Re: cyanotype staining

On Sat, 22 Nov 2003 08:54 am, ryberg wrote:

> The unexposed borders and to a lesser extent the highlights, retain
> the yellow stain from the sensitizer and nothing, even overnight washing,
> seems to remove it. For some prints this doesn't matter much but it is
> pretty ugly on others.
> The difficulty of coating makes it impossible (at least for me) to
> limit the coating just to the image area--in fact, I have to over coat an
> inch one each side and trim that inch off due to irregular drying at the
> edges.
> I don't know whether the stain is from the ferricyanide or the FA
> citrate or both) any suggestions?

This sounds typical of the stain I have seen from some papers.
I am not sure of the exact chamical process, but I think it is a reaction
of the FAC with something in the paper which produces a yellowish
coloured iron compound. It appears to be insoluble in water so washing
does not remove this stain. The only cure I know of is to try a different
paper.

Richard

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Richard Urmonas