Method of making article with visual effect

A method for making a blow molded article from a preform, the method comprising the following steps:

• a) providing a preform of a thermoplastic material having a plurality of effect structures each having an effect surface having a normal with an orientation, the preform having a body with one or more walls and an opening, wherein at least a portion of the one or more walls of the preform has a three-dimensional pattern of cavities and/or protrusions thereon;
• and
• b) blow molding the preform to form a blow molded article, wherein the step of blow molding the preform changes the orientation of the normal of at least some of the effect surfaces of the effect structures to create a visual effect in at least one wall of the blow molded article;
• wherein the orientation of the normal of at least some of the effect surfaces is changed according to a predetermined pattern.