Plastics can contain various plasticisers that prevent the edding varnish from binding with the surface. We can only give you very general instructions on how to use "plastic", as it is not possible to test the ink on all surfaces. edding Permanent Spray Plastic Primer could be a possible solution. edding Plastic Primer forms a bridge between the plastic surface and the subsequent layer of paint. We recommend that you test the application on an inconspicuous area.