This white ‘Clover’ brand pen contains a milky looking waxy substance. When marking, a light pressure must be used for the white ‘ink’ to flow easily. About 20 seconds after marking a thin white line appears. To “erase” the mark heat needs to be applied. One quick touch with an iron and poof, no mark.
The pen should NOT be stored in an area that has the tendency to bake in the sun, or be heated overly. I’ve found to my chagrin that the ‘ink’ of the pen seperates into a transparent liquid with a solid mass of white if left in a super hot car...
The only time I’ve seen the wax leave any sort of mark after being ironed away, my fabric was a stark black batik that showed a slightly darker line when the marks were ironed off. This has only happened once to me, and the mark was easily removed with a light soapy scrub with a damp cloth.
I’ve owned dozens of these pens throughout the years and recommended them to my students in several of my classes.
The pens are particularly useful when drawing needle turn appliqué patterns on fabric. Something about the waxy stuff makes needle turn appliqué easier, as the wax tends to cause the fabric to naturally bend one the drawn line. Win win.