I do use my black Frixion pen for small projects and I pre-test it before drawing on darker fabrics. I will not use it on a big quilt because of the mark reappearing in cold conditions. I may do a test at some time on it to see if it washes out if you put the quilt through the wash and dryer. For marking on dark fabric, I like my white chalk Fons&Porter pump pencil. It does have to be washed out but it makes a nice thin line that I can see on a dark fabric. Always test a marking product on a scrap before using it on a quilt!