These are my observations after four sessions with the Mordancage process - I will not describe the process as it is well described in an artical on unblinkingeye. I used the chemistry listed in the referenced artical - there are other chemistries - a good discussion is found at http://www.usask.ca/lists/alt-photo-process/ listing other chemistries and techniques. So here is what I found. You can do it with RC paper but the results are not very pleasing (to me) - there is much more activity with a good byarta base FB paper. I used a variety of fixed and dried prints focusing on contrasty subjects with lots of detail. My first go at it was pretty good - three of my prints are in my gallery. http://www.apug.org/gallery/showgall...500&ppuser=466 The darkest areas boiled off leaving white were the deepest blacks were. Because I am using 35vol H2O2, I was warned that there might be some yellowing. This lightened up a lot afer a good fix and a good wash. The smell is bad - I used my garage. I tried using a safelight and regular lighting and noticed no difference. (Except in the session where I used the process on unfixed prints)
The process has capabilities for both the patient and the impatient. I pursued the impatient path. The veiled effect doesn't excite me yet so I didn't soak for long periods hoping the emulsion would lift away and replant as a veiled distortion. The other choice is the length of wash time. Washing long periods will keep from killing the developer and will reduce staining of FB prints - on the other hand - having some acid in the emulsion when redeveloping caused a greater lift on the deep blacks. Since I planned on keeping all my chemicals one shot - I didn't opt for the long wash time and went ahead and let the process become more active in the developer. It makes a mess - black slimy globes floating around everywhere. - I also realize that some slight yellowing is likely unavoidable. Developers that worked were PC-TEA and AGFA Multicontrast - Amidol DID NOT WORK in this process - I recon any D-72 / Dektol variant would be fine.
For images that are contrasty & moody but lacking - mordancage will turn the blackest areas white rendering a negative/positive image. For a one pass process - the look is spooky but not completely altered. When the process is repeated - it leaves the emulsion thin and the entire image becomes light. Selenium toning did not help as it turned the grey image brown without intensifying it as I had hoped it would. The big success is for images that will benefit from a more sublte alteration.
I also tried unfixed images. I pulled them from the developer - washed them and put them in the mortant solution. The reaction was poor. Some have written that the chemical does't displace the water in the emulsion very quickly or very well and that limits the activity - my experience would bear that out. After the deep blacks began to deteriorate, I flashed the paper and it went negative and lith. The negative would be ok but I over exposed it. I looked at the effect and decided that the more subtle results gave me more of what I was hoping for.
So for all my exploration - what I tried first worked best - using the right image (whatever that is) on a finished print (dry) washing well after the mordant but not for longer than 4 minutes or so - such that some acid is still in the image when it goes into the developer. I used my gloved finger to rub off the lifted areas. - I did re-fix - some have mentioned that there are advantages to allowing the print to dry after the redevelop to let the silver oxidize before fixing - I have not yet tried that. Moving forward as I work in my darkroom - there will now be images that I make extras on with the idea that they will make good candidates for this process - It also adds a second chance for finished images that are lacking (I don't think I am the only one with a stack of these somewhere) So - I recommend this to you adventurous ones.