There is a lot of information about contact printing on silver paper here:
Then click on "Azo." Several articles there. And on the Azo Forum there is more information than even I can assimilate.
The new Lodima paper is the best paper for contact printing silver prints. It has the deepest blacks and the longest tonal range, and is significantly easier to print on than contact printing on enlarging paper.
Some may think I am not being objective, since I have had the paper made and I sell it, but as someone else suggested, see all threads about Lodima paper to see what others have to say.
Michael A. Smith