"The present invention is concerned with an additive which is the condensation product of an aldehyde having at least two carbon atoms and/or a ketone and a polyamino compound of the formula: ##STR3## wherein n is 0 or an integer from 1 to 6, M is a carbon or nitrogen atom and R1, R2, R3 and R4 are independently hydrogen, a saturated or unsaturated hydrocarbon group, e.g., alkyl, aryl, aralkyl, alk" . . . .