I'm having serious issues with the XCR resin getting white lines in the surface when sanding a skinned and coated parts. I'm confident that I have not made any errors in mixing or application. It would seem that the lines are formed by poor bond between the layers. While they get better as you go through the grits they dont seem to disappear and remain visible after buffing

You may well be leaving it slightly too long between subsequent coats or if going past B stage, not sanding the part coarsely enough for the resin to bond properly.  

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant