0.5% ferricyanide solution to start with; I've had instances where a 1% solution bleaches to quickly to easily control. Keep a bleached border or fixed only test strip of the same paper handy for visual reference and pull the print just before the bleaching has gone to full paper white. Best is to have this be part of your printing work-flow, since you can the base exposure/contrast on the bleached test prints. However, I've had good results saving some prints inadvertently made on fogged paper this way too. Just be careful not to bleach so far as to alter the tonalities in the image itself. If, like me, you trim your prints and dry-mount, then you can often get by with just localized bleaching of the highlight areas, since the other areas aren't affected so much by a little bit of paper fog.

Hope this helps,


Bruce Barlow
6-Jun-2016, 12:26
A number of years ago, I found that even new papers were slightly fogged, especially the cheap RC stuff I got for proofing. So I started using a little Benzotriazole in my developer to keep my whites white without harsh bleach. Worked fine, except my load of Benzo was mixed entirely in alcohol, rather than just adding a little bit to help it dissolve. fortunately, I had a strong exhaust fan and a good airflow, and only got high on art.

I just finished setting up the new darkroom, and tested one of my papers after it was stored in sketchy conditions for 4 years. No fog. None. Go figger. I'll test my other papers as I set out to use them.

Suffice to say, Benzo is my friend.

Hans Berkhout
26-Jun-2016, 06:09
Thank you all for the helpful feedback. I'll test for chemical fog more often, and deal with it when it's present.