1. The other day I attempted to print on Polymax IIRC in the above chemicals and the midtones came out seriouly mottled in freshly mixed developer and rapid fix. I ruled out that I had mistakenly mixed chemicals or hadn't cleaned trays properly, because I successfully printed on Ilford MGRC and FB papers for the rest of the night. Any Idea what happened with the Polymax?[/I]It's unlikely, but perhaps a bad batch of paper? More likely is that this sounds like unueven development. Let the print develop to completion, say something like around 3 minutes or so. Make sure it doesn't float up to the top, or better yet, develop it face down. If the chemicals worked for the Ilford paper, they will surely work with the Kodak paper.
2. Last night, after successfully printing a negative to MGRC, I decided to have some fun and print to MGRC warmtone for the first time. Using the same exposure, f-stop and contrast filter for the warmtone I came up with an underexposed print, about two stops/zones short. I was able to get the print I was looking for by opening the aperture one stop and doubling the exposure (a little less than double to be exact). I couldn't find anything in the pamphlet in the pack of paper to say that there was ISO change between the papers. What happened?
Different papers, even from the same manufacturer, can be quite different in terms of speed. This can be quite pronounced if you are using Kodak's filters on Ilford paper and vice versa.