The present invention relates to the field of environmentally friendly fountain solutions for wet offset printing processes based on oxidative drying inks. In particular, the invention related to the field of wet offset printing processes for producing security features on security documents. The present invention provides a process for producing a security feature by a wet offset printing process, said process being carried out by using a fountain solution comprising one or more manganese (II) salts of a C1-C3 carboxylic acid as well as the fountain solution and its concentrate.