I had a similar problem over the weekend...I'd used "wash-out" blue chalk with a Pounce, but the blue didn't all wash out. I contacted the manufacturer and she suggested I dab the areas with a 50/50 solution of white vinegar and water. I used a soft toothbrush to apply it. While wetting the quilt with the liquid it wasn't apparent that it was working (perhaps because the chalk had seeped into the batting) but when it was dry the blue was no longer visible. YAY!