Identifying print

I have a book with several small maps and illustrations on blue
paper. The imprint is: Annual Report of Colonel B.H. Grierson, 10th
Cavalry, Commanding, Department of Arizona, 1889. The maps are on
white paper, 'cover weight' with a cobalt blue coating on the recto.
The images and text appear 'etched' and show up as white on the blue
background, although the white is more of a light blue. The verso is
white with bluish residue as if coming from the recto. The paper
does not seem to be brittle.

I would appreciate any insight on the chemical nature of this
printing process, and how it might be best preserved.

Scott K. Kellar
Bookbinding and Conservation


                                  ***
                  Conservation DistList Instance 21:59
                   Distributed: Saturday, May 3, 2008
                       Message Id: cdl-21-59-028
                                  ***