I am using Fuji single emulsion mammo x-ray film for enlarged negatives. I have done this successfully with making an interpositive first etc and using paper developer. I just tried to use an actual print as an interpositive as I have heard of others doing this. Everthing comes out as a perfect positive! I am developing in D-55 4:1 and exposing in a contact print frame under a 300w bulb at about 30in. its totally weird! I have tried exyending exposure and decreasing to ridiculously low and its always a positive! Could it be my developer? I don't know.