As always when considering the question of permanence the storage conditions
need to be taken into consideration. (My archivally processed silver prints
are for example suffering from mould in the gelatin due to damp storage
conditions - while those less carefully processed seem to last better!)
Recent accelerated fading tests here confirmed a cyanotype to be
significantly less stable to light than either platinum or salt prints.
However there is considerable evidence as stated that they have kept well in
albums for up to 150 years.
Peter Marshall
Family Album/Gay Pride - http://www.dragonfire.net/~gallery/index.html
Also on Fixing Shadows: ----------- http://fermi.clas.virginia.edu/~ds8s
Future Press and elsewhere... E-Mail: petermarshall@cix.compulink.co.uk