Re: dichromated colloids

MARTINM wrote:
>
> "This is interesting to me in the context of reading a paper today that
> claims that some of Eder's results were due to impurities in the gelatin."
>
> Taking into account the complexity of the chemical structures of gelatin and
> gum, I wonder if it's not next to impossible to get standardized gum or
> gelatin (at least in respect to photographic applications). .
>

This is what I was trying to say to Sandy a while back and couldn't make
myself understood, in the context of percent solution of gum. I notice
in one of the articles I read today that as far back as 1930,
researchers knew that percent solution of gelatin is not a useful
measure and that "in order to obtain results truly comparable with each
other the estimations should be carried out on solutions containing
equal concentrations of nitrogen." (Galinsky, 1930).

And maybe the
> vagueness, lack of reliability we generally attribute to those past formulas
> taken from old photographic books actually relates to that deficit.
>

This is why I've always said that the person who learns to print gum by
feel has a leg up over one who just goes by measuring. It's like making
bread: if you measure out the same amount of flour every day, some days
you'll make good bread and some days you'll make not so good bread. But
if you go by the feel of the dough instead of by the measure, you'll
make perfect bread every day.
Katharine
kt
Received on Fri May 21 05:52:05 2004