Invisible Ink Pen High Quality Permanent Invisible Ink Here is the perfect ink for identification marking. Glows an incredible bright blue. Perfect for metal, glass, plastics etc,. Totally invisible, won't wash off only visible with Blacklight. This is the pen you want for permanent marking. We have tested this ink against other pens and found them to wash off too easily compared to our formula. Fine point tip for specialy making such as circuit boards. Glows a bright blue under black light/ UV. NOT suitable For Hand/Skin Marking