Washing positive blueprints

Andrea Reichert <areicher [at] cca__qc__ca> writes

>... Though Prussian Blue is insoluble in water, and somewhat resistant
>to immersion, it is still standard practice to avoid washing
>blueprints due to the possibility of fading.  I would be interested
>in hearing from others who have washed positive blueprints in the
>past and the long-term side effects it has had on the line image
>itself.  Any advice would be most appreciated.
itself.  Any advice would be most appreciated.<

You may want to check, whether the positive blueprint was made with
the regular cyanotype process (by exposing a negative to the
cyanotype paper) or the direct-positive Pellet process. In the
(rare) Pellet version, the pigment is embedded in gum arabic, which
may or may not be hardened enough to withstand the washing. In any
case you should avoid alkaline pH of the wash water. A very small
amount of hydrogen peroxide in the water may even restore some of
the blue color.

Klaus Pollmeier


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                  Conservation DistList Instance 16:34
                 Distributed: Friday, November 22, 2002
                       Message Id: cdl-16-34-012
                                  ***