Response to negs for POP

I've toyed around with salted paper, which is a POP process. Printing out processes do not require development of a latent image - the paper blackens automatically on exposure to light (it still needs to be fixed to make the image permanent though). Yes, POP paper accomodates a much longer density range. The basic reason for this is that the paper is self masking. If you use a contact printing frame, you can see the process at work by opening the back. In the shadows, density will appear readily but the deposited silver tends to slow down the emulsion in these areas by masking the light - this is what is meant by the self masking process. So the shadows take a long time to develop to a good black, which gives enough exposure to the highlights. As a result of this self masking, the paper accomodates a very long density range. Depending upon whether you are going to buy POP versus coating a paper yourself, you might have some room for play. For example, if you're coating your own paper, dichromate can be used to increase contrast a bit.

Now obviously, you getting the required negative needs expansion i.e., overdevelopment. The problem with overdevelopment is that it tends to increase grain. Now personally, I think this whole bit is a little over reacted to because this is a contact printing process - the grain would be more likely problematic with an enlarging process. But the consensus seems to be that overdevelopment does not work as well as it used to. In any case, that is the reason for the popularity of staining developers like pyro and pyrocatechin with such processes. Pyro is a staining developer. So part of the density comes from the stain. Since that is the case, the silver image itself needs to be developed to a lower contrast index, which thereby allows you to avoid the graininess that comes with overdeveloping the silver image. Of course, pyro has a bunch of other advantages also including the fact that it is a sharp developer (creates adjacency effects), makes developing by inspection easy etc. You could buy the necessary powders and mix up the developer if you want. The powders should be easy to take with you. Keep in mind that pyro is quite toxic and use appropriate caution in using it. Having said that, I see no problem with utilizing materials you are familiar with for the overdevelopment. Another option is to buy film and developers you are comfortable with and develop them the normal way. Then make a duplicate negative which is overdeveloped. A couple of advantages to this. One, you can have negatives for each process. Two, you get a little more points of control to tweak the neg for the POP process. You could buy some Kodak SO-132 direct duping film or buy some lith film for making the second negative. Lith film will develop to a fairly high density range quite easily.

Good luck, DJ

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