The invention provides method for producing a 3D item (1) by means of fused deposition modelling, the method comprising: —a 3D printing stage comprising layer-wise depositing an extrudate (321) comprising 3D printable material (201), wherein during at least part of the 3D printing stage the extrudate (321) comprises a core-shell extrudate (1321) comprising a core (2321) comprising a core material (2011), and a shell (2322) comprising a shell material (2012), to provide the 3D item (1) comprising 3D printed material (202), wherein the 3D item (1) comprises a plurality of layers (322) of 3D printed material (202), wherein one or more of layers (322) comprises one or more core-shell layer parts (3322), wherein each of the core-shell layer parts (3322) comprises a layer core (3321) comprising the core material (2011), and a layer shell (3322) comprising the shell material (2012), wherein the 3D item (1) has an item surface (252) defined by at least part of the 3D printed material (202); —an exposure stage comprising exposing at least part of the item surface (252) to a liquid (402), wherein the core material (2011) has core material solubility SC1 for the liquid (402) and wherein the shell material (2012) has a shell material solubility SS1 for the liquid (402), wherein SC1