The Dye-Pen Crack Detection System is a 3-part system to visually check for cracks in a weld once it has been completed. The Cleaner is used first to remove any residue from the area, then the Penetrant is applied. This will enter any cracks in the surface of the workpiece. The Cleaner is then used again to remove the excess Penetrant, and finally the Developer is applied. This brings any Penetrant in cracks to the surface where they are clearly visible and can be remedied.