A wet-on-wet process for producing multicoat color and/or effect coating systems is disclosed. The process involves using aqueous functional coating materials comprising

(A) at least one crosslinkable binder,

(B) at least one separate, water-soluble and/or -dispersible crosslinking system which independently effects partial or complete crosslinking in and/or on the matrix of the wet, drying and/or dried films (2) of the aqueous functional coating materials before the binders (A) crosslink completely; and

(C) at least one pigment.