Commonly oxalic acid is recommended to acid treat paper but calcium oxalate is very insoluble - which never made sense to me (marble sculptures were often treated with oxalic acid to give them a protective shinny insoluble coating). I was wondering if it could be also used as a general clearing agent for all siderotypes. I am using mostly Pd and HCl is not useable. I am presently using citric acid and/or di Sodium EDTA as the first clearing baths.