I am about to try some cyanotypes having restricted myself to salt prints previously. I am wondering;_
1) How archival are cyanotypes? I know that old engineering 'blueprints' have lasted well but I am wondering how long it might be expected to keep a cyano on a wall and still look good. (Ignoring the obvious location/siting of the print into account)
2) In that respect, does toning/staining make any difference to their keeping property or is it purely an aesthetic quality?
3) And when toning/staining I guess that the whole substrate is stained or is it possible to colour only the image?

Thanks for any replies.