View Full Version : Alum
01-22-2007, 11:35 PM
The book I am reading (the book of photograhic alternative processes)suggests using Alum as a hardener in gelatin when sizing paper. What is Alum? Is it Aluminum Potassium Sulfate? I hate it when authors are unclear...
01-22-2007, 11:46 PM
Hmmmm, I think it may also be reffering to Chromium Aluminum Sulfate, commonly called Chrome Alum.
I think either version will work, regardless.
If nothing else is specified, "Alum" is supposed to mean Potassium Aluminium Sulfate.
Unfortunately this is not always true in photographic literature.
Read http://en.wikipedia.org/wiki/Alum for more info on the various alums.
BTW, Chromium Alum is not CrAl-sulfate, but KCr-sulfate.