A method of forming a security device component comprising: providing a support layer and a casting relief structure; applying a curable material to a surface across a surface region (114,115) of the support layer or the casting relief structure using an application device, the application device being adapted to transfer the curable material onto the surface in a first sub-region of the surface region with a first average volume per unit area and to transfer the material onto the surface in a second sub-region of the surface region with a second average volume per unit area, wherein the curable material in the second sub-region abuts the curable material in the first sub-region, wherein the curable material in the second sub-region provides at least one lateral edge of the curable material across the surface region, and wherein the second average volume per unit area is less than the first average volume per unit area; wherein the surface is either a surface of the support layer or a casting surface of the casting relief structure; bringing the casting relief structure and the support layer together across the surface region such that the curable material lays therebetween; curing the curable material, thereby fixing a surface relief structure in the surface of the cured curable material; and separating the casting relief structure and the support layer such that the cured curable material is carried by the support layer; whereby the cured curable material applied in the first sub-region of the surface region carries a primary portion of the surface relief structure, the primary portion of the surface relief structure corresponding to at least a part of the casting relief structure in the casting surface, and the cured curable material applied in the second sub-region of the surface region carries an ancillary portion of the surface relief structure, the ancillary portion of the surface relief structure having a thickness that decreases from the primary portion of the relief structure towards a lateral edge of the cured curable material. providing a support layer and a casting relief structure; applying a curable material to a surface across a surface region (114,115) of the support layer or the casting relief structure using an application device, the application device being adapted to transfer the curable material onto the surface in a first sub-region of the surface region with a first average volume per unit area and to transfer the material onto the surface in a second sub-region of the surface region with a second average volume per unit area, wherein the curable material in the second sub-region abuts the curable material in the first sub-region, wherein the curable material in the second sub-region provides at least one lateral edge of the curable material across the surface region, and wherein the second average volume per unit area is less than the first average volume per unit area; wherein the surface is either a surface of the support layer or a casting surface of the casting relief structure; bringing the casting relief structure and the support layer together across the surface region such that the curable material lays therebetween; curing the curable material, thereby fixing a surface relief structure in the surface of the cured curable material; and separating the casting relief structure and the support layer such that the cured curable material is carried by the support layer; whereby the cured curable material applied in the first sub-region of the surface region carries a primary portion of the surface relief structure, the primary portion of the surface relief structure corresponding to at least a part of the casting relief structure in the casting surface, and the cured curable material applied in the second sub-region of the surface region carries an ancillary portion of the surface relief structure, the ancillary portion of the surface relief structure having a thickness that decreases from the primary portion of the relief structure towards a lateral edge of the cured curable material.