I purchased a Dritz chalk holder with different colored chalk pieces to use to mark stitch lines. I tried it on a scrap and it seemed okay. I guess I must have pressed harder on the real thing as it still shows even after I have rubbed the lines repeatedly. The chalk lines are yellow. Do I dare try to wash them off with a moist cloth or will that only "set" them? The quilt is for me so I could wash it if that is the solution, I'm just worried that whatever I do will make them permanent. Please help! Thanks