Liam Lawless (lawless@vignette.freeserve.co.uk)
Thu, 28 Jan 1999 23:43:48 +0000
Hi Cor,
As suggested in Post-Factory #, I am now using glyoxal as it is less toxic
than formaldehyde, which I was using before. It is true that most film
emulsions are now hardened in manufacture, but they still benefit from
hardening after processing; developing solutions are alkaline, and
alkalinity "removes" any hardening they have previously been given. I find
that APH scratches very easily and like to give it all the protection I can.
I've come across films that are worse than APH in this respect, but also
better films. I don't know if glyoxal hardens as effectively as
formaldehyde, but I do know that APH negs still need to be handled with
great care even after hardening. Or maybe I'm just ham-fisted?
What Dave says about hardeners reducing the solubility of gelatin is true,
but it also makes it physically tougher - not a great deal, perhaps, but
alt. negs are subjected to a lot of handling. But a point to remember is
that hardeners affect only the gelatin in a film (i.e. the emulsion side)
and do nothing to toughen the base side which remains fragile.
Redevelopment in PMK is complete in maybe 7-8 minutes as far as I can tell
by watching in the dish, but I want to be certain that it is complete. You
may recall that about a week ago, Sandy (it was Sandy, wasn't it?) reported
some tests where he redeveloped for 5, 10, 15 and 20 minutes. I can't find
his message now, but I think there was a significant increase in density
between 10 and 15 minutes redevelopment, and virtually none between 15 and
20 minutes. I believe that the very small difference between 15 and 20
minutes is due to extra staining, and not extra development.
One other point I forgot to mention in my posting yesterday (which I am sure
I do not need to add, though I will anyway!) is that plain hypo or a
non-acid fixer should be used after redeveloping with PMK. An acid fixer
removes the stain; depending on the time, some density may still be gained,
but not nearly so much.
I'm doing my best to complete tests for posting more on this subject on
Saturday, but it's all taking longer than expected. Unfortunately, I
sometimes have other things to do as well (eating, sleeping, occasional
washing... )
Liam
-----Original Message-----
From: Cor Breukel <cor@ruly46.medfac.leidenuniv.nl>
To: alt-photo-process-l@sask.usask.ca <alt-photo-process-l@sask.usask.ca>
Date: 28 January 1999 10:54
Subject: Re: Pyro redevelopment & Hardening
>On Wed, 27 Jan 1999, Liam Lawless wrote:
>
>Hi Liam;
>
>I am not sure if I understand the steps oulined below. You first process
>your negatives "normal", and harden afterwards? I thought hardening of
>negatives with modern emulsions was not necessary. On the whole I do not
>fully understand the term "hardening". I thought that hardening of
>negatives was ment to make them more resistant against scratches etc.
>Wheras hardening (with Glyoxal after gelatine sizing is ment to preventing
>consumption of the organic gelatine by micro-organisms. Seems to be
>different purposes...
>
>
>> wedge, I've only played with a few reject negs so far, but my
>> processing sequence following redevelopment is as follows:
>>
>> 1. Wash, running water from cold tap, about 5 mins.
>> 2. Non-hardening fix, about 2 mins (only because I have no hardening fix
on hand).
>> 3. Wash about 10 mins.
>> 4. Hardening in 4% glyoxal, about 3 mins.
>> 5. Wash, about 3 mins.
>> 6. Final rinse with wetting agent & dry.
>>
>
>>>4. Redevelop in normal strength PMK, 15 mins. at
>
>I also used redevelopment with Pyro; but I never used such a long
>development. When I immerse my bleached negative in Pyro (Laban formula,
>about 1,5 times stronger than "normal"); the image "shows up" pretty fast,
>and after a couple of minutes there isn't no visible cahnge. Probably I
>should take a better look at it, somehow I thought that re-development is
>much faster than development..
>
>
>Cor Breukel
>
>http://ruly70.medfac.leidenuniv.nl/~cor/cor.html
>"The Infrared Gallery"
>http://ruly70.medfac.leidenuniv.nl/~cor/ir-gallery.html
>
>
>
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