I have made a few batches of container candles using my beginner's kit purchased from Lone Star. The kit comes with IGI 4636 which is described as a single pour wax. Every batch I've made so far has required a second pour to account for shrinkage. I melt the wax to 180° and then add color dye and FO. I remove the melting pot from the double boiler, stir the mixture for 3 minutes, and pour the candles. I've also tried to cool the wax to 150° before pouring with the same result. What am I doing wrong?