From: Vrueh, G.J. de (G.J.de.Vrueh@pve.agro.nl)
Date: 11/22/00-03:46:10 AM Z
Hello Liam,
This is not the awnser to your problem but yust some thougts going trough my
mind...............
I have had a simular experience in the past with another proces, namely with
oil printing.
Without discribing the whole proces what happens is as follows: after
applying a thick caot of gelatin to paper and drying the paper is coated
with a amm bichromate, dried and exposed to uv though a large negative.
After exposure the paper is washed, cleared with metabisulfiet washed and
dried.
After this the paper can be made wet again and the gelatin matrix can be
inked.
After washing i always noticed that there remains a ghost image very light
brownish-grey. This ghost image does not disapear after clearing. It
appeared to me the stain is most appearend were exposure was greatest.
This looks like your problem is such an extend that there where the bleach
works the most (ie where the most silver is removed, the highlights to be)
the stain is most apperent.
In the process of oilprint the galatin is chemically bonded (tanning) by the
bichomate under the influence of UV. I think this also happens when you
bleach(in fact bromoil printing works with this phenomenon. there is also a
ghost image in this proces)). This means that the gelatine hardens and is
harder to clear at that point. Maybe a by product is formed during this
reaction that causes the stain.
I think it is not the support that causes the problem but the thikness of
the gelatine. Altought i have to admit that i do not know weather or not PE
paper has a thinner galatin caoting than FB paper and so i cannot explain wy
PE paper does not have this problem.
Isn't there a bleach with non hardening properties but one thas does solve
the silver image?
Greetings Gerard de Vrueh
-----Oorspronkelijk bericht-----
Van: Liam Lawless [mailto:lawless@ic24.net]
Verzonden: woensdag 22 november 2000 5:05
Aan: alt-photo-process-l@skyway.usask.ca
Onderwerp: Re: direct positive
Hi Taduez,
That was meant to be a private message to Judy and I wasn't aware it had
gone to the list. Sorry everyone!
However, I get staining - grey-brown in what should be the white tones - on
Ilford Warmtone, fibre-base - perhaps plastic papers are OK, but I don't use
them! What I'm trying to do is get reversed prints, not so much for use as
paper negs, but as final images - on Ilford WT FB if possible. My
"brilliant idea" did not work as well as hoped, but I'm also exploring other
avenues.
So, I suspect that dichromate bleach is incompatible with WT FB, and maybe
all fibre base papers. But your remark about omitting the clearing bath is
interesting, and may persuade me to buy some Ilfospeed.
Thanks for your input.
Liam
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