Make sure you grind the surface of the glass before its glassed back together,if you are using polyester,it is a mechanical bond,not a chemical bond,so it needs to have a scratched up surface to adhere to.Also, a point to remember is that when you wash up,dont use hot water,as the heat will open up the pores in your skin and the glass will go in..I use rubber medical gloves and paper overalls,and a good dust/partical mask.