Hardener Chemistry Question

[newcan1]

I want to make a hardening fixer from a formula that calls for Potassium Alum (which I understand to be Potassium Aluminum Sulfate). I only have Aluminum Sulfate. Can I substitute? If I do, should I also add Sodium Sulfate (which I also have)? If so, any ideas as to substitution quantities?

I have some Potassium Alum on order, but it won't be here for a couple of days, so I got to thinking.

 

[newcan1]

I am kind of guessing that if I added about half the quantity of each compared to the formula, that I would end up in the right place, more or less (except with sodium ions instead of potassium). I am not a chemical engineer though!

 

[dE fENDER]

You can substitute them, but be aware that pH with aluminium sulfate can be lower than with alum, so it is possible to get some precipitiation (of sulfur or aluminium salts) in solution. Check in small quantities first.

 

[tezzasmall]

I have some Potassium Alum on order, but it won't be here for a couple of days, so I got to thinking.

I use a VERY SMALL amount at a time of Potassium Alum, which I use with liquid emulsion when I coat watercolour paper for printing on. It's crystals are a beautiful colour and it does the job of hardening very well for the little amount required.

I don't know about the other chemicals you have already so I can only recommend that you wait a day or two for the correct chemical as it does the job well.

All the best,

Terry S