A method of producing a diffractive optical element comprises forming on a textured surface of a first substrate (2) a predetermined pattern of an ink (3) including an activator for a metallisation reaction and one or more binders; causing or allowing the binder to solidify; applying a first adhesive layer (4) on top on the solidified binder and activator; securing a second substrate (5) to the adhesive layer; removing the second substrate with adhered solidified binder and activator from the first substrate; and forming a metal coating (10) onto the activator-containing regions adhered to the second substrate.