Alum

Andrew O'Neill

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• Jan 23, 2007

• #1

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...

 

Dana Sullivan

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• Jan 23, 2007

• #2

Hmmmm, I think it may also be reffering to Chromium Aluminum Sulfate, commonly called Chrome Alum.

I think either version will work, regardless.

 

Ole

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• Jan 23, 2007

• #3

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.