The plastic surfaces can be further embellished with coatings to match the current fashion. Galvanising or vacuum steaming can even give a metallic look to plastic products. The various coatings, adhesives and inks used on the surface of plastic products do not adhere well to the smooth, mostly unpolar plastic surface. In order to improve adhesion, various surface treatments are therefore used to change the chemical composition of the surface (making it more polar) or, in some cases (e.g. gluing), to roughen it slightly.