From: Bob and Carla (bb333@earthlink.net)
Date: 06/22/02-04:18:31 PM Z
Sam,
Do the scan before you bleach!!! The scan is capable of capturing
amazing scale....it will give you more to work with for making a new
negative, than with any photochemical direct printing process. Then if
you do something irreversible in the bleaching, you will have
preserved an extremely malable image for later options! Good luck!
Robert
S Wang wrote:
>
> Liam and Chris,
>
> Thanks so much for the info! It's just what I needed!
>
> And Mark apparently was extending an open invitation for me to use
> his Imacon scanner (it does a fantastic job with negatives up to
> 5x7!). So I'll try the chemical methods first, knowing that I can
> always ask Mark (and Photoshop) to rescue me if I screw up.
>
> Sam
>
> >Sam,
> >
> >With hydrochloric acid, dichromate bleaches silver to silver chloride, which
> >is insoluble and redevelopable (as in chromium intensification). With
> >sulphuric acid, the product is soluble silver sulphate that just goes into
> >the solution, which is why it's used for reversal. Pot. ferri. bleaches to
> >silver ferrocyanide, which can also be redeveloped, but it's very slow; it's
> >usual to add some pot. bromide to speed things up... the result is then
> >(insoluble) silver bromide. Any bleach giving an insoluble silver salt
> >should be usable for negative reduction by bleaching and redevelopment.
> >
> >After bleaching, you need to redevelop or fix (or tone) for a stable result,
> >since silver chloride, bromide, etc., are light-sensitive. A good way of
> >reducing dense negs is the process known as *harmonising*, whereby you
> >bleach fully in (e.g.) pot. ferri + pot. bromide, redevelop less than
> >completely so that you get full shadow detail with reduced highlights, and
> >then fix. The image will lighten more or less in the fix, and it takes a
> >little experience to judge just how far redevelopment should go. For
> >redevelopment, a print developer is probably best... conventional wisdom is
> >that developers containing a high proportion of sulphite (e.g. D-76) may
> >dissolve some of the silver salts before they can be redeveloped, but I
> >can't say I've noticed it.
> >
> >
> >Liam
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