Tuff Break is the name of “That Rubber Stuff” I use to set my cloisonné enamel jewels. For several reasons in all my settings of enamels jewelry. One it adds protect the counter enamel while setting, by giving the enamel piece a cushion which help me not crack the piece during the process of closing the bezel over the delicate enamel edge. Secondly, it removes that clingy sound of the enamel against the metal once the piece is complete.
Many enamelist use glues or a piece of plastic behind the enameled piece and even sawdust. I feel this adds a more professional element to the cloisonné jewel.
See my setting cloisonné enamel jewels https://alohilanidesigns.com/setting-cloisonne-enamels/ and you will get a better picture what I an sharing here.
I sell Tuff Break on Croft Kiln site http://croftkilns.com/accessories/