A curable formaldehyde-free binding composition for use with fiberglass is provided. Such curable composition comprises an addition product of an amine and a reactant to form an amino-amide intermediate. To the amino-amide is added an aldehyde or ketone to form the curable binder composition. The composition when applied to fiberglass is cured to form a water-insoluble binder which exhibits good adhesion to glass. In a preferred embodiment the fiberglass is in the form of building insulation. In other embodiments the product is a microglass-based substrate for use in a printed circuit board, battery separator, filter stock, or reinforcement scrim.