The invention provides a method for producing a 3D item (1) by means of fused deposition modelling, the method comprising a 3D printing stage, wherein the 3D printing stage comprises a reflective material deposition stage, wherein the reflective material deposition stage comprises: (A) providing 3D printable material (201) comprising (i) a polymeric matrix material (211) that is transmissive for UV radiation, especially wherein the polymeric matrix material (211) comprises thermoplastic material, and (ii) a reflective material (212) that is reflective for the UV radiation and that is at least partly enclosed by the polymeric matrix material (211); wherein the reflective material (212) comprises a first fluoropolymer; and (B) depositing the 3D printable material (201), to provide the 3D item (1) comprising 3D printed material (202) comprising the matrix material (211) and the reflective material (212).