Begin by peeling the label off the bottle. Wash it thoroughly under running water. Use a brush to remove any stubborn glue or debris.
Place the bottle in the bag, and make sure to close the bag securely. Smash the bottle into small pieces with a hammer. Use a spoon to move the glass from the bag into the mold of the kiln.
Heat the kiln to 500 degrees Fahrenheit and let the glass sit in that temperature for about 10 minutes. Raise the temperature to 1,000 degrees Fahrenheit and let the glass sit for another 10 minutes. Finally, raise the temperature to 1,425 degrees Fahrenheit. The glass should have melted into the shape of the mold in which you placed it.
Do not touch the glass until the kiln is below 100 degrees Fahrenheit. Once it is cool enough, carefully remove the glass from the kiln and the mold.