Quote Originally Posted by Niebylsamwlesie View Post
By mistake I exposed Ilford HP5 Plus 400 as ISO 12 :-(

Do you have any idea how to rescue that film? It means how develop it.


Not an expert by any means but my best bet is to use very diluted rodinal (if you have any) something like 1:400 and develop by inspection. If the developer loses strength before the desired development level, add fresh 1:400 solution.

You can always use a reducer afterwards.