fig2 there is provided a first apparatus 50 for performing the method of the invention the web 10 is conveyed over a roller 52 in a direction a adjacent the roller 52 is provided a movable roller 54 which comprises a groove not shown around its circumference the pressure and therefore the shear force can be adjusted via a spring that is mounted to a lever the groove is sized so as to receive and guide a thread 20 which is spooled around the circumference of the movable roller 54 by a first bobbin 56 and a second bobbin 58 such that a portion e g at least half or less than half of the thickness of the thread 20 is proud of the groove for engagement with the surface of the layer of first material 14 a bath 60 is provided between the first bobbin 56 and the movable roller 54 to apply solvent or other materials to the thread 20 in use the thread 20 is wound in a direction b from the first bobbin 56 through the chemical bath 60 around the movable roller 54 and onto the second bobbin 58 the movable roller 54 is moved towards the web 10 so as to engage the thread 20 with the web 10 to remove at least a portion of the layer of first material 14 the speed of movement of the thread in direction b may be adjusted in order to obtain optimal patterning results a more complete version of the above discussed system is.