Hmmm ... this is completely off the topic, but I seem to remember dumping some
ammonium aluminum sulfate in a glass of water back when I was in high school.
The result, was lots of bubbles (The ammonia vapor perhaps?), and a gelatinous
precipitate. I seem to remember reading later that this was sometimes used in
water purification since the gas would kill bacteria, and the precipitate would
trap and carry suspended particles to the bottom.
To get back on topic. The only place for alum in carbon printing, as far as I
know anyway, is for hardening the gelatin size. I also seem to remember
reading, on this list some time ago, that alum sizing may lower the paper's pH,
and hence be less archival. I haven't been able to locate that in the archives
though.
- Wayde Allen
(74160.3410@compuserve.com)