Preparing the Bottle for Re-Clayification

One fault from the previous attempt was a weak bond between the glass, the glue, and the clay. I am fixing that issue by scratching the glass (to create a more abrasive surface) and will attach metal rods to the bottom. Those metal rods will be wrapped around the clay and hold it in place. Since the bottom of the bottle will be completely covered by paint, the scratches will be very difficult to see (also, who looks at the bottom of a ship-in-a-bottle?).