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put the can of sweetened condensed milk in a bot full of boiling water. make sure the can is completely covered with water at all times. i heard that the can could explode if it is not completely covered. i was a little paranoid when i heard that and kept running to the kitchen if i heard any suspicious sounds. i kept a pitcher full of water nearby so i could quickly add water to the pot if needed. boil for 2-4 hours.