Open the to of the milk cartons to form rectangular boxes. Grease or spray inside of cartons. Fill the cartons with the following five layers: shells, ice, shells, ice, and shells. Place a birthday candle in the center of the carton with wick exposed (shells and ice will hold it in place) Slowly pour melted parafwax into each carton until the wax is approx. 1/8 inch from the exposed wick. Allow to cool completely, even overnight. Tear away carton. (NOTE there will be water spillage due to trapped water in the carton, so complete this step over a sink or outside) Display the candles.