Paper negatives work wel when made correctly. The tendency is to make them too contrasty. Use a single weight paper, Slavich from Freestyle is the only one I know is currently available. develop in a soft working developer. exposure times with cyanotype will be up to twice as long as for a negative, depending on the quality of the paper negative. My class of 20 student used made these and used them for slat prints just a few weeks ago with very goo success. It is important to have the shadow areas with just enough density to show slight tonality. Since salt prints have a much longer scale than cyanotype, the negaties had to have much more density in the highlights.