I am sorry, if you have already tried this. I do machine embroidery, and use spray adhesive on the hoops, they also get very sticky. To clean them I run warm soapy water in sink or any vessel your stencil will fit into and let it soak sometimes for hours. But, it does get where you can wipe them right off. I have heard not to use rubbing alcohol to clean plastic hoops, because this dries them out. Maybe worth a try. Good luck.