Wayde Allen (wallen@boulder.nist.gov)
Tue, 02 Nov 1999 13:51:05 -0700 (MST)
On Tue, 2 Nov 1999, Carl Weese wrote:
> Wayde Allen wrote:
> >
> It isn't clear to me that the dry gelatin
> > film is greatly affected by this "hardening". Is that really true or just
> > an assumption?
>
> It's real, Wayde. For some reason the well water here in western
> Connecticut doesn't get along with the built-in hardeners in either film
> or silver-gelatin papers. Unhardened emulsion isn't just easy to scratch
> when wet, it's also fragile after drying. You can even see the
> difference between hardened and unhardened film--catches/reflects light
> differently. I'd expect the difference to be less where the unhardened
> emulsion is normal, but the hardening action is clearly there in the dry
> film or paper.
I don't doubt that there is some effect. I am however interested in
knowing how big the effect actually is? I've used both hardening and
non-hardening fixers and can't say that I have particularly noticed any
difference, but then again I haven't been looking or testing for it.
One question that does come to mind is how you are hardening your film and
prints? If you are using a hardening fixer, and as you say the water
nullifies the built-in hardeners, I'm wondering why it isn't also
nullifying the hardening action of your fixing bath? Presumably you also
wash the prints or film with this same water which seemingly would further
exacerbate the problem. I'm not trying to say you are wrong, I'm simply
very curious.
Most such photographic information tends to be anecdotal in nature. How
does one go about measuring the effect of hardening in a gelatin thin
film? Has anyone here actually done it?
> Of course I have no idea if this relates to the hardening
> of gum materials.
I would think that the effect would be similar. However, I think that for
gum printing the primary reason for hardening the (optional) gelatin size
is to make it less water soluble. You don't want the size to wash out of
the paper while developing the print since that would take at least some
of the image with it.
- Wayde
(wallen@boulder.nist.gov)
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