rurmonas@senet.com.au
Date: 12/16/02-09:23:42 AM Z
Quoting Sandy King <sanking@clemson.edu>:
> I appear to be very fortunate in my working conditions with both VDB
> and kallitype in that the tap water at my house is almost always
> neutral or slightly acidic so that I rarely ever see any stain on the
> paper and clearing is visually always 100%. I have been checking the
> pH for a long time in my carbon work and it is curious that high
> alkalinity is a problem with that process as well.
Just in case it was not clear in my previous description,
there are two effects causing the iron hydroxide. One is
a paper "staining" effect. This is due to a reaction with
the paper. This can be seen as dirty highlights, or in the
masked edges of the print. The second is exposure related
(reaction with the ferrous state of the iron) this is
proportional to the exposure, and so is masked by the image
colour. This is more of a problem as it can not be seen.
Using straight FAC and washing the exposed paper in my
slightly alkaline tap water, I can create a yellow-brown
image. This is what "hides" behind the normal image.
Interestingly with a cyanotype this gives a much darker blue
due to the yellow "backing" of the blue image. Hence a badly
processed print can actually have a visually darker Dmax.
Richard
--- Richard Urmonas rurmonas@senet.com.au ------------------------------------------------- This mail sent through SE Net Webmail http://webmail.senet.com.au
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