When marking dark fabrics, I prefer to use the pen made by Clover - "White Marking Pen (Fine)". As you make your lines, you see nothing. Wait about ten seconds and your line will appear and will stay and stay and stay until you either spritz it with water or touch with an iron. It is a little pricey ($5-6) for a pen but well worth the investment. -- I believe Dritz has attempted to copy it, but I found it very unsatisfactory. Go with the Clover. Suzanne