Quote Originally Posted by Tofek View Post
I bought some Tetenal Hardener to add in Ilford Rapid Fixer, but I just read on the net that those two aren't compatible. Does anyone know what fixers are compatible with this hardener ? And just for curiosity, why some aren't ?

Thanks in advance,

Basically if the hardener is too acidic then it could trigger sulfur colloidal precipitation out of the fixer.
Tetenal Harter's acidity is calibrated to be used only with Tetenal acidic fixer.