Re: Chrome alum

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From: F. Wentzel (fotochemiker@yahoo.de)
Date: 12/10/01-03:06:01 AM Z


I don't remember if any of these
> books actually says
> that chrome alum hardens better than potassium alum

>He also says the potassium (colorless) alum keeps
> its hardening properties
> >much better than chrome alum....
and...
> Many of the older resource books on carbon recommend
> the use of
> chrome alum for single transfer supports and
> potassium alum for
> double transfer. I don't remember if any of these
> books actually says
> that chrome alum hardens better than potassium alum

Yes there is direct claims for this...From memory, I
recall it is claimed that Chrome Alum HARDENS gelatin
but the ordinary alum simply raises the "melting"
temperature (that is, the temperature at which the
gelatin GEL becomes a SOL. So, actually, the material
I have seen says Potassium alum does NOT make the
gelatin insoluble, just harder to melt, This, however,
could a relative statement...your own experience may
vary....

Fritz

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