The subject often comes up about these pens. Usually the quilter is concerned that the marks didn't totally disappear. In many of the cases the quilter describes removing the marks by either wiping with a wet cloth or spritzing with water. Such techniques for removing the marks may be the recommendation of the manufacturer but they don't always work. It is my belief and always recommendation that when using these water erasable pens the finished quilt be completely washed when it is finished. There have been reported cases that with spritzing and wiping with wet cloth, that although the lines do disappear eventually they return - although faint. I also believe that while the surface color might appear to be removed that the color in the ink migrates into the batting and could reappear at some time. It is always safer to wash and not take the chance the marks will return
I believe this is especially important when using the water pen that disappear in the air. (Must be fast quilters who ue these.) While the lines do disappear in time, the chemical is still in the fabric. Again, better to wash out than be disappointed.