I made some extra silver-gelatin prints from my session last week knowing I would try out a few more 2nd pass lith prints. Basically you use a bleach on the silver-gelatin print as far as you care, then re-develop using lith developer, fix and wash as normal.
My first print was using Ilford MGIV RC paper, which gives a pinkish tone when doing this 2nd pass lith printing. I first have a similar print which is not bleached or re-developed.
I should probably over-expose the prints a bit more when doing this process, as the bleach and re-develop process never gets quite to the same tonal range as the original. But I like the subtle color of the 2nd pass lith better than the original. This particular paper seems to go towards a brownish-pink with this technique, which I find quite pleasing. My other experiment with this technique was with the same paper and similar results, despite being a near-IR film (Ilford SFX 200).
My second print I used Ilford warmtone RC paper, which I had read would result in more dramatic tones but (I think) because my developer was at room temp rather than higher temp, resulted in fairly muted differences. First the straight silver-gelatin print.
In this case the 2nd pass lith went a bit purplish rather than pink and got darker with the re-development. But I definitely didn’t get the bold colors some have suggested, perhaps because of temp of developer or even age of developer (I only put a couple prints through).
I find the 2nd pass lith printing process to be quite enjoyable since I can have a silver-gelatin print that perhaps is not ‘perfect’, and put it through this process and get a better result than the original.