I think I know which kind of chalk pencil you are talking about and I have one. I made a fall quilt with loads of different colors and I used almost every color of chalk lead when I marked the quilt so I could see my marks on all the different colors. I am a prewasher so I just loaded the quilt in the washer when done with NO SOAP. Set it on cold and ran the washer. I carefully inspected the quilt when it came out, before putting it in the dryer. There were no marks left at all.