if an eraser does not work contact Fons & Porter thru the web site- they will help you- if you (heat set it) you may have a lasting problem- it is always very important to follow the instructions completely---and test before using any marking tool- sometimes the difference between pre-washed & not washed fabrics can make a difference---you may find oxyclean paste will help- but before doing too much i would find out what the instructions for the specific item say---then contact them for help.